Intravenous solid tip lead placement in telemetry implanted dogs. Part 1: Surgical methods, signal quality, and pathological endpoints.

Introduction: Electrocardiogram (ECG) signals in safety pharmacology studies are generally collected via subcutaneous or epicardial leads. Subcutaneous placement is an easier procedure, but signals often contain artifacts. Epicardial leads offer improved quality but require additional surgical expertise. Signal quality and tolerability of intravenous (IV)/diaphragmatic ECG leads were investigated as a less invasive alternative to the epicardial ECG lead approach for cardiovascular assessment in dogs.

Methods: Twenty-eight beagle dogs were implanted with PCT (n=14) or PCTP (n=14) transmitters with IV (negative)/diaphragmatic (positive) ECG leads arranged in approximate Lead II configuration. Surgical time for previous epicardial and current IV lead placement approaches was compared. The ECG signals were assessed for up to 32 weeks post-surgery. Signal quality was assessed based on good wave/total wave (GW/TW) ratios calculated using ECG PRO (Ponemah Physiology Platform, Version 4.8) and variability in ECG parameter measurements for each surgical model. Clinical pathology was assessed on all animals before surgery and approximately 2 and 12 weeks post-surgery. A specialized necropsy was conducted on four animals (two PCT and two PCTP) to assess the tolerability of telemetry equipment; selected tissues were examined microscopically.

Results: Surgical time using the IV lead method was approximately 18% shorter than the epicardial lead method. The GW/TW ratio for IV lead-implanted dogs indicated good durability of signal that was similar to epicardial leads. Intra- and inter-animal variability in ECG parameter measurements was similar between IV lead-implanted and epicardial lead-implanted dogs. Clinical pathology revealed no noteworthy findings, and the IV/diaphragmatic surgical approach had minimal consequences on local vasculature and associated implantation sites.

Discussion: Advantages of the IV/diaphragmatic lead model include a less invasive and shorter surgical procedure; high tissue tolerance, ECG signal quality, and durability; and data processing procedures similar to that of epicardial leads. Therefore, the IV/diaphragmatic lead configuration is a viable alternative to more invasive surgical approaches for telemetry device implantation in dogs.