What Is Coronary Microvascular Disease?

Coronary microvascular disease (MVD) affects the heart's smallest coronary arteries. Coronary MVD occurs in the heart's tiny arteries when:

• Plaque (plak) forms in the arteries. Plaque is made up of fat, cholesterol (ko-LES-ter-ol), calcium, and other substances found in the blood. It narrows the coronary arteries and reduces blood flow to the heart muscle. As a result, the heart doesn't get the oxygen it needs. This is known as ischemic (is-KE-mik) heart disease, or heart disease. In coronary MVD, plaque can scatter, spread out evenly, or build up into blockages in the tiny coronary arteries.
• The arteries spasm (tighten). Spasms of the small coronary arteries also can prevent enough oxygen-rich blood from moving through the arteries. This too can cause ischemic heart disease.
• The walls of the arteries are damaged or diseased. Changes in the arteries' cells and the surrounding muscle tissues may, over time, damage the arteries' walls.

Coronary MVD is a new concept. It's different from traditional coronary artery disease (CAD). In CAD, plaque builds up in the heart's large arteries. This buildup can lead to blockages that limit or prevent oxygen-rich blood from reaching the heart muscle.

In coronary MVD, however, the heart's smallest arteries are affected. Plaque doesn't always create blockages as it does in CAD. For this reason, coronary MVD also is called nonobstructive CAD.

No one knows whether coronary MVD is the same as MVD linked to other diseases, such as diabetes.

Overview

Death rates from heart disease have dropped quite a bit in the last 30 years. This is due to improved treatments for conditions such as blocked coronary arteries, heart attack, and heart failure.

However, death rates haven't improved as much in women as they have in men. Heart disease in men and women may differ. Many researchers think that a drop in estrogen levels in women at menopause combined with traditional risk factors for heart disease causes coronary MVD. Therefore, coronary MVD is being studied as a possible cause of heart disease in women.

Diagnosing coronary MVD has been a challenge for doctors. Most of the research on heart disease has been done on men.

Standard tests used to diagnose heart disease have been useful in finding blockages in the coronary arteries. However, these same tests used in women with symptoms of heart disease—such as chest pain—often show that they have "clear" arteries.

This is because standard tests for CAD don't always detect coronary MVD in women. Standard tests look for blockages that affect blood flow in the large coronary arteries. However, these tests can't detect plaque that forms, scatters, or builds up in the smallest coronary arteries.

The standard tests also can't detect when the arteries spasm (tighten) or when the walls of the arteries are damaged or diseased.

As a result, women are often thought to be at low risk for heart disease.

Outlook

Coronary MVD is thought to affect up to 3 million women with heart disease in the United States.

Most of the information known about coronary MVD comes from the National Heart, Lung, and Blood Institute's WISE study (Women's Ischemia Syndrome Evaluation). The WISE study began in 1996. Its goal was to learn more about how heart disease develops in women.

The role of hormones in heart disease has been studied, as well as how to improve the diagnosis of coronary MVD. Further studies are under way to learn more about the disease, how to treat it, and its outcomes.

What Causes Coronary Microvascular Disease?

The same cluster of risk factors that causes atherosclerosis (ATH-er-o-skler-O-sis) may cause coronary microvascular disease (MVD) in women. Atherosclerosis is when the arteries harden and narrow due to the buildup plaque on their inner walls. It's one of the key causes of heart disease.

Risk factors for atherosclerosis include:

• Unhealthy cholesterol levels. This includes high LDL cholesterol (sometimes called bad cholesterol), low HDL cholesterol (sometimes called good cholesterol), and high triglyerides (another type of fat in the blood).
• High blood pressure. Blood pressure is considered high if it stays at or above 140/90 mmHg over a period of time.
• Smoking. This can damage and tighten blood vessels, increase cholesterol levels, and increase blood pressure. Smoking also doesn't allow enough oxygen to reach the body's tissues.
• Insulin resistance. This condition occurs when the body can't use its own insulin properly. Insulin is a hormone that helps the body convert food to energy.
• Diabetes. This is a disease in which the body's blood sugar level is high because the body doesn't make enough insulin or doesn't use its insulin properly.
• Overweight or obesity. Overweight is having extra body weight from muscle, bone, fat, and/or water. Obesity is having a high amount of extra body fat.
• Lack of physical activity. Lack of activity can worsen other risk factors for atherosclerosis.
• Age. As you get older, your risk for atherosclerosis increases. Genetic or lifestyle factors cause plaque to build in arteries as you age. By the time you are middle-aged or older, enough plaque has built up to cause signs or symptoms.
  • In men, the risk increases after age 45.
  • In women, the risk increases after age 55.
• Family history of early heart disease. Your risk for atherosclerosis increases if your father or a brother was diagnosed with heart disease before 55 years of age, or if your mother or a sister was diagnosed with heart disease before 65 years of age.

Coronary MVD may be linked to low estrogen levels occurring before or after menopause. It also may be linked to anemia or conditions that affect blood clotting. Anemia is thought to slow the growth of cells needed to repair damaged blood vessels.

It's not yet known whether coronary MVD is the same as MVD linked to other diseases, such as diabetes.

Who Is At Risk for Coronary Microvascular Disease?

Women at high risk for coronary microvascular disease (MVD) often have multiple risk factors for atherosclerosis. (See "What Causes Coronary Microvascular Disease?" for a detailed list of these risk factors.)

Women may be at risk for coronary MVD if they have low levels of estrogen at any point in their adult lives. (This refers to the estrogen that the ovaries produce, not the estrogen used in hormone replacement therapy.)

• After menopause, women tend to have more of the traditional risk factors for atherosclerosis, putting them at higher risk for coronary MVD.
• Lower than normal estrogen levels in women before menopause also can put younger women at higher risk for coronary MVD. One cause of low estrogen levels in younger women is mental stress. Another is a problem with the function of the ovaries.

Women who have high blood pressure before menopause, especially high systolic blood pressure, are at higher risk for coronary MVD. (Systolic blood pressure is the top or first number of a blood pressure measurement).

Women with heart disease have an increased risk for a worse outcome, such as a heart attack, if they also have anemia. Anemia is thought to slow the growth of cells needed to repair damaged blood vessels.

What Are the Signs and Symptoms of Coronary Microvascular Disease?

Signs and symptoms of coronary microvascular disease (MVD) often differ from signs and symptoms of traditional coronary artery disease (CAD).

Many women with coronary MVD have angina (chest pain), but it may or may not be the "typical" chest pain seen in CAD. Typical signs and symptoms of CAD include angina, feeling pressure or squeezing in the chest, shortness of breath, heavy sweating, and arm or shoulder pain.

These signs and symptoms often first appear while a person is being physically active—such as while jogging, walking on a treadmill, or going up stairs. Typical angina is more frequent in women older than 65.

Other signs and symptoms of coronary MVD in women are shortness of breath, sleep problems, fatigue (tiredness), and lack of energy.

In women, coronary MVD symptoms are often first noticed during routine daily activities (such as shopping, cooking, cleaning, and going to work) and during times of mental stress. It's less likely that women will notice these symptoms during physical activity (such as jogging or walking fast).

How Is Coronary Microvascular Disease Diagnosed?

First, your doctor will take your medical history and do a physical exam to diagnose coronary microvascular disease (MVD). The doctor will check to see if you have any risk factors for heart disease. You will be weighed to check for obesity, and your cholesterol will be tested. You also will be tested for metabolic syndrome and diabetes.

Your doctor may ask you to describe any chest pain, including when it started and how it changed during physical activity or periods of stress.

Other symptoms such as fatigue (tiredness), lack of energy, and shortness of breath will be noted. Women will be asked about their menopausal status. Your doctor may order blood tests, including a test for anemia.

Specialists Involved

Doctors who diagnose and treat coronary MVD are most often specialists in cardiology (heart disease), family medicine, and internal medicine.

Diagnostic Tests

The risk factors for traditional coronary artery disease (CAD) and coronary MVD are often the same. Therefore, your doctor will use tests to help show if you have traditional CAD. These tests may include:

• Coronary angiography (an-jee-OG-ra-fee). This test is a special x-ray exam of the heart and blood vessels. It shows plaque buildup in the large coronary arteries. This test is often done during a heart attack to help locate blockages.
• A stress test. This test provides your doctor with information about blood flow through the coronary arteries to your heart muscle during physical stress. During stress testing, you exercise (or are given medicine if you're unable to exercise) to make your heart work hard and beat fast while heart tests, such as nuclear heart scanning and echocardiography, are performed. If coronary angiography doesn't show plaque buildup in the large coronary arteries, a stress test may still show abnormal blood flow. This may be a sign of coronary MVD.
• A magnetic resonance imaging (MRI) cardiac stress test. This test is being used more widely to evaluate women with chest pain.

Unfortunately, standard tests for CAD don't always detect heart disease in women. Standard tests look for blockages that affect blood flow in the large coronary arteries. However, the WISE Study showed that, in women, damage to the heart's smallest coronary arteries may affect blood flow.

This damage occurs when plaque forms in arteries, when the arteries spasm (tighten), or when the walls of the arteries are damaged or diseased.

In coronary MVD, plaque can scatter, spread out evenly, or build up into blockages in the tiny coronary arteries. Plaque narrows the coronary arteries and reduces blood flow to the heart muscle.

Spasms of the small coronary arteries prevent enough oxygen-rich blood from moving through the arteries.

Changes in the arteries' cells and the surrounding muscle tissues may, over time, damage the arteries' walls.

The standard tests for CAD can't detect these types of problems in the tiny coronary arteries. Therefore, standard tests may show that a woman doesn't have heart disease, even if she does. (Fifty percent of women who have the standard CAD tests show normal coronary arteries compared to 17 percent of men.)

If test results show you don't have CAD, you can still be diagnosed with coronary MVD if evidence shows that not enough oxygen is reaching the small arteries in your heart.

Since symptoms of coronary MVD often first appear during routine daily tasks, you may be asked to fill out a questionnaire called the Duke Activity Status Index (DASI). The questionnaire will ask you how well you're able to do daily activities such as shopping, cooking, and going to work. The results of this survey will help doctors decide on the kind of stress test you should have. It will also give them some information about how well the blood is flowing through your coronary arteries.

Research continues to improve ways to detect and diagnose heart disease caused by coronary MVD.

How Is Coronary Microvascular Disease Treated?

Women who have coronary microvascular disease (MVD) are mainly treated to control their risk factors for heart disease and symptoms. Treatments may include medicines such as:

• Statins to improve cholesterol levels
• Angiotensin-converting enzyme (ACE) inhibitors and beta blockers to lower blood pressure and decrease the heart's workload
• Aspirin to help prevent blood clots or control inflammation
• Nitroglycerin to relax blood vessels, improve blood flow to the heart muscle, and treat chest pain (if this medicine has helped the patient with past symptoms)

Women diagnosed with coronary MVD who also have anemia may benefit from treatment for that condition, because anemia slows repair of damaged blood vessels.

Women who are diagnosed and treated for coronary MVD should be checked regularly by their doctors.

Research is ongoing to find the best treatments for coronary MVD.

How Can Coronary Microvascular Disease Be Prevented?

No specific studies have been done on how to prevent coronary microvascular disease (MVD). It's not yet known how or in what way preventing the condition differs from preventing coronary artery disease (CAD). Coronary MVD affects the small coronary arteries in the heart, while CAD affects the large coronary arteries.

You can prevent or delay CAD by taking action to reduce your risk factors. You can't control some risk factors such as age and family history of heart disease. However, you can take steps to lower or control other risk factors such as high blood pressure, overweight and obesity, high blood cholesterol, diabetes, and smoking.

Regardless of your age or family history, you can lower your risk of heart disease with lifestyle changes. These changes include:

• Following a heart healthy eating plan. Two heart healthy eating plans are the Dietary Approaches to Stop Hypertension (DASH) diet (for people who have high blood pressure) and the Therapeutic Lifestyle Changes (TLC) diet (for people who have high blood cholesterol).
• Increasing your physical activity. Aim for at least 30 minutes of moderate-intensity activity on most, and preferably, all days of the week. If you're trying to manage your weight and keep from gaining weight, try to get 60 minutes of moderate-to-vigorous-intensity physical activity on most days of the week.
• Quitting smoking, if you smoke.
• Losing weight, if you're overweight.
• Reducing your stress level.

It's also important to learn more about heart disease and the kinds of habits and conditions that can increase your risk.

• Talk to your doctor about your risk factors for heart disease and how to control them.
• Know your numbers—ask your doctor for these three tests and have the results explained to you.
  • Lipid profile. This test measures total cholesterol, LDL cholesterol (sometimes called bad cholesterol), HDL cholesterol (sometimes called good cholesterol), and triglycerides (another form of fat in the blood).
  • Blood pressure.
  • Fasting blood glucose. This test is for diabetes.
• Know your body mass index (BMI) and waist circumference. BMI is an estimate of body fat that's calculated from your height and weight. You can use the National Heart, Lung, and Blood Institute's online BMI calculator to figure out your BMI. To measure your waistline, stand and place a tape measure around your middle, just above your hipbones. Measure your waist just after you breathe out.
• Take medicines for lowering cholesterol and blood pressure and controlling diabetes as your doctor prescribes.

Living With Coronary Microvascular Disease

If you have coronary microvascular disease (MVD), you can take steps to stop it from getting worse. These steps are the same as those used to prevent coronary MVD. See "How Can Coronary Microvascular Disease Be Prevented" for more information.

If you have coronary MVD, see your doctor regularly to make sure the disease isn't getting worse and to keep track of your cholesterol, blood pressure, and blood sugar levels. A cholesterol blood test will show your levels of LDL cholesterol, HDL cholesterol, and triglycerides. It will show whether you need more treatment. You may need to see a cardiologist in addition to your primary care doctor.

Talk to your doctor about how often you should schedule office visits or blood tests. Between those visits, call your doctor if you develop any new symptoms or your symptoms become more severe. You should:

• Know your symptoms and how and when to seek medical help.
• Be able to describe the usual pattern of your symptoms.
• Know which medicines you take and when and how to take them.
• Know how to control your symptoms, including angina.
• Know the limits of your physical activity.
• Learn ways to avoid or cope with stress.

MVD, like traditional coronary artery disease, increases your chance for a heart attack. Signs and symptoms of a heart attack include:

• Chest discomfort or pain—uncomfortable pressure, squeezing, fullness, or pain in the center of the chest that can be mild or strong. This discomfort or pain lasts more than a few minutes or goes away and comes back.
• Upper body discomfort in one or both arms, the back, neck, jaw, or stomach.
• Shortness of breath that may occur with or before chest discomfort.
• Other signs include nausea (feeling sick to your stomach), vomiting, lightheadedness or fainting, or breaking out in a cold sweat.

Call 9–1–1 within 5 minutes if you think you're having a heart attack. Acting fast at the first sign of heart attack symptoms can save your life and limit damage to your heart. Treatment is most effective when started within 1 hour of the beginning of symptoms.

Key Points

• Coronary microvascular disease (MVD) affects the heart's smallest coronary arteries. Coronary MVD occurs when plaque forms in the arteries, when the arteries spasm (tighten), or when the walls of the arteries are diseased or damaged.
• In coronary MVD, plaque can scatter, spread out evenly, or build up into blockages in the small coronary arteries. Plaque reduces the flow of oxygen-rich blood to the heart muscle. Spasms also prevent enough oxygen-rich blood from getting to the heart muscle. Changes in the arteries' cells and the surrounding muscle tissues may, over time, damage the arteries' walls.
• In coronary MVD, plaque doesn't always lead to blockages as it does in traditional coronary artery disease (CAD). For this reason, coronary MVD is called nonobstructive CAD.
• Coronary MVD is a new concept. It's currently being studied as a possible cause of heart disease in women. Many researchers think that a drop in estrogen levels in women at menopause combined with risk factors for heart disease causes coronary MVD.
• No one knows whether coronary MVD is the same as MVD linked to other diseases, such as diabetes.
• The same cluster of risk factors that cause atherosclerosis and CAD may cause coronary MVD. These include unhealthy cholesterol levels, high blood pressure, smoking, insulin resistance, diabetes, overweight and obesity, lack of physical activity, age, and family history of early heart disease.
• Coronary MVD in women may be linked to low estrogen levels occurring before or after menopause. It also may be linked to anemia or conditions that affect blood clotting.
• Signs and symptoms of coronary MVD often differ from those of traditional CAD. Typical signs and symptoms of CAD include angina (chest pain), feeling pressure or squeezing in the chest, shortness of breath, excessive sweating, and arm or shoulder pain. Many women with coronary MVD have angina, but it may not by "typical."
• Women with coronary MVD may also have shortness of breath, sleep problems, fatigue (tiredness), and lack of energy. In women, symptoms are often first noticed during routine daily activities and times of mental stress.
• Medical history and a physical exam are used to diagnose coronary MVD. Your doctor may also give you tests for traditional CAD. These may include coronary angiography, stress testing, and magnetic resonance imaging cardiac stress testing. You also may be asked to fill out a questionnaire called the Duke Activity Status Index, which measures how well you're able to do your daily activities.
• If test results show you don't have traditional CAD, you can still be diagnosed with coronary MVD if evidence shows that not enough oxygen is reaching the small arteries in your heart.
• Women who have coronary MVD are treated with medicines to control symptoms and risk factors for heart disease. Women diagnosed with coronary MVD who have anemia may benefit from treatment for that condition.
• Women who are diagnosed and treated for coronary MVD should be checked regularly by their doctors.
• No specific studies have yet been done on how to prevent coronary MVD. It's not yet known how or in what way preventing coronary MVD differs from preventing CAD. People can take steps to delay or prevent CAD by making lifestyle changes, taking medicines, and getting regular medical care.
• If you have coronary MVD, you can take steps to stop it from getting worse. These may include lifestyle changes, medicines, and regular medical care.
• If you have symptoms of heart disease, know how and when to seek medical help. Be able to describe your symptoms, and know how to control them. Know which medicines you take and how to take them. Finally, know the limits of your physical activity and how to avoid or cope with stress.
• If you have signs and symptoms of a heart attack, such as chest pain, upper body discomfort, shortness of breath, and nausea, call 9–1–1 right away.

Links to Other Information About Coronary Microvascular Disease

NHLBI Resources

• Coronary Artery Disease (Diseases and Conditions Index)
• "Your Guide to Living Well With Heart Disease"
• "The Healthy Heart Handbook for Women"
• "Your Guide to a Healthy Heart"
• The Heart Truth Campaign

Non-NHLBI Resources

• Coronary Microvascular Disease (MedlinePlus)

Clinical Trials

• Current Research (ClinicalTrials.gov)