Detecting acute ST-segment elevation myocardial infarction (STEMI) in the setting of left bundle branch block (LBBB) remains a challenge to clinicians. Several diagnostic and triage algorithms have been proposed to accurately identify LBBB patients with an acute culprit vessel. We aimed to validate the algorithm proposed by Cai et al., which uses patients' hemodynamic status and the modified Sgarbossa electrocardiography criteria to guide reperfusion therapy.

This retrospective study was performed with a chart review in emergency departments (EDs) of 2 medical centers, 2 regional hospitals, and 1 local hospital. From January 2010 to December 2014, 2432 consecutive patients were diagnosed as having STEMI in the ED, including 65 patients with LBBB (2.6%).

The patients with LBBB were older and more frequently presented with acute pulmonary edema (58.5% vs 22.1%, p < 0.001), cardiogenic shock (16.9% vs 6.3% p = 0.006), and VT/VF episodes (7.7% vs 2.2%, p = 0.034) and had a higher 30-day mortality rate (20.0% vs 10.4% p = 0.032) than those without LBBB. We then tested the algorithm proposed by Cai et al. and noted a sensitivity of 93.8% in identifying a culprit lesion.

The inconsistency of the guideline recommendations reflects the uncertainty of diagnostic and therapeutic strategies and the pressing need for tools to accurately identify the true acute myocardial infarction in patients presenting with chest pain and LBBB. The algorithm proposed by Cai et al. had good sensitivity and would allow emergency physicians to implement the timely treatment protocol for this high-risk population.