In men with coronary artery disease (CAD) the large arteries feeding the heart often become clogged by plaque and this can be seen on coronary angiograms. However, women often have chest pain that is related to reduced levels of oxygen reaching the heart when there is no evidence of any arterial obstruction. It is believed that this is the result of coronary microvascular dysfunction where the tiny coronary artery blood vessels that branch off from the larger coronary arteries do not function properly. This type of coronary artery dysfunction occurs more frequently in women than men although it is not known what causes it.
Now researchers have found that emotional stress may cause changes in the nervous system that can trigger this type of coronary artery dysfunction.
The research was led by Professor C. Noel Bairey Merz, the Medical Director of the Barbra Streisand Women's Heart Centre, at the Cedars-Sinai Heart Institute. She said, "Women who go to emergency rooms and cardiologists because they have chest pain often are told that their arteries are clear and their hearts are fine. But the reality is that women's coronary artery disease tends to be different from men's. In women, the large arteries may remain clear but the smaller branches that connect to the even-smaller capillaries lose their ability to widen. Whether the large arteries are blocked or the small arterioles don't function correctly, the result is the same - the heart becomes starved for oxygen.”
Professor Bairey Merz chairs the Women's Ischemic Syndrome Evaluation study, known as WISE, which began in 1997 and is sponsored by the National Heart, Lung, and Blood Institute, and which has brought to light gender-related differences in heart disease.
Dr Puja K. Mehta who was part of the research team said, “We know that women who have chest pain and reduced oxygen to the heart, in the absence of 'male-pattern' obstructive coronary artery disease, may experience microvascular dysfunction during times of emotional distress even though their heart rates stay relatively low. In this study, we evaluated the heart's autonomic system, the nerve network that regulates heart rate.”
Sixteen women diagnosed with coronary microvascular dysfunction participated, as did eight women of similar age and weight who did not have coronary microvascular dysfunction. Heart rate, blood pressure and heart rate variability were measured when the women were at rest and again when they were subjected to several types of mental stress.
Both groups responded in the same way to the stressors, except when dealing with the emotional stress of anger. In women with microvascular dysfunction, emotional stress appeared to increase sympathetic nerve stimulation, which is associated with the quickened heart rate of the fight or flight mechanism, and decreased parasympathetic nerve activity, which relaxes and slows heart rate.
Dr Mehta said these results suggest that the autonomic nervous system may be one pathway involved in microvascular dysfunction in women.
"More specifically, we hypothesise that emotional stress may trigger microvascular dysfunction and lead to heart attacks and other cardiac problems in women," she said, adding that more research is needed to better understand this mechanism and identify others that might exist.
The findings were presented at the American Psychosomatic Society's annual meeting in San Francisco.
