Global Perspectives
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| DEPRESSION AND HEART DISEASE Compiled by Dr. Nilesh Shah Depression is a common problem in patients with heart disease. Yet only recently have scientific studies examined the relation between them. The evidence suggests that in patients with coronary artery disease, depressive symptoms are associated with increased rates of morbidity and mortality. The link between depression and heart disease is not clearly understood. It may be that patients who suffer post-infarction depression cannot cope with the chronic condition of heart disease. Or it may be that certain biologic factors associated with depression lead to a deterioration in cardiac health. Biologic studies of depression and clinical trials such as ENRICHD (Enhancing Recovery in Coronary Heart Disease), designed to determine the effect of treating depression and social isolation on subsequent mortality and reinfarction, are expected to elucidate the underlying mechanisms. In the meanwhile, data continue to accumulate on the adverse effects of depression on mortality, pain perception and quality of life in patients with ischaemic heart disease. Impact on Mortality Rate In 1993, in a landmark study, Frasure-Smith et al showed that major depression after myocardial infarction is an independent risk factor for mortality at 6 months. The increase in the mortality rate, by a factor of 3 to 4, was equivalent to that of left ventricular dysfunction (Killip class) and history of previous MI. Re-evaluation of the patients at 18 months after discharge from hospital also showed similar results. A recent study (Kaufmann et al) attempted to replicate the work by Frasure-Smith. Additionally, the investigators tried to assess how frequently hostility is associated with depression and whether it is an independent risk factor for death in patients with MI. The study subjects comprised 331 patients (average age 65 years) diagnosed as having acute MI by standard criteria and treated in hospital during a one-year period. Within a week of admission, they were interviewed by trained research assistants who collected baseline social and demographic information and administered (1) a modified version of the National Institute of Mental Health Diagnostic Interview Schedule (DIS) for diagnosing major depression, and (2) the Cook Medley Hostility scale for diagnosing clinical hostility. At 6 months and 12 months after the index MI, the patients were contacted at home, to assess the survival status. Of the 331 patients, 90 (27.2%) met the criteria for clinical depression, while 300 (90.6%) met the criteria for clinical hostility. In the first 6 months 15 patients died, 7 (7.8%) from the group with depression and 8 (3.3%) from the group of 241 patients not clinically depressed. At 12 months, 14 (16.1%) of the 87 clinically depressed patients and 19 (8.2%) of the 231 without depression were dead. The prevalence of clinical hostility was high in those who lived and died, and the difference was not statistically significant. Clinical depression had a significant univariate relation with death at 12 months, but not at 6 months. The multivariate independent predictors of death at 12 months were left ejection fraction, history of chronic heart failure, a previous stroke and diabetes. The authors concluded their report by emphasising that depression is associated with a higher 12-month mortality rate after MI, although it is not a statistically significant predictor after adjusting for other variables. Impact on Chest Pain Perception. A second paper published recently (Ludwig et al) explored the relation between chest pain perception and depression in patients 6 months after acute myocardial infarction. Explaining the reasons for undertaking the study, the authors stated that as angina is an important risk factor in MI patients, identifying the extracardiac factors influencing perception of anginal pain would help physicians to treat the condition more effectively. In the prospective, nonrandomised cohort study, 337 patients (average age 54 years) underwent baseline investigation within 3 weeks of the acute event and follow up after 6 months. Data collected included electrocardiographic recordings, laboratory results and nature of complications. The enrolling physician assessed preinfarction angina and recorded the period of onset. The affective state of the patients was studied using standard instruments to screen for major depressive symptoms. Based on the depression status at baseline investigation, the patients were divided into groups with low (63.2%), moderate (22.3%) or severe (14.5%) degrees of depression. When the patients were reassessed after 6 months, 199 (53%) reported symptoms of anginal pain. Electrocardiographic data at initial testing and somatic risk factors such as high blood pressure and diabetes did not predict post-infarction angina. However, patients with high levels of depression at initial testing had an almost 3-fold risk of having angina pectoris 6 months after the index event. Older age, lower social class status (blue-collar workers), and pre-infarction angina were also significantly related to angina pectoris at the end of the study. According to the authors, their work contributes evidence "to the hypothesis that the perception of chest pain may be triggered not only by the nociceptive stimulation of the ischaemic heart but also by extracardiac sources." However, they are unable to explain how depression affects pain sensitivity and reporting. Impact on Functional Status Coronary artery disease (CAD) is associated with significant functional impairment and disability. Depression is also known to adversely affect activities of daily living, especially in the elderly. However, there is paucity of data on the effect of major depression on functional status in CAD patients. A group of researchers (Steffens et al) recently published a study aimed at filling this lacuna. The authors assessed functional status on the basis of (1) instrumental activities (IADL) and (2) self-maintenance activities of daily living (ADL). IADLs cover functioning in the home and in society as well as physical ability. Self-maintenance ADLs refer to the ability to care for oneself, for example, to eat, dress, bathe, and use the toilet. The study was carried out in a group of 335 inpatients with clinically confirmed coronary artery disease. They were administered a structured interview for depression, the Duke Depression Evaluation Schedule, the Cumulative Illness Rating Scale, and two scales for measuring IADL and self-maintenance ADL. Twenty-seven (8%) of the 335 subjects met DSM-IV criteria for current major depression. Depression was associated with impairment of both self-maintenance and instrumental ADLs. The subjects with major depression were more than twice as likely to report a self-maintenance ADL deficit and were significantly more likely to report an IADL deficit than were non-depressed patients. "The main finding of this study is that CAD patients with major depression report significantly greater disability than CAD patients without depression when controlled for age, gender and medical illness severity," the authors stated. Comments All three studies demonstrate that a fundamental link exists between heart disease and depression. However, the basis of this association remains speculative. It has been suggested that that changes in the autonomic nervous system and platelets seen in depression may be partly responsible for the association. The results may have important clinical implications. If further confirmed by longitudinal studies, clinicians caring for cardiac patients may need to screen for depression and, if present, treat it aggressively. As the paper by Kaufmann et al concludes: "Studies involving treatment of depression need to be undertaken to identify if such interventions could decrease the mortality rate after MI." References
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