Cardiac pacemakers in dogs: programming parameters

Objective: To report the behavior of the main parameters used in the evaluation of cardiac pacemakers (PMs) in dogs, associated complications, and survival times. Methods: This retrospective cohort study evaluated dogs that received PMs (from 2016 through 2023) at a veterinary teaching hospital. Dogs of various breeds, ages, and sexes with at least 1 baseline assessment were included. The PM parameters pacing threshold amplitude, impedance (or conductance), and estimated battery life were assessed immediately after PM insertion and at reevaluation times (≤ 7, ≤ 90, ≤ 547, ≤ 912, and ≥ 912 days). Complications and survival rates were also evaluated. Results: The median survival time of 11 dogs was 30 months. Two complications were recorded: seroma and suture dehiscence. A reduction in impedance over time was further validated by a significant Skillings-Mack test (χ2 = 12.692; P = .0054). Pacing threshold amplitude and estimated battery life did not significantly change. Conclusions: PM implantation in dogs is safe and eliminates clinical signs. A reduction in myocardial impedance (or increased conductance) is expected, but impedance assessment should consider individual baselines, observing the behavior rather than just the normal range or isolated values. Baseline pacing threshold amplitude also varies between individuals and tends to decrease over time. No significant reduction in estimated battery life was observed during the study period, probably due to high device longevity. Clinical Relevance: This study provides the first data for PM parameters in dogs. The results suggest that clinical interpretation should focus on longitudinal parameter behavior relative to baseline values rather than solely on the reference range.