Microvascular Angina

Patients with microvascular angina have:

• Angina that is relieved by rest or nitroglycerin

• Normal coronary angiography (eg, no atherosclerosis, embolism, or inducible arterial spasm)

Some of these patients have ischemia detected during stress testing; others do not. In some patients, the cause of ischemia seems to be reflex intramyocardial coronary constriction and reduced coronary flow reserve. Other patients have microvascular dysfunction within the myocardium: The abnormal vessels do not dilate in response to exercise or other cardiovascular stressors; sensitivity to cardiac pain may also be increased.

The diagnosis of microvascular angina requires (1, 2):

• Anginal symptoms

• Objective documentation of myocardial ischemia (ECG, perfusion, or wall motion changes during chest pain episodes or during stress testing)

• Absence of obstructive coronary artery disease by angiography, fractional flow reserve, or coronary CT angiography

• Evidence of impaired microvascular function (abnormal coronary flow reserve, microvascular resistance, resistive reserve ratio; coronary slow flow; symptoms and ECG changes in the absence of epicardial spasm during provocative testing)

This disorder should not be confused with vasospastic angina due to epicardial coronary spasm.

The mainstay of treatment is controlling risk factors with lipid-lowering therapy, glycemic control, smoking cessation, weight loss, and physical activity (3). In many patients, traditional anti-ischemic treatment, including beta-blockers and non-dihydropyridine calcium channel blockers, helps to relieve symptoms (4). Ranolazine and xanthines have also been shown to relieve symptoms in microvascular angina; some experts recommend nicorandil and short-acting amlodipine for patients already taking a beta-blocker (5).

Prognosis is better than for patients with demonstrable obstructive coronary artery disease, although symptoms of ischemia may recur for years (3). In addition, patients with microvascular angina appear to be at a higher risk for major cardiovascular events than the general population.