When Most People Think of a Heart Attack, They Recognize Chest Pain, Shortness of Breath, Fatigue and Sweating as Possible Symptoms
But there is another cardiac condition that occurs on a deeper level that has similar symptoms. Interventional Cardiologist William Suh, MD, explains what Coronary Microvascular Dysfunction (CMD) is, how they test for it, and the treatment options available.
What is Coronary Microvascular Dysfunction (CMD)?
CMD represents a distinct form of heart disease that has been underdiagnosed and undertreated. Newer imaging technologies and physiology tests have enabled cardiologists to make a CMD diagnosis and initiate appropriate treatment.
CMD is a condition where the small blood vessels that supply blood to the heart muscle (myocardium) are affected, leading to impaired blood flow regulation. Unlike traditional coronary artery disease (CAD), which affects the larger epicardial coronary arteries, CMD involves dysfunction in the tiny arterioles and capillaries within the heart muscle which are too small to see on coronary angiography.
Two of the key features of coronary microvascular dysfunction include trouble with the endothelial cells that line the small blood vessels, and increased resistance to blood flow. Dr. Suh explains that the endothelium normally helps regulate blood flow by releasing substances that promote widening and narrowing of the blood vessels. When there is an issue with the endothelium, it can lead to problems with blood flow and can result in lower oxygen delivery to the heart muscle.
What causes CMD?
The causes and risk factors are similar to traditional coronary artery disease, and can include:
- Diabetes - High blood sugar levels can damage blood vessels and impair endothelial function.
- Hypertension - Elevated blood pressure can cause structural changes in blood vessels and affect their ability to dilate and contract.
- Obesity - Excess body weight can lead to metabolic changes that affect vascular function.
- High cholesterol - Elevated cholesterol levels can contribute to atherosclerosis and affect blood vessel function.
- Smoking - Tobacco smoke contains chemicals that damage blood vessels and impair endothelial function.
- Age and Gender - CMD is more common in older individuals and disproportionately affects women, especially after menopause, though it can also occur in men. Women with CMD may experience different symptoms than men, which can make diagnosis and treatment more difficult. Women with CMD may also have a worse prognosis than men, with higher rates of adverse cardiovascular events such as heart attack, stroke, heart failure, and death.
- Microvascular Structural Changes - Structural abnormalities, such as thickening of vessel walls or reduced density of capillaries, can impair blood flow regulation.
- Inflammation - Chronic inflammation, which can occur due to conditions like diabetes, hypertension, or autoimmune disorders, can damage the endothelial cells and affect their function. Inflammatory processes can also lead to atherosclerosis (hardening and narrowing of arteries), which may affect the larger coronary arteries and indirectly impact microvascular function.
- Hormonal Factors - Changes in hormone levels, such as estrogen levels in women after menopause, can influence endothelial function and contribute to CMD.
What are the symptoms of CMD?
Coronary microvascular dysfunction (CMD) can present with symptoms similar to those of traditional coronary artery disease (CAD), but it differs in the underlying mechanisms involved. The small arteries are not able to deliver enough oxygen to the heart muscle in CMD. Common symptoms of CMD include:
- Chest Pain (Angina) - Angina in CMD typically occurs during physical exertion or stress (stable angina), but it can also occur at rest (unstable angina). The chest pain is often described as pressure, squeezing, heaviness, or tightness in the chest. It may radiate to the neck, jaw, shoulders, arms, or back.
- Shortness of Breath - Difficulty breathing or shortness of breath may occur, especially during exertion or when experiencing angina.
- Fatigue - Persistent tiredness or fatigue, even with normal activities, can be a symptom of CMD.
- Other Symptoms - Nausea, dizziness, sweating.
The symptoms can vary in severity and frequency from person to person. Prompt diagnosis and appropriate management are crucial to alleviate symptoms, improve quality of life, and reduce the risk of complications.
How does a doctor test for CMD?
Diagnosing CMD involves a comprehensive evaluation that includes assessing symptoms, risk factors, and performing specialized tests to directly evaluate microvascular function. Recently, Corona Regional Medical Center has started testing for coronary microvascular dysfunction (CMD) in the cardiac catheterization laboratory. Using Abbott’s Coroventis CoroFlow system and the PressureWire™ X Guidewire, cardiologists at CRMC are now able to measure certain factors in the heart. This comprehensive coronary physiology assessment allows the cardiologist to make the diagnosis of CMD and initiate an individualized treatment plan targeted to treat CMD and its risk factors.
Clinical Assessment
A thorough medical history is taken to identify symptoms such as chest pain (angina), shortness of breath, and fatigue, which may suggest CMD. Risk factors for cardiovascular disease, such as diabetes, hypertension, obesity, and smoking, are assessed.
Physical examination, diagnostic tests
A physical examination may reveal signs of cardiovascular disease or other related conditions. The doctor may choose to runs tests such as:
- Electrocardiogram (ECG) - An ECG is performed to detect any abnormalities in heart rhythm or to check for evidence of previous heart damage.
- Echocardiogram - Ultrasound exam of the heart evaluates the structure and function of the heart, including assessing for any abnormalities in heart muscle thickness or function.
- Stress Testing - Exercise or pharmacologic stress testing is conducted to provoke symptoms of angina and assess the heart's response to stress.
- Coronary Angiography or Computed Tomography Coronary Angiography - Angiography visualizes the larger coronary arteries. While it may not show significant blockages in CMD, it can help rule out obstructive coronary artery disease (CAD) in the epicardial coronary arteries.
Specialized Tests for Microvascular Function
- Coronary Reactivity Testing (CRT) - This involves administering medications directly into the coronary arteries to assess how well the small blood vessels (microvasculature) respond. CRT can evaluate endothelial function and measure microvascular spasm.
- Coronary Flow Reserve (CFR) Measurement - CFR assesses the ability of the coronary arteries to increase blood flow in response to increased demand. It provides a quantitative measure of microvascular function.
- Cardiac PET Stress Test - Advanced imaging techniques can assess myocardial perfusion and detect abnormalities in blood flow within the heart muscle. However, this test is not widely available.
What types of treatments are available for CMD?
Treatment of coronary microvascular dysfunction typically focuses on managing symptoms and addressing underlying risk factors. Medications can include the following:
- Nitroglycerin - Helps dilate blood vessels and improve blood flow.
- Calcium channel blockers - Can relax blood vessels and reduce chest pain (angina).
- Beta blockers - These medications may be used to lower heart rate and reduce angina by decreasing oxygen demand of the heart.
- Statins - Used to manage cholesterol levels, which can benefit overall heart health.
Your doctor may also recommend lifestyle changes, such as:
- Healthy diet - Low in saturated fats, cholesterol, and sodium; high in fruits, vegetables, and whole grains.
- Regular exercise - Helps improve cardiovascular fitness and overall heart function.
- Smoking cessation - Important for reducing vascular damage and inflammation.
- Weight management - Maintaining a healthy weight reduces strain on the heart.
If you have other health conditions, your doctor can advise on how to manage them as well. Some of those conditions include:
- Hypertension - Control blood pressure through lifestyle changes and medications.
- Diabetes - Maintain optimal blood sugar levels through diet, exercise, and medications if necessary.
- Hyperlipidemia - Manage cholesterol levels through diet, exercise, and medications.
- Stress management - Monitoring and managing stress, which can exacerbate symptoms.
- Cardiac rehabilitation - Structured programs that include exercise training, education, and counseling to improve heart health.
It's important to note that the treatment approach can vary depending on the individual's specific symptoms, underlying conditions, and overall health status. Therefore, a cardiologist or healthcare provider will tailor the treatment plan accordingly.