The clinical impact of cardiac magnetic resonance imaging upon suspected myocardial infarction with non-obstructive coronary artery disease

Abstract Background Cardiac magnetic resonance (CMR) may identify the underlying pathology in myocardial infarction with non-obstructed coronary arteries (MINOCA), however there are scant prospective data evaluating the more important measure of actual change in diagnosis and management consequent to CMR. Purpose To evaluate impact of CMR in MINOCA upon diagnosis, diagnostic certainty and management, adjudicated by treating physicians to minimise investigator bias. Methods Prospective, multi-center international pre- and post-CMR study of suspected MINOCA. Physician diagnosis, diagnostic certainty and intended management were established by questionnaire before and after CMR. The primary outcome was change in diagnosis or management. Secondary outcomes were change in diagnosis, change in management, change in diagnostic certainty, and number-needed-to-test for de-prescription of dual antiplatelet therapy (DAPT). Potential predictors of impactful CMR were evaluated by multivariable logistic regression analysis. Results 320 patients referred by 74 clinicians underwent CMR; mean age 55.6 (12.3) years, 48.1% female. CMR was conducted at median 11 days (IQR 6-19) post presentation. CMR led to change in diagnosis or management in 62.8% (95% CI 57.4% - 68.2%, p<0.0001) and significantly increased diagnostic certainty [8/10 post-CMR (5-9) vs 6/10 pre-CMR (4-7), p<0.0001]. Predictors of impactful CMR on multivariable analysis were early CMR (≤14 days), absence of atheroma on coronary angiography, significant pre-CMR diagnostic uncertainty (≤5/10), and a history of vascular disease. DAPT was deprescribed or modified to single antiplatelet in 61.7% patients. The number-needed-to-test to deprescribe DAPT was 2.6 (and 1.6 if a myocardial infarction mimic was co-suspected pre-CMR), which has important cost-benefit implications for CMR in MINOCA. Conclusions In this first prospective multi-centre study of CMR in MINOCA where diagnostic utility was adjudicated by the treating physicians, CMR was associated with frequent and significant changes in diagnosis, clinician certainty and clinical care, including frequent de-prescription of DAPT. Early CMR is to be encouraged, particularly in patients where there is significant diagnostic uncertainty and no atheroma on coronary angiography.