Abstract 273: Myocardial Infarction with Non Obstructive Coronary Artery Disease: Prevalence, Clinical Features and Outcomes

Abstract

Background: Myocardial infarction with non-obstructive coronary arteries (MINOCA) is an enigma that is being increasingly recognized with the frequent use of angiography following Acute Myocardial Infarction (AMI). The current study is a prospective, contemporary analysis of MINOCA vs. Myocardial Infarction with obstructive coronary artery disease (MI-CAD) in regards to prevalence, clinical features, and in-hospital outcomes. Methods: All consecutive patients undergoing coronary angiography for AMI (as per the Third Universal AMI Definition) in South Australian public hospitals from January 2012 - December 2013 were included. Data was captured by Coronary Angiogram Database of South Australia (CADOSA), a comprehensive registry compatible with the NCDR® CathPCI® Registry. The AMI patients were classified as MI-CAD or MINOCA on the basis of the presence or absence of a significant stenosis (≥50%) on angiography. Results: From 4,189 angiography procedures undertaken for AMI, 468 (11%) were classified as MINOCA. Patients with MINOCA were younger (59±15 vs. 64±13 years, p <0.01) and more likely to be female (53% vs. 26%, p <0.01), compared to those with MI-CAD. Age-adjusted analysis comparing patients with MINOCA to MI-CAD revealed differences in: (1) cardiovascular risk factors including hypertension (52% vs. 66%, p<0.01), diabetes (19% vs. 32%, p<0.01), dyslipidemia (46% vs. 62%, p<0.01), and current smoker status (27% vs. 37% p<0.01); (2) AMI type and size with fewer ST elevation myocardial infarcts (27% vs. 41%, p<0.01) and lower peak troponin values (180 ng/L, IQR 353 vs. 264 ng/L, IQR 680, p<0.01) amongst MINOCA patients. Furthermore, the GRACE Score for acute coronary syndrome risk stratification was lower for the MINOCA patients compared to MICAD (150±34 versus 160±35, p <0.01). Despite fewer cardiovascular risk factors, the absence of obstructive coronary artery disease, smaller infarcts, and a lower GRACE score, the in-hospital mortality was similar for MINOCA and MI-CAD patients (2.2% vs. 3.0%, p=0.22). Moreover, MINOCA patients were less likely to receive secondary prevention therapies at discharge including antiplatelet therapy (60% vs. 92%, p<0.01) beta-blockers (41% vs. 65%, p<0.01), statin (55% vs. 88%, p<0.01), ACE-inhibitor/angiotensin receptor blocker (59% versus 81%, p<0.01), or referral to cardiac rehabilitation (15% versus 52%, p<0.01). Conclusions: In contemporary cardiology practice, MINOCA may be more frequent than previously appreciated and has a guarded prognosis despite its apparent lower risk profile. Improving the use of secondary prevention therapies in these patients may improve their prognosis.