Microvascular angina is a condition similar to a heart disease, called angina pectoris. Patients with microvascular angina also complain of chest pain, but the doctor’s initial diagnosis is often coronary artery disease (CAD). Imaging studies, such as coronary angiography, would show that the heart is normal. While angina pectoris and other CADs are caused by inadequate blood flow through the coronary arteries, microvascular angina is due to insufficient flow through the microvasculature, or tiny blood vessels, of the heart. It is curable with the right combination of healthy diet, regular exercise, and blood vessel-dilating medications.
Among patients who complain of chest pain and are subsequently evaluated through coronary angiography, approximately 20 to 30% have normal angiograms. In 1988, Cannon and Epstein coined the term microvascular angina for this combination of exertional chest pain and a completely normal angiogram, with or without electrocardiogram (ECG) changes on exercise testing. It is also known as cardiac syndrome X, because its actual causes remain unknown.
Several pathophysiological mechanisms for severe chest pain have been proposed. The most important of these is myocardial ischemia, wherein the function or anatomy of the coronary microvasculature is abnormal. There could be a decrease in the capacity of the blood vessels to dilate or increase their diameter, leading to a blood supply compromise, as well as nutrient and oxygen deprivation of the heart muscle. Another proposed mechanism is that the heart muscle suffers from metabolic derangement, leading to decreased glucose intake and utilization by the myocardium. One more proposed mechanism is that there is increased sensitivity of pain receptors to stimuli arising from the heart.
Although the real causes of microvascular angina remain unidentified, several risk factors are known. These include abdominal obesity or excessive fat deposition in the abdomen, dyslipidemia or abnormal blood lipids, hypertension, glucose intolerance or insulin resistance, and pro-inflammatory states like diabetes mellitus. Cardiac syndrome X is often associated with insulin resistance and central obesity, so it is sometimes called insulin resistance syndrome. People in the high risk category include women, the elderly, and those who have a family member who has a history of heart disease.
When a person goes to the doctor complaining of severe chest pain, microvascular angina is not normally the initial diagnosis. A battery of tests is needed before the doctor can say that the patient’s condition is not esophageal spasm, angina pectoris, Prinzmetal’s angina, or heart attack. The usual tests performed include treadmill or stress electrocardiographic testing, coronary angiogram, and sometimes magnetic resonance imaging (MRI) of the heart.
Once microvascular angina has been diagnosed, the doctor prescribes medications, such as dilatiazem and nifedipine, that are intended to relieve chest pain and improve the patient's quality of life. Other alternatives include beta-blockers like carvedilol and propranolol, L-arginine, estrogen, and aminophylline. Many of the risk factors for microvascular angina are avoidable, so it is important to address them by eating a healthy diet, engaging in daily physical activities, and visiting the doctor regularly.