R-peak time in clinically healthy dogs with different thoracic conformations.

R-peak time (RPT) is an electrocardiographic parameter that represents the time taken for electrical activation to spread from the endocardium to the epicardium. In human medicine, right ventricular RPT is measured from lead V1 to lead V2, and left ventricular RPT from lead V5 to lead V6. The aim of the present study was to define RPT duration in a group of clinically healthy dogs with different thoracic conformations. Sixty clinically healthy dogs underwent a 12-lead electrocardiogram recorded using a previously described precordial system. The dogs were allocated into three morphologic groups. In the brachymorphic group, the median and 25th-75th percentiles for RPT in V1 were 10.5 ms (10-12 ms); V2, 18 ms (16.5-20 ms); V3, 19 ms (18-22 ms); V4, 20 ms (17-23.5 ms); V5, 21 ms (18.5-24 ms); and V6: 22 ms (18.5-25.5 ms). In the mesomorphic group, RPT in V1 was 16 ms (14-18 ms); V2, 22 ms (20-24 ms); V3, 23 ms (21-25 ms); V4, 23 ms (22-25 ms); V5, 25 ms (23-27 ms); and V6, 28 ms (25-30 ms). In the dolichomorphic group, RPT in V1 was 15 ms (13-17 ms); V2, 29 ms (26-32.5 ms); V3, 30 ms (27-33.5 ms); V4, 29.5 ms (26-35 ms); V5, 30 ms (28-34 ms); and V6, 31.5 ms (28-35 ms). RPT in V1 was significantly shorter than RPT in V2 to V6 in all morphotypes (P < 0.05). In all precordial leads, RPT was significantly different between morphotypes (P < 0.05). These results are in agreement with previous findings in humans and with the observation that V1 reads the right ventricle and V2 to V6 read the left ventricle. These preliminary data provide RPT ranges in clinically healthy dogs of different morphotypes.

Radiofrequency catheter ablation of accessory pathways in the dog: the Italian experience (2008-2016).

INTRODUCTION: Accessory pathways (APs) in dogs are mostly right-sided, display nondecremental conduction, and mediate atrioventricular reciprocating tachycardias (AVRTs). Radiofrequency catheter ablation (RFCA) is considered the first-line therapy in human patients to abolish electrical conduction along APs. ANIMALS: Seventy-six consecutive client-owned dogs. MATERIAL AND METHODS: Retrospective study to describe the precise anatomical distribution and the electrophysiologic characteristics of APs in a large population of dogs and to evaluate long-term success and complication rates of RFCA. RESULTS: Eighty-three APs were identified in 76 dogs (92.1% with single APs and 7.9% with multiple APs); 96.4% were right-sided, 3.6% left-sided. Conduction along the APs was unidirectional and retrograde in 68.7% of the cases and bidirectional in 31.3%. Accessory pathways presented retrograde decremental properties in 6.5% of the cases. They mediated orthodromic AVRT in 92.1% of the cases and permanent junctional reciprocating tachycardia in 6.5%. In one case, no AVRT could be induced. In 97.4% of dogs, RFCA was attempted with an acute success rate of 100%. In 7.7% of cases, recurrence of the tachycardia occurred within 18 months, followed by a second definitively successful ablation. A major complication requiring pacemaker implantation was identified in 2.6% of dogs. DISCUSSION: Accessory pathway distribution and electrophysiologic properties in these 76 dogs were similar to previous report. Long-term success and complication rates of RFCA in dogs appeared very similar to results of humans. CONCLUSION: Radiofrequency catheter ablation of APs can be performed with a high success rate and low incidence of complications.