ECG arrhythmias in non-implanted vs. telemetry-implanted dogs: need for screening before and sufficient recovery time after implantation.

Introduction: The purpose of this study was: (1) to characterize and assess the incidence of spontaneous arrhythmias in totally naive Beagle dogs (n=51; 10 males+41 females): (2) to study the effects of permanent ECG- and LVP-probe telemetry implants both acutely and up to 233days after surgery in a subset of 11 female Beagle dogs.

Methods: Naive ECG assessments were conducted by means of 6 external telemetry leads in jacketed dogs. Telemetry ECG recordings were captured by means of implanted telemetry devices suitable for ECG, LVP and aortic blood pressure recording. Experienced laboratory personnel visually evaluated all 22h ECG recordings at different time points after implantation and evaluated the incidence and type of arrhythmia.

Results: The 51 healthy and totally naive Beagle dogs showed a prevalence of: 49.0% 2°AVB; 58.8% single atrial premature complexes; 17.6% junctional tachycardia; 27.5% ventricular complexes; 13.7% ventricular escape complexes; 21.6% ventricular premature complexes; 3.9% runs of ventricular complexes; 3.9% runs of ventricular escape complexes. As such, a high percentage of clinically normal Beagle dogs showed different types of arrhythmias when ECG's obtained by external telemetry leads were fully evaluated for a 22h period. The chronic implantation of a ventricular probe through the apex of the heart in 11 dogs only, resulted in higher incidences and frequencies of ventricular episodes, which (in some dogs) extended up to 8weeks. Eight months after surgery none of the implanted dogs showed ventricular tachycardia and only 10% had single ventricular or ventricular premature complexes at low frequencies.

Discussion: A thorough evaluation of the ECG's of Beagle dogs selected for telemetry implantation can help to avoid inherent arrhythmia-burdened dogs being implanted and used in studies where these arrhythmias will confound drug assessment by increasing the number of potential false positives.