Depression Increases Risk Of Ischemia During Mental Stress And Stresses Of Everyday Life
Duke University Medical Center researchers have found that heart patients with mild to moderate depression are more likely to experience periods of reduced blood flow to heart muscle during mental stress and the stresses of daily living, a finding the researchers said may help explain why depressed heart patients have worse overall outcomes.
Specifically, the researchers found that these non-physical stresses caused a several-fold increase in ischemia, reduced blood flow to heart muscle, in patients with mild to moderate depression, while the stresses of everyday life also caused increased ischemia in these patients.
Ischemia, which is typically caused by blockages in the arteries that supply the heart with oxygen and nutrient-rich blood, can over time lead to chest pain, heart attacks or death. In many cases, ischemia cannot be felt by the patient, meaning that heart muscle cells can die "silently" each time they are deprived of oxygen and nutrients.
"Depression is relatively common in patients with ischemic heart disease and those who are recovering from a heart attack; and furthermore it has been associated with increased risks of future cardiac events or even death," said Duke researcher Wei Jiang, M.D., who published the results of her study in this month's issue (July 2003) of the American Heart Journal. "However, it has not been clear how depression is involved in these worse outcomes.
"It now appears that depression makes patients with stable heart disease more susceptible to the adverse effects of mental stress and the stresses of everyday life on the heart," Jiang continued. "The challenge for us, in this fast-paced world, is come up with ways to reduce mental stresses, such as exercise, or other pleasurable physical activities."
Interestingly, the researchers found that depressed patients did not exhibit ischemia during exercise testing, leading Jiang to conclude that mental stress and physical stress act on the heart in different ways.
Also, the researchers were surprised to find that the most depressed patients in their study were the least likely to experience ischemia as a result of mental stress or everyday life.
"This could be explained by the fact that the sample size in the severely depressed group (25 out of 135) was too small to make any definitive conclusions," Jiang said. "Also, it could also be that because of the severity of their depression, these patients didn't try as hard during the tests as the other patients. Whatever the reasons are, more research is needed to answer this paradox."
For the study, Jiang first administered the commonly-used Center for Epidemiological Studies - Depression (CES-D) scale to 135 patients with ischemic heart disease. Patients were considered severely depressed if their scored 19 or above on the CES-D. The median score for all patients was 7.
"For the majority of the patients who scored below 19, we saw a corresponding increase in ischemia as the depression score increased, until we reached 19," Jiang explained. "An increase of 5 on the CES-D score was associated with a two-fold increase in the odds of ischemia during mental stress and about a 50 percent increase in ischemia during daily life."
After taking the CES-D test, patients underwent five timed mental tests in the laboratory designed to cause stress or anxiety, such as public speaking and serial subtractions. The patients also exercised on cycle ergometers. During administration of these tests, the researchers obtained visual images of the heart with radionuclide ventriculography as well as electrical measurements with an electrocardiogram (ECG).
The researchers were looking for the occurrence of changes in the heart's pumping chambers known as wall motion abnormalities (WMA), which are used as indicators of ischemia.
"A little more than one-third of the patients (34.1 percent) exhibited stress-induced WMA on at least one of the five mental tests," Jiang explained. "In the exercise tests, 46.6 percent of the patients exhibited WMA. While increased scores on the depression test were associated with increased WMA during mental testing, the same associations were not present for the exercise."
To determine whether the stresses and strains of everyday life were associated with periods of ischemia, all patients were also attached to a portable heart monitor for two days.
During this 48-hour period, 41.7 percent of the patients had at least one episode of ischemia, Jiang said, adding that the results were quite similar to that of the mental stress tests.
DURHAM, N.C. - http://www.dukemednews.org