Whether patients with acute myocardial infarction presenting with new or presumed new left bundle-branch block (LBBB) should be treated in the same way as those presenting with ST-elevation (STE) is still a matter of debate.

Data from 28,358 patients enrolled in AMIS Plus from 1997 to 2016 were analyzed to evaluate differences in treatment and outcome of patients presenting with LBBB (n=2295) or STE (n=26,090) on their initial electrocardiogram using descriptive statistics and multivariate logistic regression.

LBBB patients were older (75.0 vs 64.3 years, P<.001) with a greater burden of risk factors and comorbidities. They were admitted 80 minutes later and more frequently in Killip III/IV (20% vs 7%, P<.001). Even after adjustment for age and gender, LBBB patients were less likely to receive aspirin (odds ratio [OR] 0.40, 95% CI 0.34-0.47), P2Y12 inhibitors (OR 0.50, 95% CI 0.45-0.54), β-blockers (OR 0.81, 95% CI 0.76-0.89), and statins (OR 0.70, 95% CI 0.63-0.76) or undergo percutaneous coronary interventions (OR 0.38, 95% CI 0.35-0.42). Crude in-hospital mortality of patients with LBBB was 16.2% versus 6.5% for patients with STE, but adjusted OR was 1.07 (95% CI 0.93-1.24). Mortality of LBBB patients decreased from 22.6% in 1997-2001 to 11.9% in 2012-2016.

Acute myocardial infarction patients with new or presumed new LBBB presence are at high risk of morbidity and mortality. They were treated less aggressively, and although mortality has halved during the last 20 years, there may be room for further improvement. Additional studies are needed to better identify those patients with LBBB who may maximally benefit from an early invasive treatment strategy.