Uncovering the Septal Q Wave and Other Electrocardiographic Changes in Pediatric Patients With Pre-Excitation Before and After Ablation

In patients with pre-excitation, a short PR interval and a delta wave are not always clearly seen, particularly if the pre-excitation is mild. Absent septal Q waves have been used as additional evidence suggestive of pre-excitation. The purpose of the present study was to determine the incidence of normalization of septal Q waves after successful ablation of a manifest accessory pathway in pediatric patients with normal hearts. We performed a retrospective review of electrocardiograms (ECGs) obtained before and after successful catheter ablation of a single manifest accessory pathway in patients <21 years old (84 pairs of ECGs). The ECGs obtained in patients before ablation for atrioventricular nodal re-entry tachycardia were used as controls (n = 62). The absence of Q waves in the lateral leads (V₅ to V₇) and inferior leads (II, III, aVF) were determined. p Values <0.05 were considered significant. Before the ablation, 72 ECGs (85%) demonstrated absent Q waves in the lateral leads, and only 17 (20%) did not show evidence of Q waves after successful ablation of the accessory pathway (p <0.001). On the inferior leads, 37 ECGs (44%) showed no evidence of Q waves before ablation compared to 24 (29%) after ablation (p <0.05). The findings on the postablation ECG were not statistically different from the findings on the ECGs of the control patients. In conclusion, Q waves in the lateral and inferior leads are often absent in patients with manifest pre-excitation. Absent septal Q waves in the lateral and inferior leads frequently normalize after successful ablation of an accessory pathway.