Prevalence of microvascular angina among patients with stable symptoms in the absence of obstructive coronary artery disease: a systematic review.

Our purpose was to perform a systematic review to assess the prevalence of microvascular angina (MVA) among patients with stable symptoms in the absence of obstructive coronary artery disease (CAD). We performed a systematic review of the literature to group the prevalence of MVA, based on diagnostic pathways and modalities. We defined MVA using three definitions: (i) suspected MVA using non-invasive ischaemia tests; proportion of patients with non-obstructive CAD among patients with symptoms and a positive non-invasive ischaemia test result, (ii) suspected MVA using specific modalities for MVA; proportion of patients with evidence of impaired microvascular function among patients with symptoms and non-obstructive CAD, and (iii) definitive MVA; proportion of patients with positive ischaemia test results among patients with an objectified impaired microvascular dysfunction. We further examined the ratio of women-to-men for the different groups. Of the 4547 abstracts, 20 studies reported data on MVA prevalence. The median prevalence was 43% for suspected MVA using non-invasive ischaemia test, 28% for suspected MVA using specific modalities for MVA, and 30% for definitive MVA. Overall, more women were included in the studies reporting sex-specific data. The women-to-men ratio for included participants was 1.29. However, the average women-to-men ratio for the MVA cases was 2.50. In patients with stable symptoms of ischaemia in the absence of CAD, the prevalences of suspected and definitive MVA are substantial. The results of this study should warrant cardiologists to support, promote and facilitate the comprehensive evaluation of the coronary microcirculation for all patients with symptoms and non-obstructive CAD.