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

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.

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.

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.

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.