Under pressure: How stress may affect your heart

In some people with heart disease, mental stress can curtail blood flow to the heart, boosting the risk of a heart attack.

illustration of a human heart with emphasis on the smallest blood vessels

If you’re suddenly thrust into a stressful, anxiety-provoking situation, your heart may speed up and your blood pressure may rise. But if you have heart disease, emotional stress may also hinder blood flow to parts of your heart. This phenomenon, called mental stress ischemia, may more than double the risk of a heart attack, according to a new study (see "Mental stress and the heart: A closer look").

The study — the largest and most diverse of its kind to date — helps illuminate the connection between stress and heart disease, which was first described over a century ago. "The findings clearly show that mental stress ischemia is an important health problem," says Dr. Ahmed Tawakol, director of nuclear cardiology and co-director of the cardiovascular imaging research center at Harvard-affiliated Massachusetts General Hospital.

The fact that this study includes a sizable number of women is important, he adds. Mental stress ischemia appears to be caused in part by changes in the wall and inner lining of the heart’s smallest blood vessels. Known as microvascular disease, this problem tends to be more prevalent in women than in men. (However, narrowing of the large arteries of the heart is a more common cause of chest pain in both women and men.)

Mental stress and the heart: A closer look

Emotional or mental stress triggers physical changes throughout the body, and the heart is no exception. About one in six people with heart disease experiences decreased blood flow to the heart (ischemia) at times of mental stress. But does mental stress ischemia raise the risk of heart attacks and related problems? A study published Nov. 9, 2021, in JAMA explored this question.

Who: 918 people with heart disease with an average age of 60. About one-third were women and 40% were Black.

How: All participants underwent two separate tests to see how stress — physical and mental — affected blood flow to the heart. For most, the physical test was a conventional exercise stress test done on a treadmill; about 30% instead received a medication to stress the heart. For the mental stress test, participants were given a topic and had two minutes to prepare a three-minute speech to deliver to an audience of at least four people.

What: About one-third of the participants had ischemia on the exercise stress test, while 16% experienced ischemia during mental stress. Ten percent had ischemia during both tests.

When: Over the following five to six years, researchers tracked participants’ rates of heart attacks, heart failure hospitalizations, and death from cardiovascular disease.

Key findings: Compared with people with no ischemia, those with mental stress ischemia were twice as likely to have a heart attack or heart failure during the follow up period. Those with both physical and mental stress ischemia had four times the risk. The risk increased only slightly among people with just physical ischemia.

Understanding microvascular disease

Picture the blood supply to the heart as a tree, where the large blood vessels on the heart’s surface are the tree trunk and major branches, Dr. Tawakol says. As they dive into the heart, the large vessels branch into smaller and smaller arteries. The heart’s tiniest vessels (microvasculature) are like the tree’s twigs or even the veins on a leaf, with the leaves representing areas of heart muscle.

"If you look up into a tree and see disease in one of the large limbs, the leaves at the end of that branch will be affected," explains Dr. Tawakol. "But you might also see disease in the vessels of a leaf — and that leaf will still be affected, even if the large, supporting branch looks okay."

In some people with heart disease, both the larger and smaller arteries are diseased or dysfunctional. They might experience chest pain during exercise as well as during mental stress. Earlier studies have shown that people with both microvascular disease and narrowing of the coronary arteries face the highest risk of future heart problems, says Dr. Tawakol. In this study as well, those with the highest risk were the people who had both mental stress ischemia as well as exercise-induced ischemia.

Unanswered questions

While this study sheds light on how mental stress affects the heart, many questions remain. For example, would it be helpful to screen people for mental stress ischemia? Advanced heart imaging tests are now making it easier to detect subtle changes in blood flow throughout the heart and can detect microvascular disease as well as narrowing of the large coronary arteries. Such tools could potentially further our understanding, Dr. Tawakol says. But a more important question is whether people can do anything to blunt the negative effects of mental stress on their hearts.

To find out, he and colleagues are conducting a study in which volunteers (with and without heart disease) will follow an eight-week Stress Management and Resilience Training (SMART) program. Developed at the Benson-Henry Institute for Mind Body Medicine at Massachusetts General Hospital, the program teaches people self-care practices to better manage stress. A central focus involves learning to evoke the relaxation response — a simple, mind-calming practice that counteracts the body’s response to stress.

Participants will undergo specialized brain and heart imaging tests before and after the training. "We suspect the training will tilt the balance to cause less sympathetic nervous system activity — the fight-or-flight response — in response to stressful events," says Dr. Tawakol. That, in turn, may reduce inflammation and other harmful effects of stress on all parts of the cardiovascular system, all the way down to the tiniest vessels.

Results from the study aren’t expected for at least several years. But other than a small time investment, there are no downsides to practicing stress-busting techniques on your own. The Harvard Special Health Report Stress Management (/sc) provides details and advice.