Although national guidelines recommending the use of antithrombotic drugs for DVT prophylaxis and secondary stroke prevention have been in place for many years,16,34,35
we found an overall underutilization of these therapies in eligible elderly patients hospitalized with ischemic stroke, particularly among the oldest patients. Among eligible ischemic stroke patients 85+ years of age, only 11% received pharmacological DVT prophylaxis, 78% received antiplatelet medications, 76% received anticoagulants for atrial fibrillation, and 70% received antithrombotics at discharge. Because we assessed treatment rates among eligible patients, these relatively low utilization rates cannot be attributed to differences in contraindications by age. Decreased mobility and admission from a skilled nursing facility were also associated with lower receipt of each therapy. Race-ethnicity was associated with the rates of DVT prophylaxis, anticoagulant use for atrial fibrillation, and antithrombotic use at discharge, but these associations were inconsistent across race-ethnic groups and treatments. The overall low use of DVT prophylaxis and the reasons for these differences in otherwise eligible patients requires further investigation.
Prior analyses using the National Stroke Project data show that antithrombotics prescribed at discharge for patients with acute stroke or transient ischemic attack and warfarin for patients with atrial fibrillation are underutilized in patients age 65 years or older.23,33
Our analyses extend this prior work, stratifying the receipt of treatment by age groups for the subset of patients with a new ischemic stroke. We found that the underutilization of therapies is even more pronounced for the very elderly, and differs by other patient characteristics including admission location and level of functional dependence. The receipt rate of therapy for atrial fibrillation in our study was higher than that reported by Jencks et al. This is likely due to their consideration of all Medicare patients with a principal discharge diagnosis of atrial fibrillation whether or not they had an ischemic stroke. In contrast, we determined the receipt of therapy among ischemic stroke patients with documented evidence of atrial fibrillation during the hospitalization. Our lower rate of antithrombotic use at discharge as compared with Jencks et al likely reflects differences in inclusion and exclusion criteria.
DVT prophylaxis in immobilized stroke patients can reduce the risk of death due to pulmonary embolism by 56% to 82%.36
Although we found the level of utilization to be consistent with the reported rate of 13.8% among eligible Medicare patients in Michigan,37
they were lower than those reported from the California Acute Stroke Pilot Registry (CASPR, 64% in 2003 and 43% in 2004) and Get-With-The-Guidelines (GWTG)-Stroke (74% in 2003) databases.38–40
Rates may be higher in GWTG-Stroke and CASPR hospitals as they have a particular interest in stroke and both are designed as quality improvement programs. Variation in rates between studies may also reflect differences in the age distributions of included patients, differing criteria for appropriate prophylaxis, as well as the accuracy of assessment and documentation for the level of patient activity by day 2 of the hospitalization. There may also be increased DVT prophylactic use over time, as evidenced by the increase from 13.8–17.9% found in Medicare beneficiaries from 1998–2002,41
and a 15.8% increase in GWTG-Stroke hospitals from 2003 through 2007.38
More than three-quarters of patients who were eligible to receive antiplatelet drugs during the hospitalization received them, with the proportion declining in successively older age groups. These observations are consistent with another study that found unadjusted utilization rates of 73.7% among stroke patients age 65–75 years of age, and 71.9% among those >75 years old; however, risk adjusted analyses combined the older groups and compared them with patients younger than 65 years of age.42
Hierarchical models revealed no difference in the receipt of antiplatelet drugs across age groups during the acute hospitalization.
Direct comparisons with prior research reporting utilization rates of warfarin for in-hospital atrial fibrillation with our study are limited because these other studies either included patients <65 years of age43,44
or those without a diagnosis of acute ischemic stroke.21,23,32,33
A recent study of ischemic stroke patients treated at designated stroke centers in Ontario reported similar rates of treatment as our study, with a non-significant decrease in the receipt of warfarin at discharge (87.2% for <59 years, 81.5% for 60–69 years, 82.7% for 70–79 years, and 76.8% for 80+ years of age).29
Older patients with atrial fibrillation are known to benefit from anticoagulant treatment;45–48
however, we found lower receipt rates in the older age groups. This suggests that patient age may influence physicians’ decisions to prescribe warfarin independent of other demographic and clinical factors, a finding consistent with other reports in older populations.21,43
One explanation for this age difference may be physicians’ desire to avoid hemorrhagic stroke, the risk for which increases with age.22
Although the risk of major anticoagulant-associated bleeding is higher in the very elderly,48
the risks do not offset the benefits for most high risk patients with atrial fibrillation if anticoagulants are carefully administered.45–48
We found that one-fourth of eligible patients did not receive antithrombotic medications at discharge, a rate that is somewhat higher than the 16%-17% reported in two studies of Medicare patients in Michigan during the same time period.24,41
It is possible that our observed rate differs because of local variations in stroke care that are not evident within a single geographic location. Furthermore, the Michigan studies included cases with transient arterial occlusion (ICD-9 code 362.34), restricted stroke cases to white or black race, and excluded cases in which there was physician documentation that at least one antithrombotic therapy was considered but not prescribed.
Volpato et al found no difference in the prescription of antithrombotic therapy at discharge among elderly stroke patients in Italian clinical centers, but did find lower utilization rates with decreased functional independence.27
A Canadian study reported similar rates of antithrombotics at discharge across all elderly age groups (<59, 60–69, 70–79, and 80+), but only included patients admitted to designated stroke centers in Ontario which may represent a higher level of care than in non-stroke center facilities.29
Our findings differ from data reported from CASPR, which found no age difference (80+ vs. <80) in optimal utilization of antithrombotic therapy.49
Optimal therapy was defined as receipt at discharge of at least one medication from the class (i.e., an antiplatelet drug or an anticoagulant) or a valid contraindication to treatment. There was wide variation in the rates of actual and optimal treatment across the 11 CASPR hospitals. The differences in reported results between this study and ours may reflect greater variation in our sample, which was drawn from hospitals across the United States, and/or may represent selection bias (and as noted above CASPR hospitals were selected based on their interest in stroke care and experience in using registries). Higher compliance rates would also be expected among committed hospitals that were aware they were being monitored for these therapies, including those participating in quality improvement programs such as the GWTG-Stroke program.40
Our study has several limitations. First, we may have underestimated the proportion of patients prescribed antithrombotics prior to admission or at discharge due to lack of documentation, particularly for non-prescription medications such as aspirin. We used a conservative approach, excluding patients with a range of potential contraindications for the use of antiplatelet drugs, yet still found a large proportion of untreated patients. Additional clinical contraindications for acute anticoagulation may not have been documented and information on stroke size, which might affect the use of these drugs, was not available. Determining patient immobility from chart review had moderate reliability, and may have influenced the observed rates. The data reflect treatment patterns at the time of the study. Although care may have improved over time, practice recommendations for the use of antithrombotic therapies have not appreciably changed.16,34,35
We did not have information on reasons that physicians may not have prescribed these medications; however, a review of published articles assessing practice patterns and barriers to warfarin use in the setting of atrial fibrillation indicates that advanced patient age is consistently identified as a factor influencing decision making.22
Finally, our findings may not be generalizable to patients who are transferred to or from other facilities as they were excluded from the analysis.
Our findings suggest that antithrombotic medication use is not optimal, and that treatment rates may be affected by patient age as well as other patient characteristics, including admission from a skilled nursing facility and functional status. These differences were present regardless of patient demographics and comorbidities. Further research is needed to replicate these results in other data resources and understand the reasons for these differences. The underutilization of antithrombotic drugs among elderly stroke patients, particularly the very elderly, suggests that there may be an opportunity to improve their post-stroke DVT prophylaxis and secondary preventive care. Future work will need to determine the effectiveness of performance improvement activities such as primary stroke center certification,50
the Get-With-The-Guidelines-Stroke program,40
and other similar efforts in the elderly population.