Terminal QRS distortion is present in anterior myocardial infarction but absent in early repolarization

Abstract

Background: Early repolarization (ER) and acute left anterior descending artery occlusion (LADO) may be difficult to distinguish. Terminal QRS distortion (TQRSD), defined by the absence of both an S wave and J wave in either of leads V₂ or V₃, is often present in anterior ST-segment elevation myocardial infarction. We hypothesized that this finding would always be absent in ER.

Methods: This was a retrospective analysis of electrocardiograms (ECGs) of consecutive patients who presented to the emergency department with ischemic symptoms and had a cardiologist interpretation of "benign ER" on the initial emergency department ECG. All ECGs were scrutinized for the presence of an S wave and a J wave in leads V₂ and V₃. Differences in S-wave amplitudes between complexes with and without J waves were analyzed using nonparametric Mann-Whitney testing and confidence intervals around a proportion.

Results: One hundred seventy-one patients were identified with benign ER. Zero of 171 had TQRSD (specificity for LADO, 100%; 95% confidence interval, 97.8-100). In lead V₂, S waves were absent in only 1 of 171 ECGs; however, in that ECG, a J wave measuring 0.5 mm was present. In lead V₃, S waves were absent in 16 ECGs, but all of these ECGs had J waves. When J waves were absent in leads V₂ or V₃, the corresponding S waves were deeper than S waves in QRS complexes with J waves.

Conclusion: Terminal QRS distortion was never observed in benign ER. Based on previous studies indicating the presence of TQRSD in LADO, it was, thus, 100% specific to LADO when the differential diagnosis was acute myocardial infarction vs ER.