title: 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 atrioventricular (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 transvenous application of this approach.
mesh_terms: D000818:Animals; D002036:Bundle of His / Q000502:physiology*; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004285:Dogs; D004562:Electrocardiography; D004567:Electrodes, Implanted; D004867:Equipment Design; D006346:Heart Septum; D007495:Iridium; D010984:Platinum; D011140:Polyurethanes; D011690:Purkinje Fibers / Q000502:physiology*
chemical_list: D011140:Polyurethanes; D007495:Iridium; D010984:Platinum