RESUMO
BACKGROUND: Despite improvement in revascularization strategies, microvascular obstruction (MO) lesions remain associated with poor outcome after ST-segment elevation myocardial infarction (STEMI). AIMS: To establish a bedside-available score for predicting MO lesions in STEMI, with cardiac magnetic resonance imaging (CMR) as the reference standard, and to test its prognostic value for clinical outcome. METHODS: Patients with STEMI of<12 hours' evolution treated by percutaneous coronary intervention (PCI) were included. CMR was performed 4-8 days later, to measure myocardial infarction (MI) extent, left ventricular ejection fraction (LVEF) and volumes, and to identify MO lesions. An MO score was built from multivariable logistic regression results and included clinical, angiographic and electrocardiographic criteria. Adverse cardiovascular events were recorded prospectively after STEMI. RESULTS: We analysed data from 112 patients. MO lesions were found in 63 (56%) patients and were associated with larger MI as assessed by higher peak creatine phosphokinase (3755 ± 351 vs 1467 ± 220 IU, p<0.001), lower LVEF (46.7 ± 1.5 vs 53.4 ± 1.6%, p<0.01) and larger MI extent (18.7 ± 1.2 vs 9.0 ± 1.3% LV, p<0.001) on CMR. MO score>4 accurately identified microcirculatory injuries (sensitivity 84%; specificity 82%) and independently predicted the presence of MO lesions on CMR. MO score>4 predicted adverse cardiovascular events during the first year after STEMI (relative risk 2.60 [1.10-6.60], p=0.03). CONCLUSIONS: MO lesions are frequent in PCI-treated STEMI and are associated with larger MIs. MO score accurately predicted MO lesions and identified patients with poor outcome post-STEMI.
