Introduction: Myocardial infarction (MI) is typically attributable to obstructive atherosclerotic coronary artery disease (CAD) producing ischemic necrosis, however in 10% of MI patients this may occur in the absence of obstructive CAD. This study prospectively compares patients with MI and CAD (MICAD) to those with MI and non-obstructive coronary arteries (MINOCA) in relation to (a) initial chest pain presentation, (b) risk factors, and (c) discharge therapies.
Methods: Consecutive patients undergoing coronary angiography for acute MI were captured in the Coronary Angiogram Database of South Australia (CADOSA) registry. Patients were categorised as MICAD or MINOCA on the basis of the universal criteria for MI and either the presence (≥50%) or absence (<50%) of an obstructive stenosis (≥50%) on angiography, respectively. Patients with a non-coronary cause for their clinical presentation (eg myocarditis or cardiomyopathy) were excluded.
Results: Between January 2012 and December 2013, from 3,277 angiographic procedures undertaken for acute MI, 89% (2923) were classified as MICAD, 7% (219) as MINOCA, and 4% (135) as non-coronary causes. Compared with MICAD, patients with MINOCA are younger (64 (54,74) vs 60 (48,71) years, p<0.01) and more likely to be female (26% vs 57%, p<0.01). The initial chest pain presentation was similar between MICAD and MINOCA in relation to site, quality, and associated symptoms. MINOCA patients have fewer risk factors compared to MI-CAD (p<0.05): current smoking (25% vs 34%), dyslipidaemia (49% vs 61%) and diabetes (22% vs. 32%), except for hypertension (61% vs 66%, p>0.05). At discharge, MINOCA patients are less likely to receive preventative therapies compared to MICAD (p<0.01); antiplatelet agents (76% vs 95%); statin (69% vs 88%); angiotensin converting enzyme inhibitors/angiotensin receptor blockers (62% vs 82%) and beta blockers (41% vs 66%).
Conclusions: Although MINOCA patients are more often female and younger, their presenting chest pain features are indistinguishable from those with MICAD. Despite an ischemic presentation, MINOCA patients are less likely to receive cardio-protective agents at discharge. Future studies identifying appropriate medical management for MINOCA are warranted.