Microvascular dysfunction: what have we learned from WISE?

Abstract

“Emerging data show that subsets of patients, most of whom are women, present without important epicardial obstruction but with ischemia markers.” Ischemic heart disease remains a leading contributor of morbidity and mortality among women. Although the link between epicardial coronary artery disease (CAD) and adverse outcomes established over past decades is well known, a subset of patients with signs and symptoms of ischemia have no obstructive epicardial CAD. Emerging data show that subsets of patients, most of whom are women, present without important epicardial obstruction but with ischemia markers, suggesting that other pathophysiological mechanisms contribute to ischemia-related adverse outcomes. Accumulating evidence supports microvascular dysfunction (MVD) as an important component of the explanation for ischemia and its relation to adverse outcomes. Among women with signs and symptoms of ischemia and angiographically ‘normal’ coronary vessels, MVD was first suggested in 1967 [1], and in 1983 inappropriate coronary flow increases to vaso motor stimuli were described [2]. The term ‘microvascular angina’ was proposed for patients with documented MVD by a limited coronary flow response to stimuli, such as rapid atrial pacing, adenosine and/or acetylcholine. Although evidence for MVD has been presented for both women and men, women appear disproportionately represented for reasons that are incompletely understood. Perhaps estrogen or other genetic and environmental milieu contribute to the stunted development of epicardial obstructive lesions, but not the underlying microvascular pathology. Alternatively, perhaps such milieu amplify microvascular abnormalities in women.