Transvenous pacemaker implantation is the definitive treatment for pathologic bradyarrhythmias, though reported complication rates have historically been high. The purpose of this study was to determine survival times and complication rates for dogs who underwent transvenous pacemaker implantation in a large number of institutions. In addition, we wished to identify factors that may predispose patients to the development of complications.
A multicenter retrospective analysis of dogs who underwent transvenous pacemaker implantation between January 1st, 2000 and December 31st, 2016 was performed. Arrhythmia type, generator location, number of leads, complication rate and survival times were evaluated. Complications were categorized as major versus minor and by time to development. Survival time was evaluated by Kaplan-Meyer curve.
In total, 595 dogs were identified (221 male, 186 neutered; 374 female, 349 spayed) with a median age of 9.63 years (range, 0.27-17 years). Presenting arrhythmias included 3rd degree AV block (3AVB) (n=324, 54.5%), Sick Sinus Syndrome (SSS) (n=143, 24%), high grade 2nd degree AV block (2AVB) (n=96, 16.1%), atrial standstill (AS) (n=23, 3.9%), or miscellaneous (n=9, 1.5%). Six hundred and three pacemaker implantations were performed with 601 (99.7%) cases surviving the intraoperative period. Patients received single chamber (n=536, 89.2%), dual chamber (n=34, 5.7%) or VDD (n=31, 5.1%) pacing systems. Both active (n=265, 44.5%) and passive (n=331, 55.5%) ventricular fixation leads were used. Pacemaker generators were placed subcutaneously in the cervical region (n=318, 52.9%), or caudal to the scapula (n=283, 47.1%). A total of 594 cases (98.8%) survived to discharge. Overall median survival time was 38.7 months (2AVB, 43.9 months; 3AVB, 43.3 months; AS, 40.4 months; SSS, 34.8 months). There was a significant difference in survival time between 3AVB and SSS (p = 0.043).
Major complications (n=130, 21.8%) included lead dislodgement (37 episodes), lead perforation (5 episodes), infection (23 episodes), or other significant complications (65 episodes). Seventeen infections involved the generator (13 cervical placements, 4 caudal to the scapula), which approached but did not reach statistical significance (p = 0.055). Minor complications (n=97, 16.3%) included seroma formation (82 episodes) or other minor issues (15 episodes). Pacing complications (n=127, 21.3%) included oversensing (37 episodes), undersensing (25 episodes), intermittent loss of capture (23 episodes), dysfunction requiring a pacing mode switch (18 episodes), noise reversion (13 episodes), or conduction block at high heart rates (5 episodes).
Transvenous pacemaker implantation is associated with a relatively high complication rate. Predisposing factors for specific complications were unable to be identified. 3AVB was associated with a longer survival time compared to SSS, though did not differ from other bradyarrhythmias.
University of Minnesota
Thursday, June 14
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