Atrial‐Based Pacing for Sinus Node Dysfunction in Dogs: Initial Results

Background An important consideration for the treatment of sick sinus syndrome ( SSS ) lies in the function of the atrioventricular ( AV ) node because most patients with SSS retain the ability to conduct atrial impulses. Hypothesis/Objectives This retrospective study examined the feasibility of atrial pacing ( AAI ) in dogs with sinus node dysfunction ( SND ). Animals Sixteen dogs with SND and AAI pacing were identified. Methods Retrospective review of medical records. Results Follow‐up time ranged from 45 to 1,227 days (mean: 292 days). Only 1 dog developed AV block 3 days postoperatively. Complete lead dislodgment occurred in 3/16 dogs 1, 19, and 27 days postoperatively. Lead perforation into the pericardial space occurred in 2/16 dogs. Rising thresholds for pacing with possible lead microdislodgment or fibrosis were suspected in another 3/16 dogs 57, 192, and 1,016 days after implantation. None of these dogs had complete loss of capture but all required higher thresholds for pacing. Conclusions and Clinical Importance Based on this small group of dogs, clinically important AV block does not appear to occur in the long‐term for dogs with SND . Risks of lead perforation, complete dislodgment, and rising thresholds for pacing, possibly because of microdislodgment, may be related to the initial skill level of the operator or the leads that were used. Use of leads with reduced torque at the lead tip, higher flexibility, increased lead‐tip surface of contact with the endocardium or, more likely, use of alternate locations for pacing in the small right atrium of dogs with SND may decrease the frequency of these complications.