Septal His‐Purkinje Ventricular Pacing in Canines: A New Endocardial Electrode Approach

Abstract

Ventricular activation sequences and cardiac performance are influenced by pacing sites. Stimulation of or close to the specialized a trioventricular (AV) conduction system optimizes paced ventricular function compared to alternative epi- or endocardial muscle conduction sites. This study reports a new endocardial electrode implant approach to approximate septal His-Purkinje ventricular pacing. Five 6-month-old beagles were used, A custom, platinum-iridium, exposed helical screw electrode (Medtronic, Inc.), 4.5-mm long, with a 17.8-mm² surface area, was designed with a polyurethane covered 4 filar MP35N nickle conductor lead. An 8 French sheath (USCI, Inc.) was modified as introducer to permit simultaneous implant intracardiac pressure and electrogram recordings. Following a thoracotomy, the introducer was inserted through the right atrial appendage and advanced to record optimal His-bundle electrogram while maintaining atrial pressure along the septal tricuspid valve annulus. After electrode implant, ECG demonstrated narrow paced QRS morphology. Mean implant values showed sensed R wave 6,3 mV, slew rate 0.65 V/sec, pacing impedance 319 ohms, and threshold 0.9 V/3.3 mA at 0.5-msec output. Necropsy showed implant above the tricuspid annulus with electrode extension into and contained within the proximal ventricular septum. This study demonstrates that an endocardial septal approach to His-Purkinje ventricular pacing to optimize paced ventricular function is feasible with a new electrode design and precise septal implant technique. Alternative introducer designs may permit tranvenous application of this approach.