Inclusion Criteria:  Age ≥18 years. Acute myocardial infarction or myocardial injury and no obstructive coronary arteries. Cardiovascular risk factor (≥1): age >70 years, atrial fibrillation, diabetes, current smoker, eGFR 30 - 60 mL/ minute/1.73 m2, prior MI, treated hypertension or COVID-19 (confirmed or suspected) Coronary angiography.  Exclusion Criteria (trial):  Obstructive coronary artery disease Left ventricular ejection fraction ≤40% with evidence of heart failure, following myocardial infarction. eGFR <30 mL/ minute/1.73 m2 Severe liver impairment Women who are pregnant, breast-feeding or of child-bearing potential (WoCBP) without a negative pregnancy test and who are unwilling or unable to follow the reproductive restrictions defined in the eligiblity criteria and use highly effective contraception as defined in Appendix 2 for the duration of the study treatment and 30 days after last dose of study drug. Patients taking one of the following medicines : Pre-existing treatment with an MRA : Anti-fungal drugs (ketoconazole or itraconazole). Antiviral medication (nelfinavir or ritonavir). Antibiotics (clarithromycin or telithromycin). Nefazodone used to treat depression. The combination of an angiotensin converting enzyme (ACE) inhibitor and an angiotensin receptor blocker (ARB)) together.  Exclusion Criteria (registry):  Contra-indication to cardiovascular magnetic resonance imaging e.g. severe claustrophobia, metallic foreign body. Contra-indication to intravenous adenosine, i.e. severe asthma; long QT syndrome; second- or third-degree atrio-ventricular block and sick sinus syndrome. Lack of informed consent.