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Research to date indicates that the number of coronary artery bypass graft (CABG) surgery patients affected by depression (i.e., major, minor, dysthymia) approximates between 30% and 40% of all cases. A longstanding empirical interest on psychosocial factors in CABG surgery patients highlights an association with increased risk of morbidity in the short and longer term. Recent evidence suggests that both depression and anxiety increase the risk for mortality and morbidity after CABG surgery independent of medical factors, although the behavioral and biological mechanisms are poorly understood. Though neither depression nor anxiety seem to markedly affect neuropsychological dysfunction, depression confers a risk for incident delirium. Following a comprehensive overview of recent literature, practical advice is described for clinicians taking into consideration possible screening aids to improve recognition of anxiety and depression among CABG surgery patients. An overview of contemporary interventions and randomized, controlled trials are described, along with suggestions for future CABG surgery research.
The benefits of coronary artery bypass graft (CABG) surgery with respect to survival, improved ventricular function, freedom from angina and re-stenosis in coronary artery disease (CAD) populations are well established. With an estimated 408,000 CABG surgery procedures performed in the USA alone, evidence suggests that between 30% and 40% of CABG surgery patients experience a form of psychological depression immediately leading up to and after surgery.– The longstanding focus on psychosocial factors in CABG patients has highlighted an association with increased risk of morbidity in the short and longer term. This contemporary review describes the prevalence of depression and anxiety symptoms, and disorders, among CABG surgery patients. Practical advice is described for clinicians taking into consideration potential screening aids to improve identification of anxiety and depression among CABG patients. An overview of research documenting the deleterious impact of psychosocial factors upon cardiac and neuropsychological morbidity and mortality within the acute peri-operative period, and in the longer term, is then covered, describing possible patho- physiological mechanisms. Finally, current treatment intervention studies are described along with suggestions for future CABG surgery research.
Unipolar depression is characterized by depressed mood and/or loss of interest or pleasure, among other symptoms. The reported 15% to 20% prevalence of uni-polar depression among CABG surgery patients is consistent with that found generally among cardiac patients. Comparatively, the point prevalence among the general population is 5% to 9% for females and 2% to 3% among males suggesting CABG surgery patients have higher prevalence of depression than community samples. Though CABG surgery is indicated for increasingly older patients with substantial co-morbidity in contemporary surgical practice, depression has surprisingly been associated with patients of younger age, and female gender. Far less research has been devoted to minor depressive episodes and dysthymia, with the latter reported between 13% and 18% of CABG surgery patients., Collectively, research to date indicates the number of patients affected by any depression (i.e., major, minor or dysthymia) is approximately between 30% and 40% of CABG surgery patients, a summary of which is provided in Table 1. Studies thus far reporting depression prevalence are not without limitations and could be improved. Connerney and colleagues employed a modified diagnostic criteria based on only several days of symptoms immediately post-CABG, thereby potentially inflating prevalence estimates. Other studies employing diagnostic criteria have rarely recruited more than 100 patients,, while others less than 50 patients,,, suggesting larger samples are required.
CABG studies reporting prevalence of depression and anxiety with structured diagnostic interview.
Studies employing self-reported depression measurements suggest up to 50% of patients experience depression symptoms.– Wide variations in the choice of self-reporting measures and dichotomous cut-points to establish depression cases highlight how heterogeneity has contributed to unwieldy estimates. Studies employing self-reported measurements do not reflect a clinical diagnosis of depression, but rather depression symptoms. A lower level of depression symptoms after surgery may reflect the upturn in mood associated with improvements in physical condition from revascularization. However, some patients may develop new depressive symptoms over the course of recovery from surgery. McKhann et al. showed between 13% and 9% of 124 CABG patients at one month and twelve month follow up, respectively, reported clinically relevant depressive symptoms not evident at the time of surgery. Peterson et al. explain newly developed depressive symptoms resulting from the stressors of surgery that can produce an adjustment response, or reactive type depression. In any case, as described below, identifying depression in the CABG surgery patient is complicated by the somatic symptoms experienced in CAD and the physical stressors of surgery.
Self-reporting estimates of anxiety are also variable. Anxiety is particularly high for CABG patients while on the waiting list with an unknown surgery date. Fear of dying before, rather than during surgery, has been highlighted as a pervasive and anxious preoccupation., Anxiety also manifests as an autonomic symptom that can exacerbate CAD symptoms. After surgery, while anxiety may decrease to below pre-operative levels, the severity of anxiety does not necessarily remit to below sub-clinical levels and may warrant intervention. Like depression, complicating and accurate identification of anxious patients over the course of surgery recovery is the finding that autonomic-arousal symptoms significantly increase after CABG. This is hardly surprising given the overlap and seemingly indistinguishable nature of CAD and somatic anxiety symptoms (e.g., breathlessness, increased heart rate). A caveat of research to date is the use of non-specific self-reporting measurements that do not reflect the characteristics of any particular anxiety disorder, but rather a nebulous, often ill-defined, construct, similar to “stress”.
The most common anxiety disorders appear to be generalized anxiety disorder (GAD), a disorder marked by pervasive worry, and panic disorder, a disorder marked by recurrent panic attacks. Both GAD and panic disorder are variably reported from zero prevalence to nearly 11% of CABG surgery patients (see Table 1).,,, To date, emphasis on panic disorder and GAD is possibly the result of recognition of their higher prevalence, and also, that each disorder is generally associated with adverse cardiac outcomes among CAD patients., With respect to other anxiety disorders in CABG patients, it is estimated that between 2.5% and 4.3% meet the criteria for social phobia;, and between 0.6% and 2.1% meet criteria for obsessive compulsive disorder., Less is known regarding phobic disorders among CABG patients and only one study reported 1.3% prevalence of specific phobia. The above mentioned literature highlights the requirement for rigorous psychiatric evaluation among larger CABG surgery samples to determine the prevalence of anxiety disorders.
Recently, particular research interest has focused on post- traumatic stress disorder (PTSD) in CAD and CABG surgery patients. One of the unique diagnostic features of PSTD is subjective experience or witness to, an extremely traumatic event. An audit of 62,665 electronic medical records suggested post-traumatic stress disorder was prevalent in 14.7% of CABG patients. Prospective studies with structured psychiatric assessments have reported far lower pre-operative levels of PTSD, varying between 0.6% before surgery and 9.0% at one month post-operatively. PTSD symptomatology, including traumatic memories related to CABG surgery, was evident in up to 18% of 148 patients at six month follow- up. As most PTSD symptoms were incident cases, the data suggest that exposure to the CABG surgical procedures and in-hospital stressors may contribute to PTSD etiology. That being said, research among 63 Holocaust survivors with PTSD symptoms at the time of CABG has suggested that such individuals can also achieve improvements in quality of life despite significant preexisting PTSD symptoms.
A survey of 796 cardiovascular physicians determined 71.2% of respondents asked fewer than half of their patients with CAD about depression. Some authors have recommended depression screening following CABG surgery as a way to improve pathways to recovery, though the American College of Cardiology and American Heart Association 2004 guideline update on CABG surgery highlight that pre-operative screening may simply sensitize staff and family members to post-operative distress and mood changes. The American Heart Association recently indicated that evidence exists for depression screening in CAD patients, stating it is reasonable in instances where patients have access to case management, in collaboration with their primary care physician, and a mental health specialist. Thus, we strongly recommended that suitable follow-up, referral and psychosocial intervention pathways are in place prior to commencing with routine screening among CABG surgery patients. As such, not every cardiac surgery unit or medical centre could feasibly adopt a routine depression screening and follow-up protocol. Also, current evidence seems premature to support the premise that routine depression screening in CAD leads to an improvement in cardiac outcomes and furthermore no such evidence exists for anxiety. Clinicians are encouraged to prudently use their own judgment to consider psychiatric intervention for depression and anxiety disorders once identified in the CABG surgery patient, or any other CAD patient, regardless of impact upon cardiac prognosis.
The American Heart Association has recommended self- reporting measures to aid rapid identification of likely depressed patients. The Patient Health Questionnaire (PHQ) is one such depression assessing measurement, available in English and Spanish, as a two-item screener (PHQ-2), to tap into the two requisite symptoms for a depression or major depressive episode diagnosis, i.e., (1) little interest or pleasure in doing things, (2) feeling down, depressed, or hopeless. In its expanded form, the PHQ-9 covers the full spectrum of symptoms reflective of major depression as depicted in Table 2. As Carney and Freedland point out, many different combinations of symptoms fulfill criteria for a major depressive episode. Certainly, close monitoring and follow-up for patients describing thoughts of death or self harm is strongly recommended. Shemesh et al. reported that more than 12% of cardiovascular patients require immediate evaluation of suicidal thoughts and intent, reiterating the practical requirements for appropriate referral pathways following assessment.
Core depression symptoms assessed by PHQ-9.
It has been suggested that a positive response to either of the PHQ-2 questions should be followed up with administration of the PHQ-9, with scores of ≥ 10 on the PHQ-9 requiring an even more comprehensive assessment, such as by a psychiatrist or psychologist. As previously mentioned, the somatic laden, depression diagnostic criteria overlap CAD symptoms. Specifically, fatigue, loss of appetite, psychomotor retardation, insomnia, and difficulty concentrating can be the direct physiological response to a medical illness and hospitalization and have been documented to significantly increase in the first month after CABG surgery. Brief psychological reactions to the impending stressors of surgery and the post-operative recovery period may spontaneously remit over time, thus requiring no further intervention. Watchful waiting, monitoring and brief support of suspected depressed patients might serve as a useful strategy before implementing psychological intervention. To aid clinicians, the developers of the PHQ-9 have described their own recommendations for what constitutes depression remission and treatment efficacy in primary care populations. With respect to depression identification from self-reporting symptoms vs. structured psychiatric interview, the only study to employ receiver operating characteristics (a type of statistical analysis) in CABG surgery patients showed that a measure of depression yielded an area-under curve of 0.811 and 70.4% for sensitivity and 77.1% for specificity in the detection of major depression. Without more research, the utility of self-reporting measures to identify depression in CABG populations remains largely unknown.
Identification of anxiety disorders, such as GAD, panic disorders and PTSD, is more complicated as each is demarcated by specific criteria of symptoms which are currently under revision in anticipation of the fifth Diagnostic and Statistical Manual of Mental Disorders. The group that developed the PHQ also developed a measurement with items closely matching diagnostic criteria for GAD. Scores of ≥ 10 on the GAD-7 were likely to yield a positive diagnosis. The GAD-7 also demonstrated sensitivity and specificity for identification of a range of other anxiety disorders in primary care patients, such as PTSD and panic disorder. Moreover, the group further described a single question pertaining to panic attacks with sufficient sensitivity and specificity for primary care populations. The question was “In the last four weeks, have you had an anxiety attack-suddenly feeling fear or panic?”. As mentioned above, self-reporting measures are typically non-specific and do not relate to any particular anxiety disorder. Despite an availability of a multitude of anxiety questionnaires, few have been validated as screening tools to identify anxiety disorders in CAD. Favorable sensitivity (90.7%) and specificity (61.4%) was reported for the Hospital Anxiety and Depression Scale anxiety subscale scores of ≥ 8 to detect GAD. A study among CABG surgery patients showed superior receiver operating characteristics (75.0% sensitivity, 72.5% specificity; area-under curve of 0.795) in detection of GAD when the general distress scale of the Mood Anxiety Symptom Questionnaire was used. Conversely, panic disorder was best predicted by somatic anxiety (75.0% sensitivity, 68.5% specificity; area-under curve of 0.784). Apart from a multitude of self-reporting anxiety measurements, more time intensive structured, clinical interviews are also available for a range of anxiety disorders that can be undertaken by a psychiatrist or psychologist.
Comprehensive cardiac research has included meta-analyses detailing etiological and prognostic associations between depression, in particular, and CAD outcomes., Recent depression research among CABG surgery patients are described in Table 3. Several earlier studies corroborate the association between depressive symptoms upon mortality in the longer term., In a study of 309 patients at one year follow-up, Connerney et al. reported that major depression, but not depressive symptoms, were associated with cardiac events. The authors found a more than two-fold greater risk for cardiac events [risk ratio = 2.31, 95% confidence interval (CI) 1.17–4.56] after adjustment for ejection fraction, female, gender, extended length of hospital stay, New York Heart Association class and number of revascularized vessels and living alone. Follow-up of these patients at ten years showed both depression symptoms and major depression increased the risk for cardiac mortality. A similar finding attributable to depression symptoms was reported by Blumenthal et al. who excluded patients with a major depression and psychiatric diagnosis, but nevertheless found that moderate to severe depression symptoms were associated with increased mortality risk (hazard ratio = 2.4, 95%CI 1.2–4.2). Evidence also extends to non-fatal morbidity outcomes, where depression symptoms reportedly increase the risk for unplanned hospital readmissions,,– cardiac events, and poorer quality of life. Scheier et al. reported depressive symptoms associated with surgery, CAD and wound infection resulted in hospital readmissions among 309 patients at six month follow-up. Patients reporting depressive symptoms one month after cardiac surgery were found to have a greater proportion of arrhythmias and return of angina symptoms at five year follow-up. In a study of 963 CABG patients, improvements in physical health at six month follow up were lower among patients with depressive symptoms after adjustment for cardiac severity and baseline health. A systematic comparison of depression, anxiety and stress suggested that only depression was consistently associated with quality of life domains tapping into vitality, social role functioning, physical and general health.
Association between depression and mortality or cardiac outcome after cardiac surgery.
Depression sub-types have also been investigated. Extrapolating whether the timing and course of depression influences post-CABG morbidity, some evidence supports that new onset, and persistent vs. remitted depression symptoms assessed by self-reporting questionnaires pose a greater risk for mortality and cardiac morbidity than brief periods of depression at the time of surgery. With respect to specific clusters of depression symptoms, two recent studies support a prognostic association between cognitive depression symptoms (e.g., pessimism, past-failure, self-criticalness, worthlessness) with nearly a two-fold greater risk of cardiac morbidity and mortality after CABG surgery., These findings curiously suggest that the adverse effects of depression after CABG are independent of any somatic depressive symptoms, or medical related co-morbidity. However, current evidence summarized by Carney and Freedland generally does not confirm that any particular subtype of depression confers greater CAD morbidity risk.
Depression appears to contribute only partly to increased risk for subsequent morbidity after CABG surgery. Not surprisingly, research also implicates anxiety in CABG surgery outcomes,– as depression and anxiety frequently occur in the same individual concurrently and across the lifespan. A study among 62,665 CABG patients showed that 9% of cases with co-morbid PTSD and major depression diagnosis had a greater risk of in-hospital mortality than patients with either PTSD, or major depression alone. However, electronic medical records were employed for a limited range of psychiatric disorders that were not verified with structured psychiatric interview. By contrast, studies that simultaneously assessed both depression and anxiety symptoms, reported that each negative emotional state portended nearly two-fold increased risk of unplanned hospital readmissions., Recently, our group showed pre-operative anxiety was associated with greater all-cause mortality [hazard ratio = 1.88, 95%CI 1.12–3.17] and independent of age, renal disease, concomitant valve procedure, cerebrovascular disease and peripheral vascular disease. Taking these findings further, we showed that anxiety increases odds for incident atrial fibrillation after CABG surgery. Additionally, we found that GAD, but not major depression or panic disorder, was associated with acute in-hospital morbidity events, such as stroke, myocardial infarction and renal failure. Together the results seem to suggest that both depression and anxiety have a role in post-CABG morbidity. However, focusing solely on depression, rather than general psychiatric distress and anxiety, might pose as a barrier to the identification of CABG surgery patients at risk of morbidity and requiring psychological intervention.
Studies to date are not without their limitations. Like depression-CAD studies elsewhere, lack of adjustment for conventional cardiac risk factors, such as left ventricular function, pose a serious caveat to interpreting the role of psychosocial factors upon post CABG functioning. It is likely that adjustment for non-psychological morbidity risk factors is limited by the low number of actual morbidity events experienced among typically small samples with short follow-up. Some studies have also excluded patients with a depression or anxiety diagnosis,, thereby precluding examination of a dose-response effect among the more distressed patients. Unfortunately, these practices tend to bias the results in favor of rejecting the null hypothesis and the resultant wide confidence intervals,,, obscure the effect of study size and the biological plausibility of an effect for depression and anxiety. Research could be improved by addressing the known risk factors for postoperative morbidity and mortality, such as those identified by the Society of Thoracic Surgeons, extending the length of patient follow-up, recruiting more patients, and employing structured psychiatric assessments alongside self-reported distress measurements.
Systematic reviews have also identified depression as a predisposing factor to increase the risk for delirium among cardiac surgery populations. In the hospitalized patient, a delirious state may manifest itself as a fluctuating course of disorientation to time, place and persons, perceptual disturbances and hallucinations. Delirium is the most common psychiatric disorder observed upon admission to healthcare settings. The incidence of delirium after cardiac surgery is reportedly between 3.1% and 50%,,– depending on the timing and criteria for diagnosis. McAvay and colleagues showed that dysphoric mood and hopelessness and depressive symptoms were associated with incident delirium after hospitalization. A prognostic study for 158 CABG patients showed that even when diagnostic criteria for delirium is modified to reduce bias from overlapping delirium-depression symptoms, pre-operative major depression remained associated with incident delirium after CABG surgery. In explaining recent findings, Davydow suggested a bidirectional relationship whereby persons may develop subsequent distress as a response to in-hospital delirium. Surprisingly, related research concerning depression and anxiety in post-CABG neuropsychological functions has produced predominantly null findings from relatively small samples. Though post-operative neuropsychological dysfunction has been exhaustively documented,,, only weak correlations have been reported between depression, anxiety and cognitive function in the short term, and long term., At six month and five year follow-up, neither depression, anxiety, or stress was consistently associated with neuropsychological dysfunction in regression analysis among 75 CABG surgery and 36 control patients. The above results suggest that while psychological factors, such as depression might play a role in delirium, these are not consistently associated with neuropsychological functions.
An increased risk in CAD morbidity attributable to emotional distress is likely explained by both behavioral and biological mechanisms. With respect to the former, epidemiological surveys suggest that affective disorders are associated with larger body mass index, hypertension, hypercholesterolemia, diabetes, physical inactivity and regular smoking and nicotine dependence., Despite a greater proportion of co-morbidity and clinical risk factors, patients with emotional distress and co-morbid CAD are also less likely to comply with prescribed medications, such as aspirin. Psychological distress has also been associated with less concordance to exercise regimens and smoking cessation four months after myocardial infarction.
The biological mechanisms of cardio-pathogenesis attributable to depression and anxiety are multifactorial and include the dysregulation of the hypothalamic-pituitary- adrenal axis,– reduced heart-rate-variability,– altered serotonergic pathways, inflammatory response and altered platelet aggregability. An earlier review suggested 20% of variability in CAD and depressive symptoms was attributable to common genetic factors and the authors speculated these could be related to inflammation and serotonin. The association between depression and delirium is explained, in part, by common patho-physiological pathways via the limbic-hypothalamic-pituitary-adrenal-axis, sympathetic nervous system and inflammatory responses suspected to affect cognition, mood and motivation and induce fatigability, anhedonia and reduced appetite.
An encouraging 2006 survey of cardiovascular physicians reported nearly 50% of respondents treat the symptoms of depression once identified in patients with CAD. With respect to pharmacological management, clinicians should be aware of the possible pro-arrhythmic and cardio-toxic effects of tricyclic anti-depressants in cardiac patients., Selective serotonin re-uptake inhibitors (SSRI), on the other hand, have been hypothesized as safe among cardiac patients due to the serotonin transporter affinity and attenuation of platelet functioning. Safety, tolerability and efficacy of SSRIs among cardiac patients have been reported in some studies,, but not others.– The possible risks attributable to SSRIs for CABG surgery patients specifically include increased bleeding, but has not been consistently supported., One study suggested an increased mortality and readmission risk after CABG surgery attributable to SSRIs. Another recent study indicated greater renal morbidity and ventilation times, but not greater mortality risk. Two recent systematic reviews of randomized, controlled trials (RCT) in CAD patients both corroborated SSRI vs. placebo were not associated with reductions or increased risk in mortality and differential findings were reported with respect to hospital readmissions. One found a reduced odds [pooled odds ratio (OR) = 0.58, 95%CI 0.39–0.85], whereas another review did not when applying a stringent criteria for properly randomized studies (risk ratio = 0.74, 95%CI 0.44– 1.23). Depression symptom efficacy for SSRI vs. placebo was supported by a pooled standardized mean differences of -0.24 (95%CI: -0.38 to -0.09).
Depression is an important predictor of participation in, and completion of, cardiac rehabilitation among CABG surgery patients and thus may form a barrier to improvements in cardiac functioning. A diverse range of behavioral and psychological RCT interventions have been reported and cognitive behavioral therapy or collaborative care constitutes Class IIa evidence (i.e., it is reasonable to administer treatment, additional studies with focused objectives are needed). Prior to CABG surgery, interventions have typically focused on anxiety. A non-psychological educational intervention before surgery had little impact on anxiety and depression. By contrast, an intervention consisting of information and emotional support was found to impact depression and anxiety in the longer term. In a Canadian study, eight weeks prior to CABG, an intervention consisting of nurse initiated education and support, in addition to exercise training (n = 113), was not associated with differences in pre-surgery anxiety versus usual care (n = 107). Post-operative interventions have typically focused on depression as the primary psychological factor., Freedland et al. compared cognitive behavior or supportive stress management vs usual care and found significant three month depression remission rates in the treatment arms (71%, 57%, and 33% respectively, P = 0.002). Group differences were sustained at nine month follow up while cognitive behavioral therapy intervention was found to be superior with respect to measures of anxiety, hopelessness, stress, and quality of life. An eight month, bi-weekly, nurse-led telephone delivered intervention for depressed patients reported modest effect sizes for mental health quality of life (0.30; 95%CI 0.17– 0.52), but reported exceptionally low mental health service visits (4% intervention vs. 6% usual care). Lie et al. in a RCT reported no differences in quality of life or distress measures between patients receiving nurse-led education with psychological support intervention (n = 93) and patients receiving usual care (n = 92). However, the brief intervention was restricted to four home visits at two and four weeks post-operatively. Significantly lower depression levels among a control group (n = 90) compared to an exercise and behavior modification group (n = 94) challenge the benefits of components, such as behavioral activation alone, for reducing depressive symptoms post CABG surgery.
The limitation of psychosocial RCTs among revascularization populations is that those patients experiencing significant post-operative morbidity are likely to be excluded from trial inclusion. Thus, less is potentially known with respect to the long term treatment outcomes for patients who experience stroke, deep sternal wound infection, sternal dehiscence, renal failure requiring dialysis and extended length of time on mechanical ventilation, or intensive care during their hospital stay. These moribund patients face high risks for developing or exacerbating psychological distress. Also, though treatment of affective distress is important in any context, it has not been sufficiently investigated whether interventions among cardiac patients can promote and maintain health related behavior change. Finally, beyond clinical trials, potential barriers to the implementation of patient support, include hospital culture and psychiatry registrar or allied health professional workload, in addition to mental health service accessibility and cost, cardiologist and surgeon preference and overlap with cardiac rehabilitation services.
How can prognostic studies using a once off assessment of psychiatric disorders and psychological distress show an increase in the risk for morbidity and mortality months and years after CABG surgery? The behavioral and physiological mechanisms, such as smoking, alcohol use, diet, compliance to medication and exercise regimes, along with inflammatory processes, are possible explanations warranting further research in CABG surgery cohorts. Unfortunately, contemporary understandings of the risks of depression and anxiety in CAD are constrained by a predominantly biomedical model. Further consideration for the interaction between these disorders and social factors, such as socio-economic status, ethnicity, living alone, social isolation, may improve our understandings and uncover fruitful avenues for intervention. Moreover, research to date appears too focused on depression, whereas the limited studies addressing depression and anxiety, simultaneously, warrants further research to acquire and extrapolate cumulative knowledge with respect to psychosocial risk. Collaboration between psychologists and psychiatric specialists with cardiac surgeons, cardiologists and cardiac nurses will enhance the research base and may lead to improved patient outcomes.
In conclusion, between 30% and 40% of CABG surgery patients experience depression and anxiety disorders at rates significantly higher than prevalent in community samples. Both depression and anxiety appear to confer greater morbidity risks, though the behavioral and biological mechanisms are poorly understood. It is commonly hoped that psychosocial intervention might mitigate the deleterious impact of depression and anxiety upon subsequent morbidity and mortality. Accurate diagnosis and intervention among CABG surgery patients may impact upon distress levels and clinicians are encouraged to establish referral and treatment pathways for their own CAD patients.