Diagnose underlying aetiology with Intravascular Assessment versus Cardiac Magnetic Resonance Imaging in patients with Myocardial Infarction with Non-Obstructive Coronary Arteries (DETECT-MINOCA)

DETECT-MINOCA Algorithmic Pathway (Intervention Arm) - Participants randomised to the DETECT-MINOCA algorithm undergo further investigation stratified by their Left Ventricular Ejection Fraction (LVEF) and regional wall motion patterns: A) Patients with preserved LVEF or regional wall motion abnormalities: - Optical Coherence Tomography (OCT): Performed immediately following coronary angiography in the catheterisation lab. OCT uses a near-infrared light source delivered via an intracoronary catheter to image vessel morphology with high resolution. A small amount of contrast (~15mL) is used during image acquisition per vessel. The procedure takes approximately 10–15 minutes.for one vessel and 15-20 minutes for all 3 epicardial vessels. - Acetylcholine (ACh) Provocation Testing (optional): If OCT does not yield a definitive diagnosis, intracoronary ACh is administered to test for vasospasm. A 20–100 µg dose is injected directly into the coronary artery, with angiographic monitoring for vasoconstriction and symptoms. This adds approximately 5 minutes to the procedure. In some cases (e.g., RCA testing), a temporary pacing wire may be inserted as a safety precaution. - Cardiac Magnetic Resonance Imaging (CMR): If both OCT and ACh-provocation yields no diagnosis, CMR is performed as an inpatient prior to discharge. It involves a 30–40 minute scanning session with cine imaging, late gadolinium enhancement (LGE), and T1/T2 mapping. Gadolinium contrast (0.2 mmol/kg) is administered intravenously. CMR identifies both ischaemic and non-ischaemic myocardial injury. B) Patients with reduced LVEF and regional wall motion abnormality: These patients also proceed with OCT ± ACh testing, prioritising the vessel corresponding to the affected myocardial territory. If no pathology is found in the suspected culprit artery, OCT ± ACh may be extended to the remaining vessels. CMR is conducted if invasive testing yields no diagnosis. C) Patients with globally or severely reduced LVEF: These patients bypass invasive assessment and proceed directly to CMR. Timing: All invasive assessments (OCT ± ACh) are conducted within the index coronary angiogram procedure (i.e., immediately after angiographic diagnosis of MINOCA). CMR, if indicated, is performed within the index hospital admission, typically within 2–3 days of admission.