Background and Purpose - We aimed to use contrast-enhanced cardiac magnetic resonance (CE-CMR) imaging to elucidate the prevalence of left ventricular (LV) thrombus in patients suspected of embolic stroke of undetermined source (ESUS) with previous myocardial infarction or LV dysfunction (LV ejection fraction [LVEF] <50%). Methods - We prospectively investigated 797 consecutive patients who presented to our hospital with acute ischemic stroke between 2014 and 2015. Patients with myocardial infarction or LVEF<50% underwent CE-CMR imaging. ESUS was diagnosed according to proposal criteria based on transthoracic echocardiography findings. Results - The prevalence of ESUS was 22% (178 of 797) on initial diagnosis. Among 60 patients with myocardial infarction or LVEF<50%, the stroke subtypes were as follows: small artery disease, 17% (10 of 60); large artery atherosclerosis, 5% (3 of 60); cardioembolic stroke, 49% (29 of 60); ESUS, 23% (14 of 60); and undetermined causes other than ESUS, 6% (4 of 60). Of 60 patients examined via CE-CMR, LV thrombus was confirmed in 12 patients, whereas only 1 had been detected on transthoracic echocardiography (P=0.04). Importantly, 29% (4 of 14) of patients with ESUS had LV thrombus. A prediction model based on CE-CMR findings showed higher performance in LV thrombus detection, permitting a net improvement of 0.46 (95% confidence interval, 0.08-0.82; P=0.016) in cardioembolic stroke reclassification. Compared with patients without LV thrombus, those with LV thrombus had lower LVEF (median: 26% versus 40%; P=0.003). Notably, 42% (5 of 12) of patients with LV thrombus had LVEF≥30%. Conclusions - When ESUS-suspected patients have myocardial infarction or LV dysfunction, CE-CMR may help improve detection of cardioembolic stroke and provide relevant information for anticoagulation therapy.
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