Heterogeneity of coronary vascular function and myocardial oxygenation in women with angina and non-obstructive coronary artery disease

Women with angina and non-obstructive coronary artery disease (ANOCA) have a heightened risk for cardiovascular events, and the pathophysiology for ischaemic symptoms may be related to alterations in microvascular structure and function. We examined the use of breathing-enhanced oxygenation-sensitive cardiac magnetic resonance imaging (OS-CMR) using vasoactive breathing manoeuvres to assess myocardial oxygenation in women with ANOCA. We recruited women (aged 40-65 years) from two sites in Canada who presented to healthcare with persistent retrosternal chest pain and found to have ANOCA, or without a history of cardiovascular disease. All participants were scanned using a clinical 3T MRI scanner, and OS-CMR images were acquired over a breath hold following paced hyperventilation to measure global and regional measurements of heterogeneity. Fifty-four women with ANOCA (age: 55 ± 6.2 years) and 48 healthy controls (age: 51.2 ± 4.8 years) were recruited. There was no significant difference in volume, function, mass, or global myocardial oxygenation between the two groups [mean %Δ in signal intensity (SI): 4.9 (±7.3) vs. 4.5 (±10.1), P = 0.82]. Women with ANOCA had higher regional variations in myocardial oxygenation in circumferential [median %Δ in SI: 5.1 (2.0-7.6) vs. 2.2 (1.4-3.5), P = 0.0004] and longitudinal directions [median %Δ in SI: 11.4 (5.4-16.7) vs. 6.0 (3.0-7.0), P = 0.001], which remained present in a multivariate model. Heterogeneous myocardial oxygenation may explain ischaemic symptoms without any associated epicardial obstructive coronary artery disease. Regional variations in myocardial oxygenation on OS-CMR could serve as an important diagnostic marker for microvascular dysfunction in women with ANOCA.