From the BHF Glasgow Cardiovascular Research Centre, Institute of Cardiovascular and Medical Sciences (D.C., N.A., I.M., S.R., N.S., P.W., A.R., K.G.O., C.B.) and Robertson Centre for Biostatistics (C.H., I.F.), University of Glasgow, Glasgow, United Kingdom; Golden Jubilee National Hospital, Clydebank, United Kingdom (D.C., M.M., M.C.P., H.E., S.H., S.W., M.M.L., A.D., A.M., C.B.).
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Background—The success of coronary reperfusion therapy in ST-segment–elevation myocardial infarction (MI) is commonly limited by failure to restore microvascular perfusion.Methods and Results—We performed a prospective cohort study in patients with reperfused ST-segment–elevation MI who underwent cardiac magnetic resonance 2 days (n=286) and 6 months (n=228) post MI. A serial imaging time-course study was also performed (n=30 participants; 4 cardiac magnetic resonance scans): 4 to 12 hours, 2 days, 10 days, and 7 months post reperfusion. Myocardial hemorrhage was taken to represent a hypointense infarct core with a T2* value of <20 ms. Microvascular obstruction was assessed with late gadolinium enhancement. Adverse remodeling was defined as an increase in left ventricular end-diastolic volume ≥20% at 6 months. Cardiovascular death or heart failure events post discharge were assessed during follow-up. Two hundred forty-five patients had evaluable T2* data (mean±age, 58  years; 76% men). Myocardial hemorrhage 2 days post MI was associated with clinical characteristics indicative of MI severity and inflammation. Myocardial hemorrhage was a multivariable associate of adverse remodeling (odds ratio [95% confidence interval]: 2.64 [1.07–6.49]; P=0.035). Ten (4%) patients had a cardiovascular cause of death or experienced a heart failure event post discharge, and myocardial hemorrhage, but not microvascular obstruction, was associated with this composite adverse outcome (hazard ratio, 5.89; 95% confidence interval, 1.25–27.74; P=0.025), including after adjustment for baseline left ventricular end-diastolic volume. In the serial imaging time-course study, myocardial hemorrhage occurred in 7 (23%), 13 (43%), 11 (33%), and 4 (13%) patients 4 to 12 hours, 2 days, 10 days, and 7 months post reperfusion. The amount of hemorrhage (median [interquartile range], 7.0 [4.9–7.5]; % left ventricular mass) peaked on day 2 (P<0.001), whereas microvascular obstruction decreased with time post reperfusion.Conclusions—Myocardial hemorrhage and microvascular obstruction follow distinct time courses post ST-segment–elevation MI. Myocardial hemorrhage was more closely associated with adverse outcomes than microvascular obstruction.Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique identifier: NCT02072850.