Psychological depression appears to contribute to worse medical outcomes for patients with heart failure, ranking it in importance with such risk factors as high cholesterol, hypertension, and even the ability of the heart to pump blood throughout the body.
After taking into account such factors as disease severity, the strength of the heart muscle contractions, the underlying cause for the heart failure, age and medication use, a team of Duke University Medical Center and University of North Carolina researchers found that symptoms of depression were common in this population, and that depressed patients were over 50 percent more likely to die or be hospitalized for their heart condition than patients who were not depressed.
Heart failure, also known as congestive heart failure, is marked by the inability of the heart muscle to pump enough oxygen and nutrients in the blood to the body's tissues. A variety of factors can cause heart failure, including infections of the heart, coronary artery disease, high blood pressure, previous heart attacks and a malfunctioning heart valve. An estimated 4.7 million Americans have heart failure, with 400,000 new cases reported each year, and it is the only cardiovascular disease that is rising in incidence, according to the researchers. About half of heart failure patients will die within five years of diagnosis.
"While many studies have linked depression to worse outcomes for patients with heart disease, there has been uncertainty about the extent to which depression is related to the adverse medical outcomes independent of known medical risk factors," said James Blumenthal, Ph.D., co-author of the study and a clinical psychologist at Duke.
The researchers reported the results Monday in the Monday, Feb. 26, 2007 edition of the Archives of Internal Medicine. The study was funded by the National Institutes of Health.
For their study, the researchers enrolled 204 stable heart failure patients. Each patient took a standard battery of psychological tests to assess symptoms of depression. Forty-six percent demonstrated significant depressive symptoms. Patients were followed for an average of three years. During that time, 26 percent died and 48 percent were hospitalized at least once for their heart condition.
What made this analysis different from other such studies was that the researchers coupled the psychological assessment with a relatively new blood test that measures what are known as "B-type natriuretic peptides." These chemicals are released into the bloodstream by the heart tissue when the heart is unable to pump effectively. The chemicals serve as a signal to the kidneys to produce more urine, which in turn reduces the volume of blood fluid, making it easier for damaged or weakened heart muscle to pump blood.
Elevated levels of B-type natriuretic peptides have been previously shown to be associated with increased risk of death for heart attack patients and are now being used in the diagnosis of heart failure.
"As expected, high levels of BNP predicted worse outcomes in our study, but even taken this and other disease makers into account, we found that depressive symptoms were still independently associated with worse outcomes," said study lead investigator Andrew Sherwood, Ph.D., medical psychologist. "Our findings underscore the importance of assessing heart failure patients for depression, so that where treatment is indicated, both the quality and quantity of their lives may be improved.
Researchers still don't understand why depressed heart patients have worse outcomes. Among possible factors, depressed patients are known to have overly active immune systems, a decrease in the ability of their blood platelets to clot properly and a decrease in their heart's ability to react appropriately to the stresses of everyday life. Depressed patients also may be less likely to comply with their medical treatments, may not be as motivated to stick with exercise or rehabilitation programs, may miss doctor's appointments and tend to make unhealthy lifestyle choices in such areas as diet and smoking.
In an attempt to better understand the role of depression in the fate of heart patients, the researchers are currently enrolling patients in a new clinical trial to measure the effects of exercise and antidepressant medications on specific physiological indicators of heart disease. The trial, supported by the National Institutes of Health, has been dubbed UPBEAT -- short for "Understanding the Prognostic Benefits of Exercise and Anti-Depressant Therapy in persons with cardiac disease." Patients with stable coronary disease and symptoms of depression receive 16 weeks of exercise or pill therapy.
The researchers believe that the results of their current analysis, as well as their ongoing trial, will provide guidance for physicians in treating patients with heart failure and coronary artery disease who are also exhibiting signs of depression.