Incidence, Predictors, and Outcomes of High-Grade Atrioventricular Block in Patients With ST-Segment Elevation Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention (from the HORIZONS-AMI Trial)

High-grade atrioventricular block (HAVB) is historically considered a marker of worse outcomes in patients with ST-segment elevation myocardial infarction (STEMI). However, the predictors and prognostic impact of HAVB in the primary percutaneous coronary intervention (PCI) era remain poorly understood. We sought to describe the characteristics and predictors of HAVB in patients undergoing primary PCI in STEMI and to assess the prognostic significance of HAVB in the contemporary reperfusion era. The present analysis includes 3,115 patients presenting with STEMI from the Harmonizing Outcomes with Revascularization and Stents in Acute Myocardial Infarction trial who underwent primary PCI. Outcomes were examined according to the presence of HAVB on a presenting electrocardiogram, as interpreted by an independent electrocardiography core laboratory. HAVB (second-degree Mobitz II or third-degree atrioventricular block) was present at baseline in 46 patients (1.5%). Independent predictors of HAVB included increased age, diabetes mellitus, right coronary artery occlusion, sum of ST-segment deviation, and baseline Thrombolysis In Myocardial Infarction flow 0/1. Thrombolysis In Myocardial Infarction flow 3 was restored in 83.7% and 91.5% of patients with versus without baseline HAVB respectively (p = 0.06). Mortality rate was significantly higher in patients with versus without HAVB at 30-day, 1-, and 3-year follow-ups (unadjusted hazard ratio [HR] 3.83, 95% CI 1.40 to 10.48; unadjusted HR 4.37, 95% CI 2.09 to 9.38 and unadjusted HR 2.78, 95% CI 1.31 to 5.91, respectively). After covariate adjustment, mortality rate was significantly higher in patients with HAVB at 1 year (adjusted HR 2.45, 95% CI 1.09 to 5.50, p = 0.03) but not at 30 days (adjusted HR 1.70, 95% CI 0.58 to 5.01, p = 0.33) or 3 years (adjusted HR 0.71 to 3.41, p = 0.27). In conclusion, HAVB is a rare complication of STEMI but remains associated with increased mortality, even after primary PCI.