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1.  Long-Term Survival in a Large Cohort of Patients with Venous Thrombosis: Incidence and Predictors 
PLoS Medicine  2012;9(1):e1001155.
Linda Flinterman and colleagues report on the long-term mortality rate for individuals who have experienced a first venous thrombosis or pulmonary embolism. They describe an ongoing elevated risk of death for individuals who had experienced a venous thrombosis or pulmonary embolism as compared to controls, for up to eight years after the event.
Background
Venous thrombosis is a common disease with a high mortality rate shortly after the event. However, details on long-term mortality in these patients are lacking. The aim of this study was to determine long-term mortality in a large cohort of patients with venous thrombosis.
Methods and Findings
4,947 patients from the Multiple Environmental and Genetic Assessment study of risk factors for venous thrombosis (MEGA study) with a first nonfatal venous thrombosis or pulmonary embolism and 6,154 control individuals without venous thrombosis, aged 18 to 70 years, were followed up for 8 years. Death and causes of death were retrieved from the Dutch death registration. Standardized mortality ratios (SMRs) were calculated for patients compared with control individuals. Several subgroups were studied as well.
736 participants (601 patients and 135 controls) died over a follow-up of 54,948 person-years. The overall mortality rate was 22.7 per 1,000 person-years (95% CI 21.0–24.6) for patients and 4.7 per 1,000 person-years (95% CI 4.0–5.6) for controls. Patients with venous thrombosis had a 4.0-fold (95% CI 3.7–4.3) increased risk of death compared with controls. The risk remained increased up to 8 years after the thrombotic event, even when no additional comorbidities were present. The highest risk of death was found for patients with additional malignancies (SMR 5.5, 95% CI 5.0–6.1). Main causes of death were diseases of the circulatory system, venous thrombosis, and malignancies. Main limitation was a maximum age of 70 at time of inclusion for the first event. Therefore results can not be generalized to those in the highest age categories.
Conclusions
Patients who experienced a first venous thrombosis had an increased risk of death which lasted up to 8 years after the event, even when no comorbidities were present at time of thrombosis. Future long-term clinical follow-up could be beneficial in these patients.
Please see later in the article for the Editors' Summary
Editors' Summary
Background
The term venous thrombosis describes the clinical situation—more common during pregnancy, after surgery, or serious illness—in which a blood clot lodges in a vein. One specific type, which is more serious, involves the clot forming in a major vein in the lower leg and thigh and is termed a deep venous thrombosis. The clot can block blood flow and cause swelling and pain, but more seriously, can break off and move through the bloodstream, causing an embolism. An embolism can get stuck in the brain (and cause a stroke), lungs (and cause a pulmonary embolism), heart (to cause a heart attack), and/or other areas of the body, leading to severe damage.
Venous thrombosis is known to be associated with considerable short-term morbidity and mortality: the mortality rate after venous thrombosis is about 20% within one year and studies to date have suggested that the mortality rate is two to four times higher for patients with pulmonary embolism, of whom 10%–20% die within three months after the event. Many factors are associated with venous thrombosis, and the underlying cause of the thrombosis affects survival; for example, those with thrombotic events provoked by surgery or trauma have a lower mortality risk than patients with thrombosis caused by malignancy. Furthermore, about 10%–20% of patients who have had a venous thrombosis develop a recurrence within five years and up to 50% develop post-thrombotic syndrome—long-term swelling, pain, and changes in skin color.
Why Was This Study Done?
It is currently unknown whether the poor prognosis associated with venous thrombosis is limited to the months following the thrombotic event, or persists for years afterwards. So in this study, the researchers sought to answer this question by analyzing the long-term survival in a large cohort of patients who had experienced a first venous thrombosis and who were all followed for up to eight years.
What Did the Researchers Do and Find?
The researchers used the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis study (MEGA study), which was a case-control study involving 4,965 consecutive patients aged 18 to 70 years who were objectively diagnosed with a deep venous thrombosis or pulmonary embolism and recruited from six anticoagulation clinics in the Netherlands between March 1999 and September 2004. The control group consisted of partners of patients (n = 3,297) and a random control group matched on age and sex (n = 3,000). The researchers obtained causes of death from the Central Bureau of Statistics and for the observation period (30 days after the venous thrombosis, to either death or end of follow-up between February 2007 and May 2009) compared cause-specific death rates of the patients to those of the general Dutch population. The researchers devised specialist survival models (called Kaplan-Meier life-tables) and calculated standardized mortality ratios (SMRs—the ratio of the observed number of deaths over the number of deaths expected) to estimate relative rates of all cause mortality by type of the initial thrombosis and the underlying cause.
Using these methods, the researchers found that the overall mortality rate in patients with thrombosis was substantially greater than in the control group (22.7 per 1,000 person-years compared to 4.7 per 1,000 person-years). Apart from malignancies, the researchers found that the main causes of death were diseases of the circulatory and respiratory system. Patients with venous thrombosis and malignancy had the highest risk of mortality: 55% died during follow-up. Patients with venous thrombosis without malignancy had an overall 2-fold increased risk of mortality compared to the control group and this risk was comparable for patients with different forms of thrombosis (such as deep venous thrombosis and pulmonary embolus). According to the researchers' calculations, the relative risk of death was highest during the first three years after thrombosis, but for those with thrombosis of unknown cause, the risk of death increased by two-fold up to eight years after the thrombosis. Furthermore, the researchers found that the highly increased risk of death for those with pulmonary embolism is mainly only for the first month as long-term survival is similar to that of patients with a deep venous thrombosis.
What Do These Findings Mean?
These findings show that patients who have experienced a venous thrombosis for the first time have an increased risk of death, which may last up to eight years after the event. These findings have important clinical implications and suggest that long-term clinical follow-up could be beneficial in patients who have experienced a venous thrombosis for the first time.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001155.
Wikipedia provides information about venous thrombosis note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
Medline has patient-friendly information about deep venous thrombosis and pulmonary embolism
doi:10.1371/journal.pmed.1001155
PMCID: PMC3254666  PMID: 22253578
2.  Synergistic Effects of Hypofibrinolysis and Genetic and Acquired Risk Factors on the Risk of a First Venous Thrombosis 
PLoS Medicine  2008;5(5):e97.
Background
Previously, we demonstrated that hypofibrinolysis, a decreased capacity to dissolve a blood clot as measured with an overall clot lysis assay, increases the risk of venous thrombosis. Here, we investigated the combined effect of hypofibrinolysis with established risk factors associated with hypercoagulability.
Methods and Findings
Fibrinolytic potential was determined with a plasma-based clot lysis assay in 2,090 patients with venous thrombosis and 2,564 control participants between 18 and 70 y of age enrolled in the Multiple Environmental and Genetic Assessment (MEGA) of risk factors for venous thrombosis study, a population-based case-control study on venous thrombosis. Participants completed a standardized questionnaire on acquired risk factors.
Hypofibrinolysis alone, i.e., clot lysis time (CLT) in the fourth quartile (longest CLT) (in absence of the other risk factor of interest) increased thrombosis risk about 2-fold relative to individuals with CLT in the first quartile (shortest CLT). Oral contraceptive use in women with CLT in the first quartile gave an odds ratio (OR) of 2.6 (95% confidence interval [CI] 1.6 to 4.0), while women with hypofibrinolysis who used oral contraceptives had an over 20-fold increased risk of venous thrombosis (OR 21.8, 95% CI 10.2 to 46.7). For immobilization alone the OR was 4.3 (95% CI 3.2 to 5.8) and immobilization with hypofibrinolysis increased the risk 10.3-fold (95% CI 7.7 to 13.8). Factor V Leiden alone increased the risk 3.5-fold (95% CI 2.3 to 5.5), and hypofibrinolysis in factor V Leiden carriers gave an OR of 8.1 (95% CI 5.3 to 12.3). The combination of hypofibrinolysis and the prothrombin 20210A mutation did not synergistically increase the risk. All ORs and 95% CIs presented are relative to individuals with CLT in the first quartile and without the other risk factor of interest.
Conclusions
The combination of hypofibrinolysis with oral contraceptive use, immobilization, or factor V Leiden results in a risk of venous thrombosis that exceeds the sum of the individual risks.
Frits Rosendaal and colleagues show that the combination of hypofibrinolysis with oral contraceptive use, immobilization, or factor V Leiden results in a risk of venous thrombosis that exceeds the sum of the individual risks.
Editors' Summary
Background.
When a blood vessel is injured, proteins in the blood called clotting factors “coagulate” (solidify) the blood at the injury site. The resultant clot (thrombus) plugs the wound and prevents blood loss. When the injury has healed, other proteins dissolve the clot, a process called “fibrinolysis.” Sometimes, however, a thrombus develops inside an undamaged blood vessel and partly or completely blocks the blood flow. A clot that occurs in one of the veins (vessels that take the blood to the heart) deep within the body (usually in the leg) is a deep vein thrombosis (DVT). Some DVTs have no symptoms; others cause pain, swelling, and tenderness in one leg. They are usually treated with heparin and warfarin, anticoagulant drugs that stop the clot growing. If left untreated, part of the clot (an embolus) can break off and travel to the lungs, where it can cause a life-threatening condition called a pulmonary embolism (PE).
Why Was This Study Done?
Most people are very unlikely to develop venous thrombosis (the collective term for DVT and PE), but anything that makes blood “hypercoagulable” (prone to clotting) increases this risk. Genetic risk factors can be inherited changes in blood clotting proteins (for example, a mutation in a gene coding for one protein, factor V, which is involved in clotting, is known as factor V Leiden—Leiden, The Netherlands, was where it was first described). There are also acquired risk factors such as taking oral contraceptives or being immobilized (for example, during bed rest). These risk factors often act in such a way that the risk of developing venous thrombosis for a person with multiple risk factors is greater than the sum of the individual risks. Another recently identified but little studied risk factor for venous thrombosis is “hypofibrinolysis,” a decreased capacity to dissolve blood clots. In this study (part of the “MEGA” study on risk factors for venous thrombosis), the researchers investigate the combined effect of hypofibrinolysis and established risk factors associated with hypercoagulability on the risk of developing venous thrombosis.
What Did the Researchers Do and Find?
The researchers collected blood from more than 2,000 individuals after their first DVT or PE and from a similar number of persons without venous thrombosis (controls). For each blood sample, they measured the time it took to dissolve a clot generated from that blood in a test tube (the clot lysis time or CLT) and determined which participants had the factor V Leiden mutation or a genetic change in the clotting factor prothrombin that also increases blood coagulability. The study participants also completed a questionnaire about acquired risk factors for venous thrombosis. The researchers divided the participants into four equal-sized groups (quartiles) based on their CLT and used the quartile with the lowest CLT as the reference group for their statistical analyses; hypofibrinolysis was defined as a CLT in the highest quartile (the longest times). Participants with hypofibrinolysis alone were twice as likely to develop venous thrombosis as those with a CLT in the lowest quartile (the shortest times). Oral contraceptive use alone increased the risk of venous thrombosis 2.5-fold, whereas the combination of oral contraceptive use and hypofibrinolysis increased the risk 20-fold. The researchers also found synergistic effects on thrombosis risk for hypofibrinolysis combined with immobilization or with the factor V Leiden mutation but not with the prothrombin mutation.
What Do These Findings Mean?
These findings confirm that persons with hypofibrinolysis and hence longer CLTs have a greater risk of developing venous thrombosis than those with short CLTs. Because CLTs were measured after venous thrombosis had occurred, hypofibrinolysis could be an effect rather than a cause of this condition. However, this is unlikely because there was no association between how long after the venous thrombosis the blood sample was taken and the measured CLT. These findings also show that the combination of hypofibrinolysis with immobilization, the factor V Leiden mutation, and oral contraceptive use greatly increases the risk of venous thrombosis. This new information about the risk factors for venous thrombosis should help physicians to advise patients about reducing their chances of developing this life-threatening condition.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050097.
The MedlinePlus encyclopedia has pages on blood clots, deep vein thrombosis, and pulmonary embolism (in English and Spanish)
The US National Heart Lung and Blood Institute provides information on deep vein thrombosis, including an animation about how DVT causes pulmonary embolisms
The UK National Health Service Direct health encyclopedia provides information for patients on deep vein thrombosis (in several languages)
More information about the Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis (MEGA) study is available on the Leiden University Medical Center Web site
Wikipedia has pages on coagulation and on fibrinolysis (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
doi:10.1371/journal.pmed.0050097
PMCID: PMC2365975  PMID: 18462012
3.  Prevalence of thrombophilic mutations in patients with unprovoked thromboembolic disease. A comparative analysis regarding arterial and venous disease 
Hippokratia  2012;16(3):250-255.
Background: Thromboembolic disease (TED) represents one of the main reasons of morbitity and mortality in Western World. Venous and arterial thrombotic disorders have long been viewed as separate pathophysiological entities. However, in recent times the separate nature of arterial and venous thrombotic events has been challenged. Although inherited thrombophilia’s predominant clinical manifestation is venous thrombosis, its contribution to arterial thrombosis remains controversial. Purpose  of  the  study  was  to  evaluate  the  prevalence  of  the  most common  thrombophilic  mutations, FV Leiden G1691A-FVL and FII G20210A-PTM and to assess  the  differences between venous, arterial and mixed thrombotic events. Testing  for polymorphism MTHFR C677T and  antithrombin,  protein  C  and  protein  S was also performed. Correlations with  dyslipidemia, smoking, obesity, homocysteine and antiphospholipid antibodies were made.
Methods: 515 patients with unprovoked TED, 263 males, median age 44 years, were studied. Patients were divided into three groups: 258 with venous thrombosis (group A), 239 with arterial (group B) and 18 with mixed episodes (group C). All patients were interviewed regarding family history of TED, origin, smoking and dyslipidemia. Body mass index (BMI) had been calculated. Molecular assessment of the FVL, PTM and MTHFR C677T was performed. Antithrombin, protein C, protein S, APCR, homocysteine, antiphospholipid antibodies and lipid profile were also measured.
Results: The population studied was homogenous among three groups as regards age (p=0.943), lipid profile (p=0.271), BMI (p=0.506), homocysteine (p=0.177), antiphospholipid antibodies (p=0.576), and positive family history (p=0.099). There was no difference in the prevalence of FVL between venous and arterial disease (p=0.440). Significant correlation of PTM with venous TED was found (p=0.001). The number of positive and negative for MTHFR presented statistically significant difference with a support in arterial disease (p=0.05). Moreover, a 2-fold increase in the risk of venous thrombosis in FVL positive patients (odds ratio: 2.153) and a positive correlation of homocysteine levels with MTHFR C677T (p<0.001) was found.
Conclusions: Correlation of PTM with venous thrombosis was established. Analysis showed no difference in prevalence of FVL between venous and arterial thrombosis, indicating that FVL might be a predisposing factor for arterial disease. A significant increase in MTHFR C677T prevalence in arterial disease was found. In conclusion, young patients with unprovoked arterial disease should undergo evaluation for thrombophilic genes. Identification of these mutations is important in the overall assessment and management of patients at high risk. Findings will influence the decisions of stratified approaches for antithrombotic therapy either primary or secondary thromboprophylaxis, the duration of therapy, the potential for avoiding clinical thrombosis by risk factor modification and the genetic counselling of family members. However, further studies are needed to clarify the nature of the association regarding venous and arterial thrombotic events.
PMCID: PMC3738733  PMID: 23935293
thrombophilic mutations; unprovoked thromboembolic disease; arterial thromboembolic disease; venous thromboembolic disease
4.  Travel-Related Venous Thrombosis: Results from a Large Population-Based Case Control Study (MEGA Study) 
PLoS Medicine  2006;3(8):e307.
Background
Recent studies have indicated an increased risk of venous thrombosis after air travel. Nevertheless, questions on the magnitude of risk, the underlying mechanism, and modifying factors remain unanswered.
Methods and Findings
We studied the effect of various modes and duration of travel on the risk of venous thrombosis in a large ongoing case-control study on risk factors for venous thrombosis in an unselected population (MEGA study). We also assessed the combined effect of travel and prothrombotic mutations, body mass index, height, and oral contraceptive use.
Since March 1999, consecutive patients younger than 70 y with a first venous thrombosis have been invited to participate in the study, with their partners serving as matched control individuals. Information has been collected on acquired and genetic risk factors for venous thrombosis. Of 1,906 patients, 233 had traveled for more than 4 h in the 8 wk preceding the event. Traveling in general was found to increase the risk of venous thrombosis 2-fold (odds ratio [OR] 2.1; 95% confidence interval [CI] 1.5–3.0). The risk of flying was similar to the risks of traveling by car, bus, or train. The risk was highest in the first week after traveling. Travel by car, bus, or train led to a high relative risk of thrombosis in individuals with factor V Leiden (OR 8.1; 95% CI 2.7–24.7), in those who had a body mass index of more than 30 kg/m2 (OR 9.9; 95% CI 3.6–27.6), in those who were more than 1.90 m tall (OR 4.7; 95% CI 1.4–15.4), and in those who used oral contraceptives (estimated OR > 20). For air travel these synergistic findings were more apparent, while people shorter than 1.60 m had an increased risk of thrombosis after air travel (OR 4.9; 95% CI 0.9–25.6) as well.
Conclusions
The risk of venous thrombosis after travel is moderately increased for all modes of travel. Subgroups exist in which the risk is highly increased.
In a large case-control study of travelers, the risk of venous thrombosis was increased 3-fold with a similar risk for flying or travelling by car, bus, or train.
Editors' Summary
Background.
Recently there has been increasing concern that blood clots (thromboses) in the leg or lungs occur with greater frequency after air travel. Several theories have been put forward to explain why this increase might happen, including the fact that air passengers tend to not move around much, or possibly that reduced amounts of oxygen in the blood make the blood more likely to clot. Understanding what causes such clots is important as it would help us come up with suggestions of ways to prevent them.
Why Was This Study Done?
It is not possible to test in a controlled trial whether travel causes an increase in blood clots, so the next best way of studying this problem is to do a case-control study, in which people with blood clots (cases) are compared with similar people who don't have a blood clot (controls—in this case, the partners of the cases), and the differences in a number of contributing factors are assessed.
What Did the Researchers Do and Find?
Since 1999, the MEGA (Multiple Environmental and Genetic Assessment of Risk Factors for Venous Thrombosis) study has aimed to identify all people in an area of the Netherlands who develop a blood clot for the first time, by seeking out people who receive treatment for blood clots. At the time of this report, 1,906 people with clots had been found; of these, 233 had traveled for more than four hours in the eight weeks preceding the event. Traveling in general was found to increase the risk of clots two-fold, and the risk was highest in the week after traveling. The risk of flying was similar to the risk of traveling by car, bus, or train, and was highest in the first week after traveling. Certain other factors increased the risk of a blood clot even more, such as having a particular mutation (known as factor V Leiden) in a gene involved in blood clotting, having a body mass index of more than 30 kg/m2 (over 30 kg/m2 is defined as being obese), being more than 1.90 meters tall, and using oral contraceptives. All these factors made the risk of clots especially after air travel worse; in addition, people shorter than 1.60 meters also had an increased risk of thrombosis after air travel. However, it should be borne in mind that the number of cases in each of these various groups was quite small, and the overall risk of getting a thrombosis is still low.
What Do These Findings Mean?
Since the risks of thrombosis are increased for all types of long travel, it seems that the main factor causing the thrombosis is immobility. However, since the risk is even higher for air travel, the relative lack of oxygen may also play a part. One interesting aspect of this study is that the researchers used partners as controls; in order to be sure that doing this did not make the results invalid, the researchers had to carefully adjust for differences between the cases and controls, such as the fact that partners were generally of the opposite sex. In a related Perspective (DOI: 10.1371/journal.pmed.0030300), Kenneth Rothman discusses the study further.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0030307.
MedlinePlus encyclopedia entries on deep venous thrombosis and pulmonary embolus
OMNI, a health information service in the UK run by the Resource Discovery Network, has links to pages of information on venous thrombosis
The Web site for the MEGA study in this paper gives further background and information
The Web site of the World Health Organization Research Initiative into Global Hazards of Travel has information on research into the connection between air travel and venous thrombosis
doi:10.1371/journal.pmed.0030307
PMCID: PMC1551914  PMID: 16933962
5.  Impact of sepsis on risk of postoperative arterial and venous thromboses: large prospective cohort study 
Objectives To evaluate the impact of preoperative sepsis on risk of postoperative arterial and venous thromboses.
Design Prospective cohort study using the National Surgical Quality Improvement Program database of the American College of Surgeons (ACS-NSQIP).
Setting Inpatient and outpatient procedures in 374 hospitals of all types across the United States, 2005-12.
Participants 2 305 380 adults who underwent surgical procedures.
Main outcome measures Arterial thrombosis (myocardial infarction or stroke) and venous thrombosis (deep venous thrombosis or pulmonary embolism) in the 30 days after surgery.
Results Among all surgical procedures, patients with preoperative systemic inflammatory response syndrome or any sepsis had three times the odds of having an arterial or venous postoperative thrombosis (odds ratio 3.1, 95% confidence interval 3.0 to 3.1). The adjusted odds ratios were 2.7 (2.5 to 2.8) for arterial thrombosis and 3.3 (3.2 to 3.4) for venous thrombosis. The adjusted odds ratios for thrombosis were 2.5 (2.4 to 2.6) in patients with systemic inflammatory response syndrome, 3.3 (3.1 to 3.4) in patients with sepsis, and 5.7 (5.4 to 6.1) in patients with severe sepsis, compared with patients without any systemic inflammation. In patients with preoperative sepsis, both emergency and elective surgical procedures had a twofold increased odds of thrombosis.
Conclusions Preoperative sepsis represents an important independent risk factor for both arterial and venous thromboses. The risk of thrombosis increases with the severity of the inflammatory response and is higher in both emergent and elective surgical procedures. Suspicion of thrombosis should be higher in patients with sepsis who undergo surgery.
doi:10.1136/bmj.g5334
PMCID: PMC4157562  PMID: 25199629
6.  Cancer-associated thrombosis: clinical presentation and survival 
Background
Thromboembolic events are important causes of morbidity and mortality in cancer patients. Clinical presentation in a community-based setting has not been fully clarified. The purpose of this study was to evaluate the incidence, risk factors, role of thrombophilia, and subsequent survival following thrombosis in cancer patients.
Methods
A retrospective review was undertaken of clinical data for all consecutive patients with histologically confirmed cancer seen by the author at a regional cancer center, with emphasis on cancer-related thrombosis.
Results
Between 2005 and 2012, of 1874 cancer patients, 307 (16.4%) developed thrombosis during their lifetime. Of these patients, 37 (2%) had a history of thrombosis, while the remaining 270 (14.4%) patients developed thrombosis 3 months before or any time after diagnosis of cancer, which was considered to be cancer-related. These patients included 230 (12.3%) with venous thrombosis, 28 (1.5%) cases with arterial occlusion, and 12 (0.6%) with combined venous and arterial thrombosis. Patients of Caucasian ancestry were more prone to develop thrombosis, with a higher frequency of multiple genetic thrombophilia compared with other ethnic groups. In regression analysis, only advanced stages of cancer and the presence of atherosclerosis were predictive of thrombosis. There were no significant differences between venous and arterial thrombosis. The worst survival was noted in patients who developed thrombosis 3 months prior to or shortly after their diagnosis of cancer. There has been a recent improved survival outcome following therapy.
Conclusion
In addition to venous thrombosis, arterial occlusion with stroke and anginal symptoms is relatively common among cancer patients, especially those of Caucasian ancestry, and is possibly related to genetic predisposition.
doi:10.2147/CMAR.S47094
PMCID: PMC3732200  PMID: 23926439
analyses; genetic association; embolism and thrombosis; genetic susceptibility; incidence study; venous thromboembolism; thrombophilia; hereditary
7.  Antiphospholipid antibodies and thrombosis: association with acquired activated protein C resistance in venous thrombosis and with hyperhomocysteinemia in arterial thrombosis 
Thrombosis and haemostasis  2004;92(6):1312-1319.
Summary
Although antiphospholipid antibodies (aPL) are associated with thrombosis, it is not known who with aPL is at higher risk for thrombosis. It was the aim of this cross-sectional study to investigate how thrombophilic factors contribute to venous or arterial thrombosis in aPL-positive individuals. In outpatient test centres at two tertiary care hospitals, two hundred and eight (208) persons requiring aPL testing were matched by age, gender and centre to 208 persons requiring a complete blood count. Persons were classified as aPL-positive (having anticardiolipin, lupus anticoagulant and/or anti-β2-glycoprotein I antibodies) or aPL-negative. Several thrombophilic factors were studied using logistic regression modelling. Results showed that the aPL-positive group had three-fold more events (37%) than the aPL-negative group (12%). In unadjusted analyses, clinically important associations were observed between factor V Leiden and venous thrombosis, hyperhomocysteinemia and arterial thrombosis, and activated protein C resistance (APCR) and venous thrombosis (OR, 95% CI = 4.00, 1.35–11.91; 4.79, 2.03–11.33; and 2.03, 1.03–3.97, respectively). After adjusting for recruitment group, persons with both APCR and aPL had a three-fold greater risk (OR, 95% CI = 3.31, 1.30–8.41) for venous thrombosis than those with neither APCR nor aPL. Similarly, after adjusting for hypertension, family history of cardiovascular disease, gender and recruitment group, persons with both hyperhomocysteinemia and aPL had a five-fold increased risk (OR, 95% CI = 4.90, 1.37–17.37) for arterial thrombosis compared to those with neither risk factor. In conclusion, APCR phenotype and hyperhomocysteinemia are associated with a higher risk of venous and arterial thrombosis, respectively, in the presence of aPL.
doi:10.1267/THRO04061312
PMCID: PMC3482245  PMID: 15583739 CAMSID: cams2359
Antiphospholipid antibodies; antiphospholipid syndrome; thrombosis; activated protein C resistance; hyperhomocysteinemia
8.  A Case Series of HIV-Seropositive Patients and Hypercoagulable State—Is It Difficult to Treat Even with Therapeutic Anticoagulation? 
Patients with human immunodeficiency virus (HIV) are at risk of developing thrombosis and are 8 to 10 times more likely to develop thrombosis than the general population. Moreover, if they have hypercoagulable state they can have severe thrombosis and life-threatening thrombotic events. The purpose of this retrospective study is to analyze hypercoagulable state in HIV-seropositive patients who have been diagnosed with venous thromboembolism (VTE). This study is a subgroup study of a larger cohort group of HIV-seropositive patients with VTE followed up with our vascular medicine outpatient clinic. The patients included for this study were HIV-seropositive patients with hypercoagulable state, analyzed over the past 3 years, and followed prospectively. HIV-seropositive patients with arterial thrombosis were excluded. These patients had minimum, regular follow-up of 3 months, with a Doppler scan in the beginning and last follow-up. All the patients were analyzed for hypercoagulable state and the patients selected in this study were those who were tested positive for hypercoagulable state. All patients were analyzed for age, gender, race, site of thrombosis, coagulation factors, lipid panel, type of antiretroviral treatment, past or present history of infections or malignancy, CD4 absolute and helper cell counts at the beginning of thrombosis, and response to treatment and outcome. Patients with HIV with arterial thrombosis were excluded. The study was approved by the ethics committee. Five patients were included in this study. The mean age was 47.8 years (range 38 to 58 years). All were male patients with lower limb thrombosis. Most common venous thrombosis was popliteal vein thrombosis, followed by common femoral, superficial femoral, and external iliac thrombosis. Two patients had deficiency of protein S, two had high homocysteine levels, one had deficiency of antithrombin 3, and one had increase in anticardiolipin immunoglobulin G antibody. All the patients were taking nucleoside and nonnucleoside inhibitors but only one patient was taking protease inhibitors. There was no history of malignancy but two patients had past history of tuberculosis. The mean absolute CD4 counts were 244 cells/UL (range 103 to 392 cells/UL) and helper CD4 counts were 19.6 cells/UL (range 15 to 30 cells/UL). All were anticoagulated with warfarin or enoxaparin. There was complete resolution of deep vein thrombosis only in one patient on long-term anticoagulation but there was no resolution of thrombosis in the other four patients despite of therapeutic anticoagulation for more than 6 months. All the patients are alive and on regular follow-up. Thrombosis in HIV patients is seen more commonly in middle aged, community ambulant male patients. The most common hypercoagulable state was noted as deficiency of protein S and hyperhomocysteinemia. Eighty percent of the patients did not respond to therapeutic anticoagulation.
doi:10.1055/s-0033-1334868
PMCID: PMC3709978  PMID: 24436593
deep vein thrombosis; duplex; DVT; enoxaparin; factor V Leiden; low molecular weight heparin; proximal
9.  Risk of Venous Thromboembolism in Patients Infected with HIV: A Cohort Study 
Introduction Human immunodeficiency virus (HIV) patients are at risk of developing thrombosis than general population. There are several intersecting mechanisms associated with HIV infection and antiviral therapy that are emerging, which may lead to vasculopathy and hypercoagulability in these patients.
Methods We analyzed the HIV patients who followed up with our Vascular Medicine outpatient clinic with venous thromboembolism (VTE) over the past 3 years and followed them prospectively. The patients included were those who had minimum, regular follow-up of 3 months, with a Doppler scan in the beginning and last follow-up. Patients were analyzed for age, gender, race, site of thrombosis, coagulation factors, lipid panel, type of antiretroviral treatment, past or present history of infections or malignancy, CD4 absolute and helper cell counts at the beginning of thrombosis, response to treatment and outcome. Patients with HIV with arterial thrombosis were excluded.
Results A total of eight patients were analyzed. The mean age was 49.87 years (range, 38-58 years). All were male patients with six patients having lower limb thrombosis, one patient with upper limb thrombosis related to peripheral inserted central catheter (PICC), and one patient had pulmonary embolism with no deep vein thrombosis. Most common venous thrombosis was popliteal vein thrombosis, followed by common femoral, superficial femoral and external iliac thrombosis. Two patients had deficiency of protein S, two had high homocysteine levels, one had deficiency of antithrombin 3, and one had increase in anticardiolipin Immunoglobulin antibody. All patients were taking nucleoside and nonnucleoside inhibitors but only two patients were taking protease inhibitors. There was history of lymphoma in one and nonsmall cell lung carcinoma in one patient. Three patients had past history of tuberculosis and one of these patients also had pneumocystis carinii pneumonia. The mean absolute CD4 counts were 383.25 cells/UL (range, 103-908 cells/UL) and helper CD4 counts were 22.5 cells/UL (range, 12-45 cells/UL). All were anticoagulated with warfarin or enoxaparin. There was complete resolution of deep vein thrombosis in two patients (one with PICC line thrombosis in 3 months and other with popliteal vein thrombosis in 1 year). There was extension of clot in one patient and no resolution in others. Seven patients are still alive and on regular follow-up.
Conclusion Thrombosis in HIV patients is seen more commonly in middle aged, community ambulant male patients. Left lower limb involvement with involvement of popliteal vein is most common. Deficiency of protein S and hyperhomocystenaemia were noted in these patients. Most of these patients did not respond to therapeutic anticoagulation, but the extension of the thrombosis was prevented in majority of cases.
doi:10.1055/s-0033-1333866
PMCID: PMC3709953  PMID: 24436591
anticoagulation; protein C; protein S; homocysteine; antithrombin 3; duplex; enoxaparin; risk factors
10.  Inflammatory Cytokines as Risk Factors for a First Venous Thrombosis: A Prospective Population-Based Study 
PLoS Medicine  2006;3(8):e334.
Background
In case-control studies, elevated levels of interleukins 6 and 8 have been found to be associated with an increased risk of venous thrombosis (VT). Because of the design of these studies, it remained uncertain whether these alterations were a cause or a result of the VT. In order to distinguish between the two, we set out to measure the levels of six inflammatory markers prior to thrombosis in a population-based cohort using a nested case-cohort design.
Methods and Findings
Between August 1995 and June 1997, blood was collected from 66,140 people in the second Norwegian Health Study of Nord-Trøndelag (HUNT2). We identified venous thrombotic events occurring between entry and 1 January 2002. By this date we had registered 506 cases with a first VT; an age- and sex-stratified random sample of 1,464 controls without previous VT was drawn from the original cohort. Levels of interleukins 1β, 6, 8, 10, 12p70, and tumour necrosis factor-α were measured in the baseline sample that was taken 2 d to 75 mo before the event (median 33 mo). Cut-off points for levels were the 80th, 90th, and 95th percentile in the control group. With odds ratios ranging from 0.9 (95% CI: 0.6–1.5) to 1.1 (95% CI: 0.7–1.8), we did not find evidence for a relationship between VT and an altered inflammatory profile.
Conclusions
The results from this population sample show that an altered inflammatory profile is more likely to be a result rather than a cause of VT, although short-term effects of transiently elevated levels cannot be ruled out.
An altered inflammatory profile appears more likely to be a result than a cause of venous thrombosis.
Editors' Summary
Background.
Blood clots (thromboses) are a common medical problem, especially in people who have been immobilized for a variety of reasons, who have other medical or surgical conditions, or who take certain types of drugs such as oral contraceptives. As well as these factors, various genetic changes make it more likely that certain people will develop a thrombosis. The most well known of these genetic changes is in a clotting factor, Factor V. Instead of the normal clotting factor V, some people have a variant known as Factor V Leiden, which makes them more likely to develop a thrombosis. (It is so named as it was discovered by researchers in Leiden, Netherlands.) Researchers are trying to find out if other abnormalities, particularly in levels of substances involved in inflammation, might make the chance of thrombosis more common. Identifying such changes might make it easier to predict who might be at risk of getting a thrombosis—for example, when a patient has to have an operation—and thus give them appropriate preventative measures.
Why Was This Study Done?
Previous studies have shown that the levels of inflammatory substances, known as cytokines, are raised around the time of a thrombosis. However, because of the design of these studies it was not clear whether these alterations were a cause or a result of the thrombosis. These researchers wanted to measure the levels of six cytokines before thrombosis in a large group of people and follow them to see if any particular level of cytokine made it more likely that they would go on to develop a thrombosis.
What Did the Researchers Do and Find?
During a three-year period between August 1995 and June 1997, blood was collected from 66,140 people in the second Norwegian Health Study of Nord-Trøndelag (HUNT2). Anyone who had a thrombosis between the start of the study and the beginning of 2002 was identified—506 people in all. Blood samples, taken from these people (cases) between two days and 75 months before the thrombosis happened, were used to measure levels of a number of different cytokines (abbreviated to IL-1β, IL-6, IL-8, IL-10, IL12p70, and tumour necrosis factor alpha [TNF-α]). These levels were then compared with those in samples also taken earlier from 1,464 people who were similar to the cases but had no thrombosis (controls). The authors found no evidence for a relationship between the chance of getting a thrombosis and a change in any of these markers of inflammation.
What Do These Findings Mean?
It seems unlikely that any long-term changes in levels of cytokines make any difference as to whether or not people develop a thrombosis. Hence, any changes seen in previous studies are most likely to have been the result of the thrombosis. However, the researchers could not rule out that changes occurred in the hours or days immediately before the thrombosis, although that seems unlikely. In any case, the levels of these cytokines do not seem to be useful as a clinical tool to predict who is at risk of thrombosis.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/101371/journal.pmed.0030334.
MedlinePlus encyclopedia entries on deep venous thrombosis and pulmonary embolus
Omni, a health information service in the UK run by the Resource Discovery Network, has links to pages of information on venous thrombosis
The HUNT studies are described in this Web site
doi:10.1371/journal.pmed.0030334
PMCID: PMC1551920  PMID: 16933968
11.  Is there a Link Between Atherothrombosis and Deep Venous Thrombosis? 
Mædica  2014;9(1):94-97.
Venous and arterial thromboses have traditionnally been regarded as separate diseases with different causes. Clinical experience shows, that the arterial atherothrombotic disease can be associated with venous thrombotic disease, but there is insufficient evidence to prove and explain the nature of this association.
This review focuses on the risk factors associated with both arterial and venous thrombotic events, and recent epidemiological studies have documented an association between these vascular complications.
According to the results of recent studies, atherosclerosis and venous thrombosis share common risk factors, including age, obesity, cigarette smoking, and metabolic syndrome.
Several studies have demonstrated that subjects with idiopathic venous thrombosis have an increased risk of cardiovascular events compared with subjects with secondary thrombosis or control group. On the other hand, atherosclerosis has the potential to promote the development of thrombotic disorders in the venous system. Based on the results of population studies carried out in the United States, atherosclerosis is unlikely to constitute a risk factor for venous thrombosis. In conclusion, the separate nature of arterial and venous disorders has been challenged. Future studies are needed to clarify the nature of this association, and to evaluate its implications for clinical practice.
PMCID: PMC4268301  PMID: 25553135
atherosclerosis; deep venous thrombosis; risk factor; prospective study
12.  Platelet Activation and Anti-Phospholipid Antibodies Collaborate in the Activation of the Complement System on Platelets in Systemic Lupus Erythematosus 
PLoS ONE  2014;9(6):e99386.
Anti-phospholipid (aPL) antibodies are important contributors to development of thrombosis in patients with the autoimmune rheumatic disease systemic lupus erythematosus (SLE). The underlying mechanism of aPL antibody-mediated thrombosis is not fully understood but existing data suggest that platelets and the complement system are key components. Complement activation on platelets is seen in SLE patients, especially in patients with aPL antibodies, and has been related to venous thrombosis and stroke. The aim of this study was to investigate if aPL antibodies could support classical pathway activation on platelets in vitro as well as in SLE patients. Furthermore, we investigated if complement deposition on platelets was associated with vascular events, either arterial or venous, when the data had been adjusted for traditional cardiovascular risk factors. Finally, we analyzed if platelet complement deposition, both C1q and C4d, was specific for SLE. We found that aPL antibodies supported C4d deposition on platelets in vitro as well as in SLE patients (p = 0.001 and p<0.05, respectively). Complement deposition on platelets was increased in SLE patients when compared with healthy individuals (p<0.0001). However, high levels of C4d deposition and a pronounced C1q deposition were also seen in patients with rheumatoid arthritis and systemic sclerosis. In SLE, C4d deposition on platelets was associated with platelet activation, complement consumption, disease activity and venous (OR = 5.3, p = 0.02), but not arterial, thrombosis, observations which were independent of traditional cardiovascular risk factors. In conclusion, several mechanisms operate in SLE to amplify platelet complement deposition, of which aPL antibodies and platelet activation were identified as important contributors in this investigation. Complement deposition on platelets was identified as a marker of venous, but not arterial thrombosis, in SLE patients independently of traditional risk factors and aPL antibodies. Further studies are needed to elucidate the role of complement deposition on platelets in development of venous thrombosis.
doi:10.1371/journal.pone.0099386
PMCID: PMC4055750  PMID: 24922069
13.  Effect of Statins on Venous Thromboembolic Events: A Meta-analysis of Published and Unpublished Evidence from Randomised Controlled Trials 
PLoS Medicine  2012;9(9):e1001310.
A systematic review and meta-analysis conducted by Kazem Rahimi and colleagues re-evaluates the hypothesis, generated in previous studies, that statins may reduce the risk of venous thromboembolic events. Their meta-analysis does not support the previous findings.
Background
It has been suggested that statins substantially reduce the risk of venous thromboembolic events. We sought to test this hypothesis by performing a meta-analysis of both published and unpublished results from randomised trials of statins.
Methods and Findings
We searched MEDLINE, EMBASE, and Cochrane CENTRAL up to March 2012 for randomised controlled trials comparing statin with no statin, or comparing high dose versus standard dose statin, with 100 or more randomised participants and at least 6 months' follow-up. Investigators were contacted for unpublished information about venous thromboembolic events during follow-up. Twenty-two trials of statin versus control (105,759 participants) and seven trials of an intensive versus a standard dose statin regimen (40,594 participants) were included. In trials of statin versus control, allocation to statin therapy did not significantly reduce the risk of venous thromboembolic events (465 [0.9%] statin versus 521 [1.0%] control, odds ratio [OR] = 0.89, 95% CI 0.78–1.01, p = 0.08) with no evidence of heterogeneity between effects on deep vein thrombosis (266 versus 311, OR 0.85, 95% CI 0.72–1.01) and effects on pulmonary embolism (205 versus 222, OR 0.92, 95% CI 0.76–1.12). Exclusion of the trial result that provided the motivation for our meta-analysis (JUPITER) had little impact on the findings for venous thromboembolic events (431 [0.9%] versus 461 [1.0%], OR = 0.93 [95% CI 0.82–1.07], p = 0.32 among the other 21 trials). There was no evidence that higher dose statin therapy reduced the risk of venous thromboembolic events compared with standard dose statin therapy (198 [1.0%] versus 202 [1.0%], OR = 0.98, 95% CI 0.80–1.20, p = 0.87). Risk of bias overall was small but a certain degree of effect underestimation due to random error cannot be ruled out.
Please see later in the article for the Editors' Summary.
Conclusions
The findings from this meta-analysis do not support the previous suggestion of a large protective effect of statins (or higher dose statins) on venous thromboembolic events. However, a more moderate reduction in risk up to about one-fifth cannot be ruled out.
Editors' Summary
Background
Blood normally flows smoothly throughout the human body, supplying its organs and tissues with oxygen and nutrients. But, when an injury occurs, proteins called clotting factors make the blood gel (coagulate) at the injury site. The resultant blood clot (thrombus) plugs the wound and prevents blood loss. Occasionally, however, a thrombus forms inside an uninjured blood vessel and partly or completely blocks the blood flow. A clot inside one of the veins (vessels that take blood towards the heart) deep within the body is called a deep vein thrombosis (DVT). Symptoms of DVT (which usually occurs in the leg) include pain, swelling, and redness in the affected limb. DVT is treated with heparin and warfarin, two anticoagulant drugs that stop the blood clot growing. If left untreated, part of the clot (an embolus) can break off and travel to the lungs, where it can cause a pulmonary embolism (PE), a life-threatening condition characterized by chest pain, breathlessness, coughing, and dizziness. Little is known about how to prevent DVTs and PEs but risk factors for these venous thromboembolic events include having an inherited blood clotting disorder, oral contraceptive use, having surgery, and prolonged inactivity (on long-haul plane flights, for example).
Why Was This Study Done?
In 2009, a secondary (add-on) analysis of data from a randomized controlled trial (RCT, a study that randomly assigns individuals to receive different treatments and compares the outcomes associated with each treatment) called the JUPITER trial reported that rosuvastatin—a cholesterol-lowering drug (statin)—halved the risk of venous thromboembolic events among apparently healthy adults. The JUPITER trial was initiated to test whether statins reduce the risk of strokes, heart attacks, and other cardiovascular diseases (conditions that involve the heart and the blood vessels) among adults with raised levels of a predictor for these diseases called C-reactive protein; statins reduce the levels of this protein as well as those of cholesterol. Because fewer than 100 of the participants in the JUPITER trial developed a DVT or PE, the reduction in the risk of a venous thromboembolic event among the participants who took rosuvastatin could have happened by chance. In this systematic review and meta-analysis of 29 RCTs of statins that collected information on many more venous thromboembolic events, the researchers test the hypothesis that statins substantially reduce the risk of such events. A systematic review uses predefined criteria to identify all the research on a given topic; a meta-analysis is a statistical approach that combines the results of several studies.
What Did the Researchers Do and Find?
The researchers identified 22 RCTs (105,759 participants) that compared the effects of statins with control (dummy) tablets and seven (40,594 participants) that compared an intensive statin regimen with a standard regimen. They then obtained largely unpublished information about the venous thromboembolic events that occurred during these trials (about 1,000 DVTs and PEs) from the original investigators. In the trials of statin versus control, allocation to statin therapy did not significantly reduce the risk of venous thromboembolic events. Thus, although events occurred in 465 participants who were given statins (0.9% of the participants) and in 521 participants who were given control tablets (1% of the participants), this difference in outcomes was not statistically significant—it could have happened by chance. Exclusion of the JUPITER trial results from the meta-analysis did not alter this finding. The researchers also found no evidence that intensive statin therapy reduced the risk of venous thromboembolic events compared to standard therapy.
What Do These Findings Mean?
The findings of this meta-analysis do not support the suggestion that statins, either at the standard dose or at higher doses, reduce the risk of venous thromboembolic events substantially among healthy adults. It is possible that the effect of statins has been underestimated in this meta-analysis because of missing data or because of some other source of bias. Furthermore, because the total number of events in this meta-analysis is still relatively modest, these findings do not rule out the possibility that statins may reduce the risk of venous thromboembolic events by up to about one-fifth in some or all individuals. Additional large RCTs are now needed to investigate whether statin treatment does in fact reduce the risk of venous thromboembolic events in adults and, if it does, whether all statins have a similar effect and whether statin treatment is beneficial in everyone or only in specific subgroups of people.
Additional Information
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001310.
This study is further discussed in a PLOS Medicine Perspective by Frits Rosendaal
The US National Heart Lung and Blood Institute provides information on deep vein thrombosis (including an animation about how DVT causes pulmonary embolisms), and information on pulmonary embolism
The UK National Health Service Choices website has information on deep vein thrombosis, including personal stories, on pulmonary embolism, and on statins; a Behind the Headlines article describes the JUPITER trial and its implications
The non-profit organization US National Blood Clot Alliance provides detailed information about deep vein thrombosis and pulmonary embolism for patients and professionals and includes a selection of personal stories about these conditions
MedlinePlus has links to further information about deep vein thrombosis, pulmonary embolism, and statins (in English and Spanish)
doi:10.1371/journal.pmed.1001310
PMCID: PMC3445446  PMID: 23028261
14.  Higher risk of venous thrombosis associated with drospirenone-containing oral contraceptives: a population-based cohort study 
Background:
Combined oral contraceptives are a common method of contraception, but they carry a risk of venous and arterial thrombosis. We assessed whether use of drospirenone was associated with an increase in thrombotic risk relative to third-generation combined oral contraceptives.
Methods:
Using computerized records of the largest health care provider in Israel, we identified all women aged 12 to 50 years for whom combined oral contraceptives had been dispensed between Jan. 1, 2002, and Dec. 31, 2008. We followed the cohort until 2009. We used Poisson regression models to estimate the crude and adjusted rate ratios for risk factors for venous thrombotic events (specifically deep vein thrombosis and pulmonary embolism) and arterial thromboic events (specifically transient ischemic attack and cerebrovascular accident). We performed multivariable analyses to compare types of contraceptives, with adjustment for the various risk factors.
Results:
We identified a total of 1017 (0.24%) venous and arterial thrombotic events among 431 223 use episodes during 819 749 woman-years of follow-up (6.33 venous events and 6.10 arterial events per 10 000 woman-years). In a multivariable model, use of drospirenone carried an increased risk of venous thrombotic events, relative to both third-generation combined oral contraceptives (rate ratio [RR] 1.43, 95% confidence interval [CI] 1.15–1.78) and second-generation combined oral contraceptives (RR 1.65, 95% CI 1.02–2.65). There was no increase in the risk of arterial thrombosis with drospirenone.
Interpretation:
Use of drospirenone-containing oral contraceptives was associated with an increased risk of deep vein thrombosis and pulmonary embolism, but not transient ischemic attack or cerebrovascular attack, relative to second- and third-generation combined oral contraceptives.
doi:10.1503/cmaj.110463
PMCID: PMC3255137  PMID: 22065352
15.  Elevated prothrombin promotes venous, but not arterial, thrombosis in mice 
Objective
Individuals with elevated prothrombin, including those with the prothrombin G20210A mutation, have increased risk of venous thrombosis. Although these individuals do not have increased circulating prothrombotic biomarkers, their plasma demonstrates increased tissue factor-dependent thrombin generation in vitro. The objectives of this study were to determine the pathologic role of elevated prothrombin in venous and arterial thrombosis in vivo, and distinguish thrombogenic mechanisms in these vessels.
Approach and results
Prothrombin was infused into mice to raise circulating levels. Venous thrombosis was induced by electrolytic stimulus to the femoral vein or inferior vena cava ligation. Arterial thrombosis was induced by electrolytic stimulus or ferric chloride application to the carotid artery. Mice infused with prothrombin demonstrated increased tissue factor-triggered thrombin generation measured ex vivo, but did not have increased circulating prothrombotic biomarkers in the absence of vessel injury. Following venous injury, elevated prothrombin increased thrombin generation and the fibrin accumulation rate and total amount of fibrin ~3-fold, producing extended thrombi with increased mass. However, elevated prothrombin did not accelerate platelet accumulation, increase the fibrin accumulation rate, or shorten the vessel occlusion time following arterial injury.
Conclusions
These findings reconcile previously discordant findings regarding thrombin generation in hyperprothrombinemic individuals measured ex vivo and in vitro, and show elevated prothrombin promotes venous, but not arterial, thrombosis in vivo.
doi:10.1161/ATVBAHA.113.301607
PMCID: PMC3779620  PMID: 23723374
16.  Factor V Leiden Is Associated with Higher Risk of Deep Venous Thrombosis of Large Blood Vessels 
Croatian medical journal  2006;47(3):433-439.
Aim
To determine the prevalence of factor V Leiden mutation in patients with different presentation of venous thromboembolic disease and healthy individuals in the Republic of Macedonia.
Methods
The retrospective case-control study involved 190 patients with venous thromboembolic disease and 200 healthy individuals, who were screened for the presence of factor V Leiden mutation, using a polymerase chain reaction-restriction fragment length polymorphism method. The prevalence of factor V Leiden was analyzed according to the localization of thrombosis, presence of risk factors, and family history of thrombosis. The odds of deep venous thrombosis were calculated with respect to the presence of factor V Leiden mutation.
Results
The prevalence of factor V Leiden mutation among patients with venous thromboembolic disease was 21.1%, compared with 5.5% in the healthy individuals. Factor V Leiden positive patients had the first episode of deep venous thrombosis at a younger age, and the prevalence of the mutation was the highest among patients with a positive family history of thrombosis (33.9%, P = 0.003) and in patients with deep venous thrombosis affecting a large blood vessel (37.7%, P = 0.001). The prevalence of factor V Leiden mutation was lower in patients with calf deep venous thrombosis and primary thromboembolism (13.3% and 13.1%, respectively; P>0.05). The odds ratio for iliofemoral or femoral deep venous thrombosis in factor V Leiden carriers was 10.4 (95% confidence interval, 4.7-23.1).
Conclusion
The prevalence of factor V Leiden mutation was high in patients with venous thromboembolic disease and healthy individuals in the Republic of Macedonia. Factor V Leiden carriers have the highest odds of developing deep venous thrombosis affecting a large venous blood vessel.
PMCID: PMC2080416  PMID: 16758522
17.  Idiopathic venous thromboembolism and thrombophilia  
Journal of Medicine and Life  2011;4(1):57-62.
During the past decade idiopathic venous thromboembolism has become a separate entity, a chronic illness which has required prolonged anticoagulation and other prevention strategies to avoid recurrences. This article reviews recent developments regarding unprovoked venous thromboembolism and its relation with thrombophilia. In the beginning, the latest definition of idiopathic venous thromboembolism is presented. The article continues with statistics about thrombophilia, related venous thromboembolism, and a classification of major thrombophilic factors according to their intrinsic risk of thrombosis and of thrombotic recurrences. Great interest is given to the predictors of recurrence and the importance of prolonged anticoagulation is underlined. The antiphospholipid antibody syndrome, the most common acquired thrombophilia, is presented separately. The revised diagnosis criteria are discussed. Some characteristics of the antiphospholipid syndrome are worth presenting: the risk of both venous and arterial thrombosis, the high risk of thrombotic recurrence and the diversity of antiphospholipid antibodies.
Patients experiencing idiopathic venous thromboembolic event have a great risk of recurrence, and highly benefit from long time anticoagulation. Natural coagulation inhibitors deficiencies, homozygous factor V Leiden and prothrombin G20210A and the antiphospholipid syndrome, increase the risk of first venous thrombosis and their recurrences and require adequate prevention.
Abbreviations: VTE–venous thromboembolism, HRT–hormone replacement therapy, AVK–antivitamin K, FVL–factor V Leiden, PT G20210A–prothrombin G20210A, TAFI–thrombin activatable fibrinolysis inhibitor, PAI–1–plasminogen activator inhibitor 1, T–PA–tissue plasminogen activator, APS–antiphospholipid syndrome, LA–lupus anticoagulant, Abeta2GP1–anti beta2 glycoprotein 1.
PMCID: PMC3056423  PMID: 21505575
thromboembolism; hypercoagulability; antiphospholipid syndrome; recurrence
18.  Risk factors and recurrent thrombotic episodes in patients with cerebral venous thrombosis 
Blood Transfusion  2014;12(Suppl 1):s337-s342.
Background
The prevalence of thrombophilic abnormalities in patients with cerebral vein thrombosis has been reported to be similar to that in patients with deep vein thrombosis of the lower limb. The role of gender-specific risk factors (pregnancy, oral contraceptives) is well established, whereas that of other acquired risk conditions is debated.
Materials and methods
We screened 56 patients with cerebral vein thrombosis and 184 age- and sex-matched apparently healthy controls for prothrombin (factor II, FII) G20210A and factor V Leiden polymorphisms; protein S, protein C, and antithrombin deficiency; anticardiolipin antibodies; hyperhomocysteinaemia and other putative risk factors.
Results
The G20210A polymorphism was found in 29.1% of patients and in 5.7% of controls (odds ratio [OR] 7.1; P <0.0001; adjusted OR 12.67, P <0.0001). Frequencies of factor V Leiden and hyperhomocysteinaemia were not significantly different in patients and controls, nor were the other thrombophilic tests and some established cardiovascular risk factors, such as smoking, obesity or overweight and arterial hypertension. Conversely, 53.7% of the women who developed cerebral vein thrombosis did so while assuming oral contraceptives (OR 6.12; P <0.0001), with a further increase of risk in FII G20210A carriers (OR 48.533). Some associated diseases (onco-haematological disorders and infections) also had a significant role. Over a median 7-year follow-up, irrespective of the duration of antithrombotic treatment, 9/56 (16%) patients had further episodes of venous/arterial thrombosis. No significant risk factor for recurrent thrombosis was identified.
Discussion
In spite of the limitations of the sample size, our data confirm the role of FII G20210A mutation in this setting and its interactions with acquired risk factors such as oral contraceptives, also highlighting the risk of recurrent thrombosis in cerebral vein thrombosis patients.
doi:10.2450/2013.0196-12
PMCID: PMC3934282  PMID: 23399370
risk factors; cerebral venous thrombosis; recurrences
19.  The Absolute Risk of Venous Thrombosis after Air Travel: A Cohort Study of 8,755 Employees of International Organisations 
PLoS Medicine  2007;4(9):e290.
Background
The risk of venous thrombosis is approximately 2- to 4-fold increased after air travel, but the absolute risk is unknown. The objective of this study was to assess the absolute risk of venous thrombosis after air travel.
Methods and Findings
We conducted a cohort study among employees of large international companies and organisations, who were followed between 1 January 2000 and 31 December 2005. The occurrence of symptomatic venous thrombosis was linked to exposure to air travel, as assessed by travel records provided by the companies and organisations. A long-haul flight was defined as a flight of at least 4 h and participants were considered exposed for a postflight period of 8 wk. A total of 8,755 employees were followed during a total follow-up time of 38,910 person-years (PY). The total time employees were exposed to a long-haul flight was 6,872 PY. In the follow-up period, 53 thromboses occurred, 22 of which within 8 wk of a long-haul flight, yielding an incidence rate of 3.2/1,000 PY, as compared to 1.0/1,000 PY in individuals not exposed to air travel (incidence rate ratio 3.2, 95% confidence interval 1.8–5.6). This rate was equivalent to a risk of one event per 4,656 long-haul flights. The risk increased with exposure to more flights within a short time frame and with increasing duration of flights. The incidence was highest in the first 2 wk after travel and gradually decreased to baseline after 8 wk. The risk was particularly high in employees under age 30 y, women who used oral contraceptives, and individuals who were particularly short, tall, or overweight.
Conclusions
The risk of symptomatic venous thrombosis after air travel is moderately increased on average, and rises with increasing exposure and in high-risk groups.
In a cohort study of 8,755 employees of large international organizations followed for 38,910 person-years, Suzanne Cannegieter and colleagues find a risk of one thrombosis per 4,656 long-haul flights.
Editors' Summary
Background.
Blood normally flows smoothly throughout the human body, supplying the brain and other vital organs with oxygen and nutrients. When an injury occurs, proteins called clotting factors make the blood gel or coagulate at the injury site. The resultant blood clot (thrombus) plugs the wound and prevents blood loss. Sometimes, however, a thrombus forms inside an uninjured blood vessel and partly or completely blocks the blood flow. A clot inside one of the veins (vessels that take blood to the heart) deep within the body is called a deep vein thrombosis (DVT). Symptoms of DVT (which usually occurs in the deep veins of the leg) include pain, swelling, and redness in one leg. DVT is usually treated with heparin and warfarin, two anticoagulant drugs that stop the blood clot growing. If left untreated, part of the clot (an embolus) can break off and travel to the lungs, where it can cause a life-threatening condition called pulmonary embolism (PE). Fortunately, DVT and PE are rare but having an inherited blood clotting disorder, taking an oral contraceptive, and some types of surgery are all risk factors for them. In addition, long-haul plane travel increases the risk of DVT and PE, known collectively as venous thrombosis (VT) 2- to 4-fold, in part because the enforced immobilization during flights slows down blood flow.
Why Was This Study Done?
Although the link between air travel and VT was first noticed in the 1950s, exactly how many people will develop DVT and PE (the absolute risk of developing VT) after a long flight remains unknown. This information is needed so that travelers can be given advice about their actual risk and can make informed decisions about trying to reduce that risk by, for example, taking small doses of anticoagulant medicine before a flight. In this study, the researchers have determined the absolute risk of VT during and after long-haul air travel in a large group of business travelers.
What Did the Researchers Do and Find?
The researchers enrolled almost 9,000 employees from several international companies and organizations and followed them for an average of 4.4 years. The details of flights taken by each employee were obtained from company records, and employees completed a Web-based questionnaire about whether they had developed VT and what risk factors they had for the condition. Out of 53 thrombi that occurred during the study, 22 occurred within eight weeks of a long-haul flight (a flight of more than four hours). From this and data on the total time employees spent on long-haul flights, the researchers calculated that these flights tripled the risk of developing VT, and that the absolute risk (the probability of something occurring in a certain time period) of a VT occurring shortly after such travel was one event per 4,656 flights. They also calculated that the risk of VT was increased by exposure to more flights during a short period and to longer flights and was greatest in the first two weeks after a flight. In addition, the risk of VT was particularly high in young employees, women taking oral contraceptives, and people who were short, tall or overweight.
What Do These Findings Mean?
The main finding of this study is that the absolute risk of VT after of a long-haul flight is low—only one passenger out of nearly 5,000 is likely to develop VT because of flying. However, the study included only healthy people without previous VT whose average age was 40 years, so the absolute risk of VT after long-haul flights might be higher in the general traveling population. Even so, this finding strongly suggests that prophylactic (preventative) use of anticoagulants by all long-haul travelers may not be justified because these drugs have potentially dangerous side effects (for example, they can cause uncontrolled bleeding). Subgroups of travelers with additional risk factors for VT might, however, benefit from the use of this and other prophylactic measures, but randomized trials are needed to find out who would benefit most from which prophylactic measure.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040290.
MedlinePlus encyclopedia pages on blood clots, deep vein thrombosis, and pulmonary embolism (in English and Spanish)
Information from the US National Heart Lung and Blood Institute on deep vein thrombosis, including an animation of how DVT causes pulmonary embolisms
Information for patients from the UK National Health Service Direct health encyclopedia on deep vein thrombosis (in several languages)
Information for travelers on DVT from the US Centers for Disease Control and Prevention and from the UK National Travel Health Network and Centre
This study came out of the WHO Research Into Global Hazards of Travel (WRIGHT) project, and WHO's WRIGHT project on Air Travel and Venous Thromboembolism, of which his study forms a part, has a Web site
doi:10.1371/journal.pmed.0040290
PMCID: PMC1989755  PMID: 17896862
20.  Risk Factors and Underlying Mechanisms for Venous Stasis Syndrome: A Population-Based Case-Control Study 
Background
Venous stasis syndrome may complicate deep vein thrombosis (DVT; i.e., post-phlebitic syndrome), but in most cases, venous stasis syndrome is not post-phlebitic.
Objective
To determine risk factors (including prior DVT) for venous stasis syndrome, and to assess venous outflow obstruction and venous valvular incompetence as possible mechanisms for venous stasis syndrome.
Design
Case-control study nested within a population-based inception cohort.
Population
232 Olmsted County, MN residents with a first lifetime venous thromboembolism (VTE), and 133 residents without VTE.
Measurements
Questionnaire and physical examination for venous stasis syndrome; strain gauge outflow plethysmography, venous continuous wave Doppler ultrasonography and passive venous drainage and refill testing for venous outflow obstruction and venous valvular incompetence.
Results
Altogether, 161 (44%), 43 (12%), and 136 (38%) subjects respectively, had venous stasis syndrome, venous outflow obstruction and venous valvular incompetence. Independent risk factors for venous stasis syndrome included increasing patient age and body mass index (BMI), prior DVT, longer time interval since DVT, and varicose veins. Both venous outflow obstruction (p=0.003) and venous valvular incompetence (p<0.0001) were strongly associated with venous stasis syndrome. Increasing age and prior DVT were significantly associated with venous outflow obstruction, while prior DVT, varicose veins and venous stasis syndrome diagnosed prior to the incident DVT were significantly associated with venous valvular incompetence. The risks of venous outflow obstruction, venous valvular incompetence and venous stasis syndrome were higher with left leg DVT.
Conclusions
Increasing patient age and BMI, prior DVT (particularly left leg DVT), longer time interval since DVT and varicose veins are independent risk factors for venous stasis syndrome. Venous stasis syndrome related to DVT is due to venous outflow obstruction and venous valvular incompetence, while venous stasis syndrome related to older age and to varicose veins is due to venous outflow obstruction and to venous valvular incompetence, respectively.
doi:10.1177/1358863X09104222
PMCID: PMC2990921  PMID: 19808719
Deep Vein Thrombosis; Venous Thromboembolism; Venous Stasis Syndrome; Post Thrombotic Syndrome; Risk Factors; Epidemiology
21.  Elevated Heparin-Induced Antibodies Are More Common in Diabetic Patients with Vascular Disease 
Thrombosis  2014;2014:649652.
Background. Hypercoagulable disorders can lead to deep vein thrombosis (DVT), arterial thrombosis or embolization, and early or recurrent bypass graft failure. The purpose of this study was to identify whether diabetes increased the likelihood of heparin-induced platelet factor 4 antibodies in at risk vascular patients. Methods. We reviewed clinical data on 300 consecutive patients. A hypercoagulable workup was performed if patients presented with (1) early bypass/graft thrombosis (<30 days), (2) multiple bypass/graft thrombosis, and (3) a history of DVT, pulmonary embolus (PE), or native vessel thrombosis. Relevant clinical variables were analyzed and compared between patients with diabetes (DM) and without diabetes (nDM). Results. 85 patients (47 women; age 53 ± 16 years, range 16–82 years) had one of the defined conditions and underwent a hypercoagulable evaluation. Screening was done in 4.7% of patients with early bypass graft thrombosis, 60% of patients were screened because of multiple bypass or graft thrombosis, and 35.3% had a previous history of DVT, PE, or native vessel thrombosis. Of the 43 patients with DM and 42 nDM evaluated, 59 patients (69%) had an abnormal hypercoagulable profile. An elevated heparin antibody level was present in 30% of DM and 12% of nDM patients (chi-squared test P < 0.04). Additionally, DM was associated with a higher likelihood of arterial complications while nDM was associated with a higher rate of venous adverse events (chi-squared test P < 0.003). Conclusions. Diabetes is associated with a higher likelihood of developing heparin-induced antibodies and an increased combined incidence of arterial complications that include early or multiple bypass/graft thrombosis. This finding may influence the choice of anticoagulation in diabetic patients at risk with vascular disease.
doi:10.1155/2014/649652
PMCID: PMC3941208  PMID: 24672719
22.  Risk factors for venous thrombosis associated with peripherally inserted central venous catheters 
To evaluate the risk factors associated with an increased risk of symptomatic peripherally inserted central venous catheter (PICC)-related venous thrombosis. Retrospective analyses identified 2313 patients who received PICCs from 1 January 2012 to 31 December 2013. All 11 patients with symptomatic PICC-related venous thrombosis (thrombosis group) and 148 who did not have thromboses (non-thrombosis group) were selected randomly. The medical information of 159 patients (age, body mass index (BMI), diagnosis, smoking history, nutritional risk score, platelet count, leucocyte count as well as levels of D-dimer, fibrinogen, and degradation products of fibrin) were collected. Logistic regression analysis was undertaken to determine the risk factors for thrombosis. Of 2313 patients, 11 (0.47%) were found to have symptomatic PICC-related venous thrombosis by color Doppler ultrasound. Being bedridden for a long time (odds ratio [(OR]), 17.774; P=0.0017), D-dimer >5 mg/L (36.651; 0.0025) and suffering from one comorbidity (8.39; 0.0265) or more comorbidities (13.705; 0.0083) were the major risk factors for PICC-catheter related venous thrombosis by stepwise logistic regression analysis. Among 159 patients, the prevalence of PICC-associated venous thrombosis in those with ≥1 risk factor was 10.34% (12/116), in those with ≥2 risk factors was 20.41% (10/49), and in those with >3 risk factors was 26.67% (4/15). Being bedridden >72 h, having increased levels of D-dimer (>5 mg/L) and suffering from comorbidities were independent risk factors of PICC-related venous thrombosis.
PMCID: PMC4307559  PMID: 25664112
Peripherally inserted central catheter; thrombosis; risk factors
23.  Identification of Risk Factors for Vascular Thrombosis May Reduce Early Renal Graft Loss: A Review of Recent Literature 
Journal of Transplantation  2012;2012:793461.
Renal graft survival has improved over the past years, mainly owing to better immunosuppression. Vascular thrombosis, though rare, therefore accounts for up to one third of early graft loss. We assess current literature on transplantation, identify thrombosis risk factors, and discuss means of avoiding thrombotic events and saving thrombosed grafts. The incidence of arterial thrombosis was reported to 0.2–7.5% and venous thrombosis 0.1–8.2%, with the highest incidence among children and infants, and the lowest in living donor reports. The most significant risk factors for developing thrombosis were donor-age below 6 or above 60 years, or recipient-age below 5-6 years, per- or postoperative hemodynamic instability, peritoneal dialysis, diabetic nephropathy, a history of thrombosis, deceased donor, or >24 hours cold ischemia. Multiple arteries were not a risk factor, and a right kidney graft was most often reported not to be. Given the thrombosed kidney graft is diagnosed in time, salvage is possible by urgent reoperation and thrombectomy. Despite meticulous attentions to reduce thrombotic risk factors, thrombosis cannot be entirely prevented and means to an early detection of this complication is desirable in order to save the kidneys through prompt reoperation. Microdialysis may be a new tool for this.
doi:10.1155/2012/793461
PMCID: PMC3369524  PMID: 22701162
24.  An unusual cause of acute abdominal pain – A case presentation 
Background
In 1983, Graham Hughes described a condition of Antiphospholipid Syndrome in which there was a danger of thrombosis. The condition is readily detectable by blood tests and, once diagnosed; the risk of further thrombosis can be significantly reduced by anticoagulation treatments. Affected groups of patients can be distinguished by a specific blood test – the detection of antiphospholipid antibody (Ref-1). Patients with Hughes syndrome have hypercoaguable state with a markedly increased risk of both arterial and venous thrombosis and there is temporal persistence of antibody positivity.
Case presentation
A 44-year-old woman was admitted under the acute surgical "take" with left sided abdominal pain radiating to her back. She had a history of borderline thyrotoxicosis in the early 1990s. She was on etonogestrel-releasing implants for contraception and there was no history of previous deep venous thrombosis. She was very tender, locally, over the left side of the abdomen. Investigations showed haemoglobin of 13.2 g/dl, white cell count of 19.9 10*9/L, and platelets 214 10*9/L with neutrophilia. Amylase and renal function tests were found to be normal. Liver function tests were deranged with Gamma GT 244 u/l (twice normal). An abdominal Ultrasound Scan suggested a possible splenic infarction, which was confirmed by a CT scan of her abdomen. Tests were carried out to investigate the possibility of a post thrombotic state. Coagulation risk factors for thrombosis were within the normal limits; Protein S 67 %(60–140), Protein C 103 % (72–146), Antithrombin 3 110 %(80–120) and Activated P C Resistance was 1.9(2.0–4.3). The Hams test was negative but the Anticardiolipin antibody test was positive. IgM level was 52 (normal is up to 10) and IgG was 18.8 (normal is up to 10). She also had border line APC Sensitivity 1.9 (2 to 4.3). Kaolin time 49 sec (70–120) Ktmix 64 sec (70–120), thyroid function test revealed TSH 0.32 mu/L, fT4 20.2 pmol/L (10–25). Subsequent determination of Anticardiolipin antibody was negative. Her symptoms were settled with the use of simple analgesia and she was discharged home with long-term anticoagulation medication. The INR target for long-term anticoagulation was aimed at >3.
Conclusion
This case presented to us as an acute abdominal pain. Subsequent investigations revealed the presence of splenic infarction. Coagulation risk factors for thrombosis proved negative. Haematological investigations revealed the presence of anticardiolipin antibodies at the first instance but subsequent determinations were negative. Hence, it mimicked Hughes syndrome initially but the criteria for temporal persistence of anticardiolipin antibody was not fulfilled. Unusual surgical presentation of a thrombotic abnormality as abdominal pain due to splenic infarction.
doi:10.1186/1471-2326-6-1
PMCID: PMC1458326  PMID: 16603067
25.  Thrombophilic factors are not the leading cause of thrombosis in Behçet's disease 
Annals of the Rheumatic Diseases  2004;63(11):1445-1449.
Background: Venous and arterial thromboses occur in patients with Behçet's disease and are associated with significant morbidity and mortality. Studies on a possible association between the occurrence of thrombosis and thrombophilia in patients with this disease have been controversial.
Objective: To determine the prevalence of the most common thrombophilias and dyslipidaemia in patients with Behçet's disease with and without thrombosis.
Methods: Blood samples from 107 patients with Behçet's disease who had or did not have thrombosis were analysed for factor V Leiden, prothrombin G20210A polymorphism, methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism, factor VIII level, homocysteine and C reactive protein concentrations, dyslipidaemia, and plasma glucosylceramide.
Results: There was no difference between patients with and without thrombosis in the prevalence of prothrombin G20210A polymorphism, factor V Leiden, homozygous MTHFR C677T, or plasma concentrations of homocysteine, C reactive protein, or glucosylceramide. In contrast, patients with thrombosis were found to have significantly higher mean levels of factor VIII, total cholesterol, triglycerides, VLDL cholesterol, and apolipoproteins B-100, C-II, and C-III than those without thrombosis. Multistepwise logistic regression analysis showed that triglyceride concentration was the best marker associated with thrombosis (p = 0.008), with an estimated odds ratio of 1.58 (95% confidence interval, 1.09 to 2.30) for a difference of 40 mg/dl.
Conclusions: Thrombophilia does not seem to play a major role in the tendency to thrombosis in Behçet's disease. However, dyslipidaemia, predominantly hypertriglyceridaemia, might be a risk factor.
doi:10.1136/ard.2003.014241
PMCID: PMC1754810  PMID: 15479893

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