Microvascular angina (MVA) is a form of chest pain that occurs when the heart’s smallest blood vessels fail to function correctly. This condition is distinct from traditional angina, which is typically caused by major blockages in the heart’s large arteries. MVA causes significant discomfort and is challenging to diagnose. Understanding the mechanisms, diagnostic challenges, and long-term implications of MVA is the first step toward effective management and risk reduction.
Understanding Microvascular Angina
Microvascular angina arises from a problem within the coronary microvasculature, a complex network of tiny arteries and capillaries embedded within the heart muscle. Dysfunction in this system, often referred to as coronary microvascular dysfunction (CMD), prevents these small vessels from dilating properly when the heart needs more oxygen, such as during exercise or stress.
The inadequate blood flow, or ischemia, is caused by two main mechanisms: the vessels failing to widen or, in some cases, going into spasm and constricting abnormally. Because the problem is diffuse and affects the smallest vessels, the resulting chest pain can feel different from typical angina. The discomfort may be more diffuse, longer-lasting, and often triggered by emotional stress or cold temperatures, not just physical exertion.
Microvascular angina is fundamentally different from obstructive coronary artery disease (CAD), which involves plaque buildup in the large epicardial arteries. People with MVA do not have significant blockages visible on a standard angiogram. Historically, this led to the condition being referred to as Cardiac Syndrome X. This distinction is important because the absence of large blockages often leads to misdiagnosis or the dismissal of symptoms.
Identifying the Condition
Diagnosing microvascular angina presents a challenge because the standard test used to identify most heart disease, the coronary angiogram, appears normal. Since the microvessels are too small to be seen clearly on this imaging, a patient’s chest pain may be mistakenly attributed to non-cardiac causes.
When MVA is suspected, diagnosis requires specialized evaluation focused on measuring the function of the heart’s blood flow reserve. Non-invasive tests include specialized stress testing, such as cardiac Magnetic Resonance Imaging (MRI) or Positron Emission Tomography (PET) scans, which can measure changes in myocardial blood flow under stress. These tests look for evidence of reduced blood flow to the heart muscle.
The most definitive diagnosis often involves an invasive procedure called coronary reactivity testing, usually performed during a cardiac catheterization. This test uses specific medications, like acetylcholine, to check the microvessels’ ability to dilate and assess parameters such as Coronary Flow Reserve (CFR) or the Index of Microcirculatory Resistance (IMR). Measuring these flow dynamics provides objective evidence of microvascular dysfunction, confirming the diagnosis.
Assessing the Danger and Long-Term Outlook
The primary question for many people with this diagnosis is whether microvascular angina is dangerous, and the answer requires distinguishing between acute and long-term risks. MVA is rarely the direct cause of a sudden heart attack in the short term, unlike unstable angina caused by a large, ruptured plaque. However, MVA is far from benign and carries significant chronic risks.
The long-term outlook for individuals with MVA involves an increased risk for Major Adverse Cardiovascular Events (MACE). Studies have demonstrated that MVA is associated with an elevated risk of future heart attacks, strokes, and the development of heart failure, particularly heart failure with preserved ejection fraction. The annual incidence of MACE in some cohorts of patients with MVA has been reported to be around 7.7% per patient year.
The danger is also magnified by the presence of underlying risk factors like hypertension and diabetes, which are independent predictors of MACE in this population. While the mortality risk is generally lower than in severe obstructive CAD, it is notably higher than in the general population. The chronic nature of the disease also severely impacts quality of life, leading to frequent, debilitating chest pain that can cause anxiety, depression, and reduced capacity for work and exercise.
Effective Management and Risk Reduction
Effective management of microvascular angina focuses on two parallel goals: controlling the symptoms to improve daily life and reducing the long-term risk of cardiovascular events. Symptom management involves using medications that help improve microvascular function and control pain episodes. Traditional angina medications, such as calcium channel blockers and beta-blockers, are often used to reduce vessel spasm and heart rate, respectively.
Nitrates, which are highly effective for large-artery blockages, tend to provide less relief in MVA because they primarily target the larger blood vessels. Newer anti-anginal drugs, such as ranolazine and ivabradine, may be used when initial therapies fail to control symptoms. In cases where pain perception is heightened, low-dose tricyclic antidepressants may also be prescribed to help manage chronic chest discomfort.
Reducing long-term cardiovascular risk centers on aggressive modification of underlying risk factors. This includes lifestyle changes, such as adopting a heart-healthy diet, regular physical activity, and completely stopping tobacco use. Medications like statins and Angiotensin-Converting Enzyme (ACE) inhibitors are commonly prescribed to target the underlying endothelial dysfunction and reduce the risk of future heart attacks and stroke.