Novel diagnostic criterion for microvascular ischaemia using cmr perfusion imaging: validation against invasive index of microvascular resistance

In over 50% of patients with angina, the underlying ischaemia is related to microvascular dysfunction (MVD), rather than epicardial coronary artery disease (CAD). Clinically, MVD remains a major diagnostic challenge, which hinders targeted therapy and confers impaired clinical outcomes. Myocardial perfusion reserve (MPR), as assessed by cardiovascular magnetic resonance (CMR), is impaired in those with microvascular angina. We sought to objectively diagnose microvascular ischaemia using CMR by defining an MPR cutoff, validated against invasive coronary microvascular physiology (Index of Microvascular Resistance, IMR)