Atrial depolarization electrocardiographic features during orthodromic atrioventricular reciprocating tachycardia mediated by right-sided accessory pathway in the dog

Abstract

Introduction/objectives: Electrocardiographic features of atrial depolarization (AD) during orthodromic atrioventricular reciprocating tachycardia (OAVRT) have been widely studied to localize accessory pathways (APs) in humans. The aim of this study was to determine whether AD characteristics might also be used to determine AP anatomical sites in dogs.

Animals, materials and methods: Clinical records of 83 dogs that underwent electrophysiologic studies for AP ablation were retrospectively analyzed. Accessory pathways were classified into three groups according to localization: right anterior (RA, 13.3%), right postero-septal (RPS, 36.1%), and right posterior (RP, 50.6%). Electrocardiographic characteristics of AD (duration, amplitude, and axis) and OAVRT (AD-AD, peak of R wave - atrial depolarization (R-AD)/atrial depolarization - peak of R wave (AD-R), peak to peak of R wave (RR) interval, and QT duration) were analyzed in all 12 leads.

Results: Mean AD duration in RA, RPS, and RP was 48.0 ± 10.3 ms, 46.1 ± 10.6 ms, and 47.1 ± 10.2 ms, respectively, and the mean amplitude was -0.25 ± 0.12 mV, -0.28 ± 0.20 mV, and -0.28 ± 0.18 mV, respectively. The median electrical axis on the frontal plane was -90.0° (interquartile range [IQR]: 26.5° in RA, 9.4° in RPS, and 13.9° in RP). The median AD-R, mean R-AD intervals, and mean R-AD/AD-R were 140.0 ms (IQR: 34.5 ms), 72.0 ± 19.3 ms, and 0.50 ± 0.14 in RA; 138.0 ms (IQR: 33.0 ms), 76.5 ± 13.6 ms, and 0.55 ± 0.15 in RPS; and 121.0 ms (IQR: 20.0 ms), 74.1 ± 11.7 ms, and 0.59 ± 0.15 in RP. No other statistically significant differences in electrocardiographic parameters were found.

Study limitations: Identification of ADs in some dogs was not straightforward, and thoracic conformation differences may have affected AD measurements.

Conclusions: Electrocardiographic features of AD during OAVRT are not useful for localizing right-sided APs in dogs.

Keywords: Concealed conduction; Electrocardiogram; Electrophysiology; Retrograde conduction; Supraventricular tachycardia.