Rate of acute myocardial infarction in patients with troponin-positive chest pain and unobstructed coronary arteries

Abstract

Background Many patients with troponin-positive chest pain are initially diagnosed with acute myocardial infarction (AMI), but are later found to have nonobstructive coronary artery disease (CAD) by x-ray angiography. CMR may be useful in this diagnostically challenging cohort; the presence and/or pattern of myocardial necrosis identified by CMR may allow differentiation between diverse etiologies such as AMI, myocarditis, Takotsubo cardiomyopathy, among others. AMI may occur despite nonobstructive CAD, since plaque rupture with occlusive thrombosis may be followed by recanalization. Nevertheless, the diagnosis of AMI is critical for patient management. Prior CMR studies of this population report aw ide range in the rate of AMI (5%30%), perhaps because existing studies have limited sample size (20-130 patients). The aim of this study was to determine the rate of AMI in a larger patient population with troponin-positive chest pain and unobstructed coronary arteries and to examine clinical characteristics that may be associated with this diagnosis. Methods This single-center prospective study enrolled consecutive patients who presented with troponin-positive chest pain, had obstructive CAD (>50% stenosis) excluded by invasive coronary angiography, and then were referred for CMR. A comprehensive set of clinical characteristics including CAD risk factors and peak troponin levels were collected. Angiographic atherosclerosis severity was categorized as entirely normal (0%), near-normal (1-25% stenosis), and mild atherosclerosis (>25-50% stenosis). Hyperenhancement in a CAD-pattern on delayed-enhancement CMR was used to determine the diagnosis of AMI.