The systematic performance of cardiac magnetic resonance imaging (CMR) could play a pivotal role in providing the underlying cause of myocardial infarction with non-occlusive coronary arteries (MINOCA).

This study aimed to describe the characteristics of the patients hospitalised for MINOCA and to assess the proportion of patients for whom CMR provided the underlying diagnosis of MINOCA.

Between May 2015 and August 2018, 457 patients with MINOCA were prospectively enrolled in an observational cohort study in 15 centres affiliated to the Collège national des cardiologues des hôpitaux (CNCH). Prior to CMR, the cardiologist established one of the following diagnoses: “type 1 MI”, “type 2 MI”, “myocarditis”, “TTS”, “other diagnoses”, and “uncertain diagnosis” (when no diagnosis was established). Using CMR findings, the cardiologist reassigned the patient to one of the 6 subgroups.

In total, 336 of 457 patients with MINOCA underwent CMR. CMR was able to identify a diagnosis in 90.5% of cases, and changed the underlying cause in 35.7% of patients; 33.7% of type 1 MI were not diagnosed prior to CMR. Patients with a normal CMR had a significantly longer median time to complete the CMR (17 vs. 7 days, P=4.2E⁻⁷) and lower conventional and high sensitivity troponin values (respectively 1.1 vs. 3.6μG/L, P=0.002 and 433.3 vs. 707.1ng/L, P=0.007). At 1-year follow-up of the CMR cohort, the prevalence of all-cause mortality was 3%, of cardiac mortality 0.6% and of rehospitalisation for cardiac causes 7.8%. No bleeding disorders occurred after increased anti-platelet therapy in patients re-diagnosed with MI (Fig. 1).

CMR provided a diagnosis in 9 out of 10 patients presenting with MINOCA. The diagnosis differed from the one prior to CMR in 35.7% of patients. The systematic use of CMR plays a pivotal role in identifying the underlying cause of myocardial injury, impacting both individuals, health professionals and society at large.