ECG Diagnosis: Acute Myocardial Infarction in a Ventricular-Paced Rhythm

In the Emergency Department, the diagnosis of acute myocardial infarction (AMI) relies initially on a patient’s history and the 12-lead electrocardiogram (ECG). Establishing the diagnosis of AMI in the setting of a ventricular-paced rhythm (VPR) is difficult and can result in delay of definitive treatment. In 1996, Sgarbossa et al1 published a retrospective study comparing 17 ventricular-paced ECG controls with 17 ventricular-paced ECGs with AMI, confirmed by cardiac biomarkers. The authors found 3 ECG criteria to evaluate for AMI in patients with VPR: 1) ST-segment elevation (STE) greater than or equal to 1 mm for leads with a positive (concordant) QRS complex; 2) ST-segment depression (STD) greater than or equal to 1 mm in leads V1, V2, or V3; and 3) STE greater than or equal to 5 mm in leads with negative (discordant) QRS complexes. These criteria were identical to the criteria Sgarbossa developed to identify AMI in patients with left bundle branch block (LBBB), except the point scoring system was not used when the criteria were applied to patients with VPRs (Figure 1). Only 1 criterion had both relatively high specificity and statistical significance for the diagnosis of AMI at admission in patients with VPRs: STE greater than or equal to 5 mm in leads with a negative QRS complex. We report a case of an 81-year-old woman with a VPR who presented with chest pain, STE greater than or equal to 5 mm in leads with discordant QRS complexes, STE greater than or equal to 1 mm in a lead with concordant QRS complex, and was diagnosed with an AMI on cardiac catheterization. This case demonstrates the utility of Sgarbossa criteria for detecting AMI in patients with a VPR.Open in a separate window Figure 1 Sgarbossa criteria for acute myocardial infarction in the left bundle branch block. Arrows depict elevation or depression of the ST segment. Reprinted with permission from Cai Q, Mehta N, Sgarossa EB, et al. The left bundle-branch block puzzle in the 2013 ST-elevation myocardial infarction guideline: From falsely declaring emergency to denying reperfusion in a high-risk population. Are the Sgarbossa Criteria ready for prime time? Am Heart J 2013 Sep;166(3):409–13.