Comparison of clinical characteristics, treatments and outcomes of patients with ST-elevation acute myocardial infarction with versus without new or presumed new left bundle branch block (from NCDR®).

Guidelines recommend urgent reperfusion for patients with new left bundle branch block (LBBB), similar to patients with ST-segment elevation myocardial infarction (STEMI). However, there are limited contemporary data comparing these 2 groups of patients. Patients presenting with acute STEMI or presumed new LBBB (nLBBB) enrolled in the Acute Coronary Treatment and Intervention Outcomes Network (ACTION) Registry-Get With the Guidelines (GWTG) from January 2007 to March 2009 were evaluated for clinical characteristics, treatment patterns, and outcomes. Logistic generalized estimating equation modeling was used to examine associated risk-adjusted mortality. Of 46,006 patients with either STEMI or nLBBB, 44,405 (96.5%) had STEMI, and 1,601 (3.5%) had nLBBB. Overall, patients with nLBBB had more baseline co-morbidities compared to those with STEMI. Compared to patients with STEMI, those with nLBBB were less likely to receive acute reperfusion (93.9% vs 48.3% p <0.0001) and were less likely to have door-to-balloon times ≤90 minutes (76.8% vs 34.5%, p <0.0001). Mortality rates were higher for patients with nLBBB compared to those with STEMI (13.3% vs 5.6%, p <0.0001). After multivariate adjustment, nLBBB was not associated with an increased risk for in-hospital mortality (odds ratio 0.91, 95% confidence interval 0.75 to 1.12, p = 0.38). In conclusion, patients with nLBBB were clinically different from those with STEMI, with significantly more co-morbidities, and were less likely to receive emergent reperfusion therapy. Despite these differences, adjusted mortality rates were similar between patients with nLBBB and those with STEMI.