MICRO MI – Investigating Coronary Microvascular Dysfunction in MINOCA

Coronary Microvascular Dysfunction (CMD) in Myocardial Infarction with Non-Obstructive Coronary Arteries

Myocardial infarction with non-obstructive coronary arteries (MINOCA) accounts for around 10% of all heart attacks and presents a major diagnostic challenge, as standard coronary angiography cannot identify an underlying cause. Coronary microvascular dysfunction (CMD) — impaired function of the small vessels making up over 90% of the heart's blood supply — is increasingly suspected as a key contributor, yet it remains poorly understood and unstudied in this population, despite roughly one in four MINOCA patients continuing to experience angina a year after their initial event.

The MICRO MI study will use a novel, non-invasive cardiac MRI technique — oxygenation-sensitive CMR combined with the Breathing-Induced Myocardial Oxygenation Reserve (B-MORE) protocol — to detect CMD without contrast or radiation, by measuring how the heart's microvasculature responds to controlled breathing manoeuvres. The primary aims of the MICRO MI study are to evaluate the feasibility and diagnostic performance of B-MORE CMR for detecting CMD in MINOCA, and to characterise its prevalence and physiological features, comparing MINOCA patients against those with obstructive coronary disease, hypertensive controls, and healthy controls.