ROLE OF PROXIMAL ELECTRODE POSITION IN TRANSVENOUS VENTRICULAR DEFIBRILLATION

Transvenous defibrillation lead systems have been demonstrated to redu ce operative morbidity and mortality associated with implantation of c ardioverter-defibrillators. To determine the best position for the pro ximal electrode in transvenous systems, defibrillation thresholds were compared for three positions in a single-pathway, two-lead system. Tw o defibrillation lead electrodes were transvenously inserted into seve n dogs. The distal electrode was positioned in the right ventricular a pex. The proximal electrode was randomized to one of three positions: (1) the superior (cranial) vena cava (SVC) at the junction of the righ t atrium, (2) the left innominate vein at the junction of the SVC, or (3) the external jugular vein. Biphasic defibrillation thresholds for converting electrically induced ventricular fibrillation were determin ed for the three positions of the proximal electrode in each dog. The innominate vein position resulted in the lowest defibrillation thresho ld (555 +/- 123 V) as compared to the SVC (640 +/- 126 V; p = 0.0612) and the jugular vein (709 +/- 117 V; p = 0.0013). Lead impedance gradu ally increased with increasing distance between the two shocking elect rodes: 58.4 +/- 11.4 Omega for SVC, 76.2 +/- 13.8 Omega for innominate vein, and 94.9 +/- 10.2 Omega for jugular vein proximal lead electrod e position (p < 0.05 for all pairwise comparisons). In two-electrode t ransvenous defibrillation lead systems, positioning the proximal elect rode in the left innominate vein produced the lowest defibrillation th reshold.