318 Diagnostic Utility of Cardiac Magnetic Resonance (CMRI) in Patients with Myocardial Infarction without Obstructive Coronary Arteries (MINOCA)

Abstract

Background: The underlying aetiology in patients presenting with myocardial infarction and non-obstructive coronary arteries (MINOCA) is varied and has important implications for treatment and prognosis. Cardiac MRI (CMRI) may help clarify the underlying cause in MINOCA. We aimed to evaluate the diagnostic utility of CMRI in this setting. Methods: 995 consecutive patients referred to a tertiary referral hospital for CMRI (January 2016-December 2019) were screened. Patients meeting the Fourth Universal Definition of Myocardial Infarction without obstructive coronary artery disease (50% stenosis) were included. The underlying cause of MINOCA was determined using standard CMRI criteria and peak high-sensitivity troponin T (HsTropT) compared among patients with and without a CMRI diagnosis. Results: 46 MINOCA cases were identified (52.2615.5 years, 59% male). CMRI was normal in 16/46 (35%) patients. Among the 30/46 (65%) patients with an abnormal CMRI, diagnoses included myopericarditis (14/46, 30%), myocardial infarction (8/46, 17%), Takotsubo (5/46, 11%) and hypertrophic (3/46, 7%) cardiomyopathy. Median HsTropT was 343 (117-713) ng/L overall but significantly lower in patients with a normal CMR (129 (26-343) vs 590 (203-1367) ng/L, p=0.0002). HsTropT had high diagnostic accuracy for predicting a CMRI abnormality by ROC analysis (AUC 0.83, p=0.004). A HsTropT value .262ng/L was 71% sensitive and 73% specific for predicting an abnormal CMRI and all patients with a HsTropT .637ng/L had an abnormal CMRI. Conclusion: Patients with MINOCA are a heterogenous cohort and CMRI identifies a cause in almost two-thirds of cases. Peak HsTropT may help guide selection of MINOCA patients for CMRI referral.