Coronary Vasomotion Syndromes

Epicardial spasm reflects transient narrowing in a major coronary artery, whereas microvascular dysfunction reflects inadequate dilation in the smaller coronary vessels. Either mechanism can restrict myocardial blood flow and produce ischemia, and both may occur in the same patient. Distinguishing these patterns helps clinicians connect symptoms and ischemic findings with the underlying vascular abnormality.

An unobstructed appearance on coronary imaging does not exclude a temporary or functional reduction in blood flow. Transient epicardial narrowing may resolve, while impaired microvascular dilation may not be visible in the major arteries. Consequently, patients can experience angina and ischemic electrocardiographic changes even when imaging does not show a fixed obstructive lesion.

Endothelial dysfunction can interfere with normal regulation of coronary vascular tone, reducing the ability of vessels to adjust blood flow appropriately. Heightened vascular smooth-muscle reactivity can further favor excessive constriction, particularly in the epicardial arteries. Together, these abnormalities provide a mechanistic explanation for episodic ischemia occurring at rest, with exertion, or during stress.

Evaluation combines clinical assessment with coronary imaging and, when appropriate, provocative testing. The clinical assessment characterizes symptoms and their relationship to rest, exertion, or stress, while imaging examines the major coronary arteries. Provocative testing can challenge coronary vascular regulation and may help identify vasomotor abnormalities that routine anatomical imaging does not demonstrate.

When considered appropriate, acetylcholine provocative testing is used to examine how the coronary circulation responds to a vasoactive challenge. The response can support recognition of abnormal vasomotion, including a tendency toward epicardial spasm or impaired regulation involving the microcirculation. This functional information complements coronary imaging and can clarify the mechanism behind ischemic symptoms.

Recognizing whether ischemia reflects abnormal coronary tone helps clinicians select targeted management rather than relying only on the appearance of major arteries. Vasodilator therapy is included among treatment approaches because it addresses excessive or inadequate vascular regulation. Mechanistic recognition also explains why patients with unobstructed arteries may still have ischemic electrocardiographic changes and adverse cardiovascular outcomes.