Abstract: Background- Transvenous pacemakers are routinely used for pathologic bradycardias including 3rd degree AV block (3AVB), Sick Sinus Syndrome (SSS), high grade 2nd degree AV block (2AVB), and atrial standstill (AS). Objectives- This study reports the multi-institutional complications and survival rates in a large cohort of dogs. Animals- Dogs presenting for transvenous pacemaker implantation between January 2000 and December 2016 at four academic institutions. Methods- A retrospective analysis of outcomes and complications in dogs who underwent transvenous pacemaker implantation. Results- 595 dogs were identified (221 male; 374 female) with a median age of 9.6 years (range, 0.27-17 years). Presenting arrhythmias included 3AVB (54.5%), SSS (24%), high grade 2AVB (16.1%), and AS (3.9%). Major complications occurred in 17% (105/595) of cases including lead dislodgement (n=39), infection (n=25), thrombus formation (n=19), ventricular fibrillation (n=8), cardiac arrest (n=6), cardiac perforation (n=5), and iatrogenic tricuspid stenosis (n=3). Procedural mortality rate was 0.8% (5/595). The rate of ventricular lead dislodgement was 24% in AS, 8% in 3AVB, 2% in 2AVB, and 1% in SSS. The rate of dislodgement in active ventricular leads was 10% and 4% in passive leads. Overall median survival time was 38.7 months (2AVB, 43.9 months; 3AVB, 43.3 months; AS, 40.4 months; SSS, 34.8 months). Cardiac mortality occurred in 75% of AS compared to 2AVB (30%), 3AVB (27%), and SSS (19%). Conclusions- There is a high procedural success rate with low procedural mortality rate. Overall, complications were minimal. Type of lead and underlying disease process may impact the risk of lead dislodgement.
