Identification of High-Risk Patients after ST-Segment-Elevation Myocardial Infarction

Background - The incidence of angiographic no reflow (NR) and microvascular obstruction (MVO) at cardiac magnetic resonance is significantly different. The aim of this study was to investigate the occurrence of NR and MVO in a cohort of consecutive patients with ST-segment-elevation myocardial infarction treated with primary percutaneous coronary interventions. Methods and Results - In this prospective study, 88 consecutive ST-segment-elevation myocardial infarction patients were enrolled within 12 hours from symptoms onset. All patients underwent cardiac magnetic resonance between 2 and 5 days after primary percutaneous coronary interventions. NR was defined as thrombolysis in myocardial infarction flow grade ≤2 and as myocardial blush grade <2. Presence of early or late MVO was assessed 4 and 10 to 15 minutes after gadolinium injection. Thirty-one patients (36%) had evidence of NR, whereas 58 (67%) had MVO. One NR patient did not have MVO. In contrast, NR was present in 30 of 58 MVO patients. MVO patients had higher troponin T peak (P<0.0001), larger late gadolinium enhancement area (P<0.0001), and lower left ventricular ejection fraction (P<0.001) because of an increased end-systolic volume (P=0.015). In contrast, patients with NR had higher troponin T peak (P=0.006) but similar late gadolinium enhancement area (P=0.24) compared with those without NR. Major cardiovascular adverse events-free survival was worse in patients with MVO (P=0.014), although it was similar in patients with and without NR (P=0.33). The independent predictors of major cardiovascular adverse events were MVO (hazard ratio, 3.418; P=0.046) and ischemic time (hazard ratio, 1.016; P<0.001). MVO was a strong predictor of target lesion revascularization occurrence (P=0.017 for log-rank test). Conclusions - Compared with coronary angiography performed soon after recanalization of the culprit artery, cardiac magnetic resonance performed during index hospitalization provides better prognostic stratification of ST-segment-elevation myocardial infarction patients treated with primary percutaneous coronary interventions. Another novel finding of our study is a significantly increased rate of clinically driven target lesion revascularization in the index event culprit vessel in patients with MVO.