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

IntroductionThe aim of the study was to describe the electrocardiographic features of ventricular pre-excitation (VPE) patterns characterized by the presence of delta (delta) wave, short P-delta QRS interval, wide delta QRS complexes in dogs with right-sided accessory pathways.Animals, materials and methodsTwenty-six dogs with a confirmed accessory pathways (AP) via electrophysiological mapping were included. All dogs underwent a complete physical examination, 12-lead ECG, thoracic radiography, echocardiographic examination and electrophysiologic mapping. The AP were located in the following regions: right anterior, right posteroseptal, right posterior. The following parameters were determined: P-delta QRS interval, delta QRS duration, delta QRS axis, delta QRS morphology, delta-wave polarity, Q-wave, R-wave, R'-wave, S-wave amplitude, and R/S ratio.ResultsIn lead II, the median delta QRS complex duration was 82.4 (IQR 7.2) and the median P-delta QRS interval duration was 54.6 (IQR 4.2) msec. The median delta QRS complex axis in the frontal plane was: + 68 degrees (IQR 52.5) for right anterior APs, - 24 degrees (IQR 24) for right postero-septal APs, - 43.5 degrees (IQR 27.25) for right posterior APs (P = 0.007). In lead II, the polarity of the delta wave was positive in 5/5 right anterior APs and negative in 7/11 postero-septal APs and 8/10 in right posterior APs. In precordial leads of all dogs, R/S was <= 1 in V1 and > 1 in all leads from V2 to V6.ConclusionSurface electrocardiogram can be used to distinguish right anterior APs from right posterior and right postero-septal ahead of an invasive electrophysiological study.