When Chest Pain Isn't a Heart Attack: A Look at Coronary Microvascular Dysfunction

Cardiologists are learning more about a condition called coronary microvascular dysfunction (coronary MVD). Previously known as cardiac syndrome X, the condition might be the cause of many unexplained cases of chest pain.

What Is Coronary Microvascular Dysfunction?

Coronary microvascular dysfunction occurs when there is decreased blood flow through the small blood vessels that supply blood flow and oxygen to the heart. Coronary MVD causes chest pain and sometimes shortness of breath and fatigue.

The condition is often a missed diagnosis because blockages in the large arteries in the heart (rather than the small) cause most heart attacks. Coronary MVD is also not always visible with the standard tests for chest pain.

Timothy Henry, MD, an interventional cardiologist with The Christ Hospital in Cincinnati, Ohio, and a leading researcher in coronary MVD, tells Verywell that “the arteries to your heart are like the branches on a tree. You have big branches, and those break down into smaller branches.”

“The microvasculature is incredibly important because most of the blood supply to your heart comes from the little arteries,” Henry says. “When we’re sitting, we need a certain amount of blood flow, but if you exercise, you should increase your blood flow to your heart by about more than three times. When you have coronary microvascular disease, you are not able to increase the flow when you need it, which leads to chest pain.”

Why Does Coronary MVD Mostly Impact Women?

The symptoms of coronary MVD can persist for years without any explanation.

“Some of these individuals have had chest pain for 10 to 15 years,” Henry says. Both men and women can develop microvascular angina, but it’s much more common in women. Among patients with stable chest pain, about 41% of women versus 8% of men show no large artery obstructions on angiograms.

Suzanne Steinbaum, DO, president of SRSHeart and a cardiologist in New York City, tells Verywell that hormones might be part of the reason why coronary MVD is more common in women.

“Microvascular disease happens in the perimenopausal time when there are fluctuations in estrogen,” Steinbaum says. “It’s also associated with the traditional risk factors, especially high blood pressure, high cholesterol and anemia, which often occur with menstruating women [of that age].”

When to See a Doctor

Any person who has recurrent and unexplained chest pain should be evaluated by a cardiologist. Henry says that one test to detect coronary MVD, coronary reactivity testing, “takes 30 minutes and is very low risk.”

During the procedure, a cardiologist inserts a wire with a sensor on the tip through the largest artery of the heart. The sensor measures blood flow to the heart at rest and after a person is given adenosine, a medication that increases the blood flow to the heart.

“A person with normal circulation to the heart will increase blood flow by three times. Less than 2.5 times is abnormal,” Henry says.

Consequences of Untreated Coronary MVD

Untreated coronary MVD restricts blood flow to the heart muscle, and over time, this can lead to irreversible heart damage. “It’s progressive,” Steinbaum says, emphasizing that coronary MVD will not improve unless a person gets treatment. “You have the potential for developing silent heart attacks decades down the line.”

Steinbaum adds that for women especially, education and empowerment are key to preventing heart disease. “Eighty percent of heart disease is preventable,” she says. “It’s about knowing [a woman’s] signs and symptoms and making sure that she gets treated, diagnosed, and taken care of.”

Henry adds that for people with coronary MVD who do not get treatment, “the most common result is heart failure because not having enough blood supply, in the long run, makes your heart stiffer.”

Improving Quality of Life

“[Those with coronary MVD] can’t do the activities that they are accustomed to being able to do. They don’t feel like themselves,” Steinbaum says. “For women who are perimenopausal, this is an age where there is a fluctuation in hormones, and they already don’t feel well.”

Henry says that 90% of people with coronary MVD see an improvement in their symptoms with proper treatment. “We’ve known about microvascular dysfunction for a long time, but our ability to detect it has improved, and we are more aware of it. More frequently, we are developing novel treatments.”

How Is Coronary MVD Managed?

For many individuals, lifestyle modifications and medication can improve their coronary MVD chest pain. “I give everyone exercise prescriptions. It’s the mainstay of what keeps people healthy,” Steinbaum says. “Getting women in a routine of regular exercise and a healthy diet is essential, along with stress management.”

Your provider may also want you to try medication. Drugs used to treat CMD include:

• Nitroglycerin: This drug opens the coronary arteries quickly, providing immediate relief during episodes of chest pain.
• Isosorbide: This is long-acting nitroglycerin taken daily to prevent chest pain.
• Beta-blockers and calcium channel blockers: These drugs decrease the heart’s workload, allowing the muscle to rest and reducing the need for additional blood flow.

Future Treatments

In addition to the mainstays, there are potential advancements in coronary MVD treatment on the horizon. Henry is leading the FREEDOM Trial, which is exploring the use of stem cells to grow new blood vessels in the heart muscle.

The study participants will receive an intravenous drug once a day for five days to stimulate the growth of CD34+ cells, which the bone marrow produces to help develop new blood vessels. Then, the stem cells are removed from the body through a process called apheresis, which separates the patient’s main blood components.

The stem cells are then processed in a specialized laboratory and purified (but they remain unmodified) before being returned to the heart through a small catheter in the wrist or groin.