The use of Smith-modified Sgarbossa criteria to diagnose an extensive anterior acute myocardial infarction in a patient presenting with a left bundle branch block.

Patients with LBBB of unknown onset presenting with chest pain can pose a diagnostic challenge in the ED while Smith-Modified-Sgarbossa (SMS) ECG criteria might facilitate AMI diagnosis. We demonstrate a case of a 79-year-old man that presented to the ED with chest pain. Original Sgarbossa criteria were negative for AMI while SMS criteria were applied showing proportionally excessive discordance between ST-segment and preceding S-wave thus fulfilling diagnostic criterion for AMI. The coronary angiogram showed the total occlusion of the culprit left anterior descending artery. In this case, awareness of SMS criteria aided in the early prehospital diagnosis of AMI in the setting of LBBB and impacted the course of treatment.