Frishman, William

Coronary microvascular dysfunction (CMD) is increasingly recognized as a central mechanism underlying myocardial ischemia, heart failure with preserved ejection fraction, and adverse cardiovascular outcomes in patients with and without obstructive coronary artery disease. The coronary microcirculation plays a critical role in regulating myocardial perfusion through tightly coordinated myogenic, metabolic, and endothelial pathways. Disruption of these mechanisms results in impaired vasodilatory capacity, abnormal coronary flow reserve, and microvascular ischemia. This review summarizes the anatomy and physiology of coronary microcirculation and examines the pathophysiologic mechanisms driving CMD, including endothelial dysfunction, structural remodeling, inflammation, and neurohormonal dysregulation. Contemporary diagnostic strategies are reviewed, with emphasis on invasive coronary function testing and advanced noninvasive imaging modalities such as positron emission tomography and cardiac magnetic resonance imaging. The clinical implications of CMD across diverse disease states, including ischemia with nonobstructive coronary arteries, heart failure, and cardiomyopathies, are discussed. Finally, current therapeutic approaches, prognostic considerations, and emerging research directions aimed at improving diagnosis and targeted treatment of CMD are highlighted.

Coronary artery spasm (CAS) is a dynamic vasomotor disorder characterized by transient, intense constriction of epicardial coronary arteries, leading to myocardial ischemia in patients with and without obstructive coronary artery disease. CAS plays a central role in vasospastic angina, ischemia with nonobstructive coronary arteries and myocardial infarction with nonobstructive coronary arteries, malignant arrhythmias, and sudden cardiac death. Its pathophysiology is multifactorial, involving endothelial dysfunction, vascular smooth muscle hyperreactivity, inflammation, oxidative stress, autonomic imbalance, and genetic susceptibility, with notable ethnic and sex-related differences. Diagnosis relies on integration of clinical features, electrocardiographic changes, and invasive coronary provocation testing using acetylcholine or ergonovine, supported by advanced imaging and functional assessment when microvascular involvement is suspected. Management is centered on calcium channel blockers and nitrates, aggressive risk factor modification, particularly smoking cessation, and individualized strategies for refractory or high-risk patients. Improved recognition and standardized diagnostic pathways are essential to optimize outcomes and reduce life-threatening complications associated with CAS.