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.