Women and Coronary Microvascular Dysfunction (CMD)

Women of all ages, especially younger women, are more likely than men to develop a type of heart disease called coronary microvascular dysfunction (CMD).

Go Red for Women national volunteer Dr. Harmony Reynolds, director of the Sarah Ross Soter Center for Women’s Cardiovascular Research at NYU Langone Health, helps answer some common questions about coronary microvascular dysfunction and women’s health.

What is coronary microvascular dysfunction and are there symptoms women should talk to their doctor about?

Coronary microvascular dysfunction is a problem of the small arteries of the heart with reduced blood flow without any accompanying large vessel obstructive disease. In people with coronary microvascular dysfunction, the heart doesn't receive as much blood as it needs to do its job well.

Patients can sense this as discomfort or pain in the chest, or in another area of the upper body, or as shortness of breath or fatigue.

Coronary microvascular dysfunction is one of two main reasons for heart symptoms when the arteries are not badly blocked. The umbrella term for these problems is INOCA, or ischemia with no obstructed coronary arteries. The other common reason for INOCA is coronary artery spasm, in which the muscle layer normally present in arteries becomes overreactive and can temporarily narrow or close the artery, leading to symptoms or even a heart attack.

If you are experiencing symptoms or discomfort, don’t wait, alert your health care team.

Is coronary microvascular dysfunction the same as syndrome X?

Cardiac syndrome X is an older term for INOCA. We don’t use that term these days because it suggests that we don’t know what is causing the problem. In fact, we've learned much about the syndrome over years of research.

Why are women at higher risk for developing CMD?

We don’t know exactly why. As an example, our research group recently showed in a group of patients with moderately or severely abnormal stress tests that 66% of those with no major artery blockage (INOCA) were female, but only 26% of patients who had a major blockage (coronary artery disease) were female. Finding out why women are more likely to have this problem will be an important ongoing area of research.

How is CMD diagnosed and treated?

The most accurate way of making the diagnosis is to do additional invasive testing at the time of a coronary angiogram. In this type of testing, measurements are made of the flow and resistance to flow in the heart. This is called coronary reactivity testing or invasive diagnostic testing. Another way of making the diagnosis is to do non-invasive testing such as a PET scan or cardiac MRI to check blood flow.

During invasive coronary reactivity testing, it's also possible to find out whether someone has coronary artery spasm. In the absence of this sort of testing, doctors may strongly suspect CMD when patients have an abnormal stress test and symptoms but do not have any major blockage on either a conventional invasive coronary angiogram or a CT (noninvasive) coronary angiogram.

Doctors may suspect coronary artery spasm when chest discomfort or other symptoms follow a certain pattern — for example, if a patient is awakened from sleep and the symptoms get better quickly with nitroglycerin treatment.

While no medications are currently specifically indicated for CMD, the disease is treated with medications typically used for angina (heart pain). These medications work to rebalance the heart’s demands for blood flow and the supply of blood. The medications include beta blockers, nitroglycerin and related drugs, calcium channel blockers and others. ACE inhibitors may offer benefit for symptom relief as well. Weight loss and exercise can make a big impact on symptoms.

What else can women do to prevent or reduce the risk of developing CMD?

We know that patients who have other cardiovascular risk factors like hypertension, diabetes and obesity may be at higher risk of developing CMD. Healthy diet and exercise are always an important part of heart disease prevention, and treatment for high blood pressure and diabetes may be helpful as well.

What more can be done to help us better understand CMD in women?

We've learned a great deal about CMD in recent years, but there is so much more to learn, such as:

• Why exactly are women at higher risk?
• What is the best method of diagnosis?
• Should invasive reactivity testing be part of every cardiac catheterization for women with stable heart symptoms?
• Which treatments are best for symptom relief, and which treatments reduce the risk of future events like heart attack, stroke or heart failure?

Research on these and other questions related to CMD will be important to improving our understanding of this common problem.