This finding is important, the researchers said, because this heart beat irregularity, known as ventricular tachycardia, can be a precursor of sudden cardiac death . Interestingly, the researchers found this association between depression and ventricular tachycardia in patients who were relatively healthy and that the risk of ventricular tachycardia increased with increased levels of depression. The researchers also found a link between anxiety and ventricular tachycardia.
Based on the results of their study, the researchers believe that hospitalized heart attack patients should be evaluated for depression, and those who are found to be clinically depressed should have their heart activity closely monitored.
Ventricular tachycardia, which can be treated with such drugs as beta blockers, occurs whenever ventricles beat more than 100 times in a minute. In some cases, the tachycardia may only last for a few beats; however sustained periods of tachycardia can cause ventricular damage needing immediate attention.
Duke research assistant Patrick Smith presented the results of the Duke analysis March 5, 2005, at the annual meeting of the American Psychosomatic Society in Vancouver. The research was supported by the National Heart, Lung, and Blood Institute.
"The results of our analysis showed that depression in patients who have been hospitalized for a heart attack can be a significant predictor of ventricular tachycardia," Smith said. "Also, the finding that scores from commonly used tests of depression and anxiety were associated with the frequency of ventricular tachycardia suggests that depression, anxiety and these potentially life-threatening dysrhythmias are connected."
For the study, the team followed 72 patients admitted to Duke University Hospital with a heart attack. Patients were interviewed by a mental health provider and given standardized tests for depression and anxiety within three days of admission. All patients were then connected to a heart monitor that recorded detailed heart beat information continuously over a 24-hour period.
"We found that almost one in five (18 percent) patients met the criteria for clinical depression," Smith said. "Of those patients deemed to be clinically depressed, 38 percent had at least one episode of ventricular tachycardia, compared to only 10 percent for the non-depressed patients. We also found a strong correlation between the severity of the depression and the number of beats of ventricular tachycardia."
Specifically, the researchers found that based on scores from the commonly used Beck Depression Inventory (BDI), going from a non-depressed state to mild depression conferred an 81 percent higher risk of suffering from ventricular tachycardia.
"We were surprised that we saw such a strong association between depression and ventricular tachycardia in these patients, who were among the 'healthiest' of heart attack patients," said senior researcher Lana Watkins, Ph.D. "We excluded patients whose left ventricle - the main pumping chamber -- was pumping at less than 30 percent of its capacity.
"Given that we saw such a strong association in a relatively healthy population of heart attack patients suggest that depression can be a useful clinical predictor of ventricular tachycardia," she said.
While the researchers cannot determine whether there is a cause-and-effect relationship between depression and ventricular tachycardia, it is known that depression has been linked to activation of the immune system, as well as alteration of the aggregation properties of blood platelets. Depression has also been linked to other such cardiovascular risk factors as insulin resistance, hypertension, obesity, increased cigarette smoking, alcohol abuse and physical inactivity.
The current study is an analysis of a subgroup of patients enrolled in an ongoing investigation led by Watkins that could provide insights into the effects of depression and stress on heart rate variability. Patients whose hearts are unable to appropriately regulate their beating action in response to outside stimuli - such as stress and anxiety - are known to be at higher risk of suffering a heart attack, the researchers said. The researchers hope correlate the clinical data obtained from portable heart monitors worn 24 hours a day with everyday stressors as recorded in a diary.
"I think primary care physicians, as well as cardiologists, are beginning to appreciate the role of psychosocial factors in the coronary artery disease," said Watkins. "What is needed is more of an understanding of the pathophysiology of this association between depression and coronary artery disease. With that information, we can then determine whether or not treating the depression in this group of patients can actually improve mortality."
She said that depressed heart attack patients should have their heart rhythm monitored closely, since medical approaches to treating depression can often take weeks to be effective.
Other Duke colleagues on the study included James Blumenthal, Ph.D., Michael Babyak, Ph.D., Anastasia Georgiades, Ph.D., Andrew Sherwood, Ph.D., Amy Keeler, and Michael Sketch, M.D., and Ranga Krishnan, M.D.