Clinical meaning
Microvascular angina (cardiac syndrome X) results from dysfunction of the coronary microcirculation rather than epicardial coronary artery stenosis. The pathophysiology involves endothelial dysfunction of the coronary arterioles (impaired nitric oxide-mediated vasodilation and enhanced endothelin-1-mediated vasoconstriction), abnormal smooth muscle hyperreactivity, and inflammation with increased myocardial wall stress, causing reduced coronary flow reserve and myocardial ischemia despite angiographically normal coronary arteries. Patients (predominantly women) present with typical anginal chest pain provoked by exertion or emotional stress, with positive stress test findings (ST depression) but normal coronary angiography. Diagnosis is confirmed by invasive coronary reactivity testing demonstrating abnormal coronary flow reserve (less than 2.5), abnormal index of microvascular resistance, or coronary spasm with acetylcholine provocation. The nurse assesses chest pain using standardized pain assessment tools, monitors vital signs during anginal episodes, administers prescribed medications (beta-blockers, calcium channel blockers, ranolazine, ACE inhibitors), educates patients about the cardiac origin of their symptoms (validating that the pain is real despite normal angiogram), promotes cardiac risk factor modification, and monitors for treatment response.