Electrocardiographic patterns of ventricular pre-excitation in the dogs with right-sided accessory pathways

Introduction: The aim of the study was to describe the electrocardiographic features of ventricular pre-excitation (VPE) patterns in dogs with right-sided accessory pathways. Animals, materials and methods: Twenty-six dogs with confirmed accessory pathway (AP) via electrophysiological mapping were included in the study. The following parameters were determined: P-δQRS interval, δQRS duration, δQRS axis, δQRS morphology, δ-wave polarity, Q-wave, R-wave, R’-wave, S-wave amplitude and R/S ratio. Results: : The median δQRS complex axis in the frontal plane was: + 68° (IQR 52.5) for right anterior APs, - 24 ° (IQR 24) for right postero-septal APs, - 43.5 ° (IQR 27.25) for right posterior APs (P = 0.007). In lead I, R wave was overall taller in right posterior APs (P = 0.04) for differences among medians within groups, and R’ wave in lead II and in lead III was significantly taller in right anterior Aps (respectively P = 0.02 and P = 0.01) for differences among medians within groups. In precordial leads of all dogs, R/S was 1 in all leads from V2 to V6. Surface electrocardiogram can be used to distinguish right anterior APs from right posterior and right postero-septal ahead of an invasive electrophysiological study.