Problems in the heart’s tiniest arteries can pose challenges for diagnosing and treating chest pain.

The old adage “Out of sight, out of mind” captures a common response to a seemingly mysterious condition — frequent chest pain or other telltale signs of poor blood flow to the heart muscle with “clean” coronary arteries. People with this puzzling combination are often told they are “fine” in spite of symptoms every bit as real, and as debilitating, as those caused by a cholesterol-clogged coronary artery. Some struggle with the problem for years, doubted by their doctors, their symptoms chalked up to depression, anxiety, or even hypochondria.

The large coronary arteries don’t have a monopoly on heart disease. Research is revealing that trouble in the heart’s smallest arteries can cause classic symptoms of heart disease, like chest pain and shortness of breath, along with less well-recognized ones such as diffuse discomfort in the chest or unusual exhaustion.

This condition, called coronary microvascular disease, affects as many as three million American women and an unknown, but probably smaller, number of men.

Peeking into microvessels

Chest pain and other symptoms that the heart muscle isn’t getting enough blood have traditionally signaled a narrowing or blockage in one or more of the heart’s large arteries. Advances in technology that let doctors “see” into the heart’s smallest arteries, called coronary microvessels, are broadening the concept of coronary heart disease.

In some people — women more than men — coronary microvessels stiffen and become unable to relax and dilate. “When microvessels lose their ability to respond to the heart’s changing demands for oxygenated blood, chest pain and other symptoms can follow no matter how clean the larger coronary arteries are,” says Dr. Jane A. Leopold, a cardiologist who directs the Women’s Interventional Cardiology Health Initiative at Harvard-affiliated Brigham and Women’s Hospital.

Microvessel disease

© Harvard

The arteries that actually deliver blood to the heart muscle are too small to be seen on an angiogram.

Detecting microvascular disease

There isn’t yet an easy way to identify coronary microvascular disease. The best test so far, called coronary artery flow reserve or coronary vascular reactivity, requires maneuvering an ultrathin wire with sensors at the tip into a coronary artery. It measures blood flow and pressure before and after infusing into the heart medications that should cause microvessels to dilate. The smaller the change in pressure and flow, the stiffer the microvessels. This test is done only at a small number of cardiac centers in the country.

Researchers are exploring noninvasive ways to detect coronary microvascular disease. One possibility is cardiac magnetic resonance imaging (MRI). It entails making MRI scans before and after infusing the heart with a drug that dilates the tiniest coronary arteries. Another test, called reactive hyperemia peripheral arterial tonometry, uses a sensor placed on a fingertip to gauge blood vessel flexibility.

“You’re fine” isn’t an answer

The concept of coronary microvascular disease hasn’t yet percolated into mainstream medicine. One reason for the slow spread is that “we don’t yet have good tools for diagnosing coronary microvascular disease or know how best to treat it,” says Dr. C. Noel Bairey-Merz, director of the Women’s Heart Center at Cedars-Sinai Medical Center in Los Angeles and a leading researcher in this field. But take heart, she counsels women. The rise of centers devoted to women’s cardiovascular care coupled with intense research into coronary microvascular disease should mean that even community cardiologists will recognize it in a few years.

How best to treat coronary microvascular disease is another gray area. Relieving symptoms is essential. It helps an individual feel better, be more active, and get on with her or his life. It also indicates that the small arteries are open, which is good for the heart’s long-term health. Standard anti-angina drugs that work by relaxing blood vessels, such as nitroglycerin, can help ease symptoms. Beta blockers and calcium-channel blockers work, too, though whether one is better than the other must be hashed out in future studies.

Preventing a heart attack is the other goal of treatment. Key strategies for this include taking low-dose aspirin, aggressively managing blood pressure, cholesterol, and blood sugar levels, and addressing smoking, excess weight, inactivity, and other risk factors.

Although much remains to be learned about coronary microvascular disease, it’s time for doctors to wake up to the fact that heart disease doesn’t always look the same in women and men. Diagnosing it requires careful listening as much as judicious testing. If you have recurrent chest pain and your doctor says you’re fine just because you have clean coronary arteries, seek a second opinion. A doctor affiliated with a women’s cardiovascular care center may be your best bet.

Last Updated: 04/08