According to the research team, this may be the first randomized trial to demonstrate that a non-pharmaceutical approach can have positive effects on such physiological determinants of cardiovascular health as blood flow to heart, the responsiveness of the lining of blood vessels and the ability of the cardiovascular system to regulate surges in blood pressure.
"While studies have shown that psychosocial factors such as depression, stress and anxiety place heart patients at a much greater risk of suffering future cardiac events or dying, few have looked at the effects of modifying psychosocial factors," said Duke medical psychologist James Blumenthal, Ph.D., lead author of a study appearing in the April 6, 2005 issue of the Journal of the American Medical Society. The trial was supported by a $4.3 million grant from the National Institutes of Health.
"Our results suggest that exercise and stress management training offer considerable promise for patients with heart disease by not only improving psychosocial functioning and reactions to mental and physical stressors, but also by modifying important bio-markers of risk that may translate into improved clinical outcomes," he said.
The Duke trial enrolled 134 patients with stable heart disease and randomized them to one of three groups – exercise, stress management or standard medical therapy. Patients randomized to the exercise group participated in 35 minutes of supervised aerobic exercise training three times a week for 16 weeks. Those in the stress management arm received 16 weekly 1.5-hour classes designed to help patients recognize the sources of stress in their everyday lives and to teach them strategies to respond more adaptively to those stresses.
Patients enrolled had stable heart disease, meaning they did not experience chest pain while at rest, and exhibited evidence of myocardial ischemia, or reduced blood flow to the heart, during exercise. All participants underwent a battery of psychological and physiological testing before randomization, which was repeated four months later.
One of the physiological markers studied was the endothelium, which forms the inner lining of the blood vessels and controls how the vessels reacted to changes in blood flow and pressure. The researchers took ultrasound images of the brachial artery of the arm before and after a tourniquet was applied and released to determine how the vessels responded. Healthy arteries will dilate to accommodate the increased blood flow, while diseased arteries are less responsive, the researchers said.
In these tests of flow-mediated dilation, patients who received the behavioral treatments displayed nearly a 25 percent improvement when compared to those patients who only received usual medical care.
"To our knowledge, this is the first study to show that stress management might reduce cardiovascular risk in part through beneficial effects on vascular endothelial function," Blumenthal said. "This is a level of improvement is comparable to that achieved in drug trials. For that reason, these findings add additional support for the use of non-pharmaceutical approaches to treating patients with heart disease."
The researchers also found that patients who received exercise training or stress management had improved baroreflex sensitivity, a phenomenon by which receptors located along the walls of blood vessels respond to changes in blood pressure. These receptors are connected to the heart by nerves, which carry the message to pump faster or slower in response to pressure changes.
"This finding is important because past studies have demonstrated that abnormally low baroreflex sensitivity has been shown to be associated with worse outcomes for patients with heart disease--improvement may produce clinical benefits," Blumenthal said.
Additionally, the researchers measured changes in the left ventricle -- the pumping chamber of the heart -- during periods of both mental and physical stress. The research team used radionuclide imaging tests to identify wall motion abnormalities (WMAs). These WMAs, or areas of abnormal contractions of the left ventricle, are known indicators of ischemia.
"While there was no difference in WMA scores between the three groups during mental stress testing, among the subgroup of patients who had mental stress-induced WMAs before treatment, those in the exercise and stress management groups had lower WMA scores after treatment compared to patients in usual care."
Other findings, which were expected, showed that patients in the exercise group had the largest improvements in such measures as exercise duration and aerobic capacity. For the psychosocial tests, the researchers found that exercise and stress management had reduced general distress and depression compared to usual care controls.
Future studies are planned to determine if stress management and exercise together have an even greater positive effect on these markers of cardiovascular health. The researchers also said further investigation is needed to reveal the biological mechanisms behind the improvements seen.
Other Duke members of the team were Andrew Sherwood, Ph.D., Michael Babyak, Ph.D., Lana Watkins, Ph.D., Robert Waugh, M.D., Anastasia Georgiades, Ph.D., Simon Bacon, Ph.D., and Edward Coleman. Other members were Alan Hinderliter, M.D., University of North Carolina-Chapel Hill and Junichiro Hayano, M.D., Nagoya City University Hospital, Nagoya, Japan.
Journal
JAMA