Multicenter transvenous pacemaker implantation in 595 dogs: complications and survival rates

INTRODUCTION/OBJECTIVES: Transvenous pacemakers are routinely used for pathologic bradyarrhythmias including third-degree atrioventricular block (3AVB), sick sinus syndrome (SSS), high-grade second-degree atrioventricular block (2AVB), and atrial standstill (AS). This study reports the multi-institutional complications and survival rates in a large cohort of dogs. ANIMALS, MATERIALS AND METHODS: A retrospective analysis of outcomes and complications in dogs that underwent transvenous pacemaker implantation between January 2000 and December 2016 at four academic institutions was conducted. RESULTS: In total, 595 dogs were identified (221 males and 374 females) with a median age of 10.1 years (range: 0.3-17.0 years). Presenting arrhythmias included 3AVB (54.5%), SSS (24.4%), high-grade 2AVB (16.1%), and AS (4.0%). Major complications occurred in 17.5% (104/595) of cases including lead dislodgement (n = 39), infection (n = 24), thrombus formation (n = 19), ventricular fibrillation (n = 8), cardiac arrest (n = 6), cardiac perforation (n = 5), and iatrogenic tricuspid stenosis (n = 3). Ventricular lead dislodgement in AS (20%) occurred more frequently than SSS (1.4%; P=0.002), and 80% of the ventricular leads that dislodged in dogs with AS were passive leads. Procedural mortality rate was 0.8% (5/595). Median survival time was 2.8 years (2AVB, 2.9 years; 3AVB, 2.9 years; AS, 3.3 years; SSS, 2.5 years). Cardiac mortality occurred in 60.0% of AS cases compared to 2AVB (25.0%), 3AVB (21.9%), and SSS (16.9%). STUDY LIMITATIONS: Limitations of this study included the retrospective nature of the project with some loss to follow-up. CONCLUSIONS: Pacemakers have a low procedural mortality rate, and overall, complications were minimal. Type of lead and underlying disease process may impact the risk of lead dislodgement. Dogs with AS are more likely to die from cardiac-related disease.