March 7, 2006 - Mental stress has long been suspected of playing an important role in heart disease, and now new research suggests that this might be true for some patients more than others.
Researchers from the University of Florida found that about a third of the patients with known coronary artery disease in their study experienced decreased coronary blood flow while they were under mental duress, even though they performed well on treadmill stress tests or chemical cardiac stress tests. The coronary arteries supply oxygen-rich blood to the heart muscle itself.
Decreased blood flow to heart muscle -- known medically as cardiac ischemia -- deprives heart muscle of oxygen, which can be a warning for a future heart attack. Ischemia may or may not cause a person to feel chest pain. Physical and chemical stress tests are used to check for ischemia.
Several previous studies by the University of Florida research team indicate that mental stresses are among the most important risk factors for death in heart patients. In one study, the researchers found that for some heart patients, mental stress is as dangerous as smoking cigarettes or having high cholesterol.
"We believe the phenomenon of mental-stress-induced reductions in blood flow to the heart is much more common than has been previously recognized," says researcher David S. Sheps, MD, MSPH.
Measuring Mental Stress
Fourteen men and seven women with coronary artery disease were included in the study, and all of them had a recent negative stress test result, meaning that they showed no evidence of decreased blood flow during a treadmill or chemical stress test.
"These would be the people who would generally be believed to have a good prognosis," Sheps tells WebMD.
But when the patients participated in a test designed to measure mental stress, six of the 21 (29%) showed evidence of decreased blood flow. None experienced chest pain during the mental stress test.
All 21 people included in this study had known coronary artery disease, with exercise or chemical stress tests within six months prior that showed no evidence of ischemia. Participants were asked to imagine a stressful situation that was unique to their lives. They were then given two minutes to prepare to deliver a four-minute speech about the situation. Blood pressure was measured and electrocardiograms taken every minute during the speech and for 10 minutes afterward. Heart imaging scans were also performed to check for ischemia.
"The results tend to support [the idea] that mental stress works through a different mechanism than physical stress," Sheps says.
But he is quick to point out that the study says little about the clinical implications of mental-stress-related reductions in blood flow to the heart.
The patients in the study, as well as 300 others participating in a similarly designed study, will continue to be followed in hopes of answering this question.
The researchers are also conducting a study to determine if efforts to reduce mental stress have an impact on cardiovascular outcomes.
The study was funded by the National Institutes of Health and the drug company Bristol-Myers Squibb and was reported in the March issue of the Journal of the American College of Cardiology.
Impact of Wars and Disasters
Mental stress is not officially recognized as a contributing factor in heart disease by many health groups, including the American Heart Association.
While acknowledging that "managing stress makes sense for a person's overall health," it is the AHA's position, a spokeswoman tells WebMD, that there is not yet enough clinical evidence to recommend the use of stress management for the treatment of cardiovascular disease.
There is plenty of anecdotal evidence linking mental stress to heart attacks and sudden death from cardiovascular causes, however, including reports of dramatic rises in such deaths after disasters like Hurricane Katrina, 9/11, and the bombing of Israel during the first Gulf War.
Six months after Hurricane Katrina, it is apparent that many victims died not from the hurricane, but from physical causes brought on by the stresses associated with it.
According to Louis Cataldie, MD, who is acting state medical examiner for Louisiana, a disproportionate number of the roughly 1,300 confirmed Katrina deaths occurred among older people, and most victims did not drown.
In an interview with WebMD, Cataldie confirmed previous news reports that nearly 40% of the victims were over the age of 70. Almost 200 of the victims were evacuees who died outside the state within about a month of the hurricane.
Although the exact cause of death for many Katrina victims will never be known, Cataldie says mental stresses probably played a role in many deaths.
"That certainly seems to be the case," he says.
In a 1991 study, researchers in Israel reported a sharp rise in heart attacks and sudden deaths in Tel Aviv during the Iraqi missile attacks of the first Gulf War. They noted that the increase lasted only a few days, after which time the incidence of heart attacks and deaths returned to normal.