Blockages in tiny heart arteries a big problem for women

Lloyd Resnick

Former Editor, Harvard Heart Letter

About 10% of women who have a heart attack seem to have clear, unblocked arteries. So what’s behind the cutoff in blood flow (ischemia) that causes their attacks?

In many cases, the culprit is microvascular disease, says Dr. C. Noel Bairey Merz from Cedars-Sinai Medical Center in Los Angles. Microvascular disease refers to narrowings of tiny arteries supplying the heart muscle that are too small to show up on traditional diagnostic tests. Dr. Bairey Merz, the principal investigator for the Women’s Ischemia Syndrome Evaluation (WISE) study, presented a summary of WISE findings to cardiologists at Harvard Medical School, her medical alma mater.

What triggers microvascular disease isn’t known, but Dr. Bairey Merz suggested that high blood pressure during pregnancy might predispose some women to the condition. Typically, the narrowings are caused by fatty plaque, the same stuff that clogs bigger vessels, where most heart attacks begin. But in microvascular disease, plaque doesn’t form a mound or bulge. Instead, it uniformly coats the inside of the vessels. This reduces the space for blood flow and makes the arteries stiff and less able to expand in response to exercise or other stress.

The gold standard for detecting microvascular disease is currently coronary reactivity testing. This angiogram-like test lasts 60 to 90 minutes and allows doctors to see how very small vessels supplying the heart respond to different “challenges” from medications. Showing slides of tiny vessels that narrowed in response to a certain drug when they should have widened, Dr. Bairey Merz emphasized that microvascular disease is not a benign condition, as previously thought. “This is real ischemia,” she said.

Women with confirmed microvascular disease may be candidates for medical treatment. One possible treatment being explored is the erectile dysfunction drug Viagra (sildenafil), which was originally developed to improve blood flow to the heart. ACE inhibitors, beta blockers, and statins might also help reduce chest pain from microvascular disease and improve small blood vessel function. But it’s too early to tell which if any medication will reduce the number of heart attacks in women arising from microvascular disease, said Dr. Bairey Merz.


  1. Rose Atkin

    I wonder if hormonal changes also part of the reason of microvascular disease,since it is unique to women only .I always hear docs says once estrogen hormone is gone due to menapause ,women are more prone to MI .

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