Optimal electrode position for transvenous defibrillation: prospective randomized study

Objectives. This study was performed to determine the optimal position for the proximal electrode in two-electrode transvenous defibrillation system. Background. Minimizing the energy required to defibrillate the heart has several potential advantages. Despite the increased use of two-electrode transvenous defibrillation systems, the optimal position for the proximal electrode has not been systematically evaluated. Methods. Defibrillation thresholds were determined twice in random sequence in 16 patients undergoing implantation of two-lead transvenous defibrillation system; once with the proximal electrode at the right atrial-superior ven cav junction (superior ven cav position) and once with the proximal electrode in the left subclavian-innominate vein (innominate vein position). Results. The mean (±SD) defibrillation threshold with the proximal electrode in the innominate vein position was significantly lower than with the electrode in the superior ven cav position (13.4 ± 5.7 J vs. 16.3 ± 6.6 J, p = 0.04). Defibrillation threshold with the proximal electrode in the innominate vein position was lower or equal to that achieved in the superior ven cav position in 75% of patients. In patients with normal heart size (cardiothoracic ratio ≤0.55), the improvement in defibrillation threshold with the proximal electrode in the innominate vein position was more significant than in patients with an enlarged heart (innominate vein 13.0 ± 6.5 J vs. superior ven cav 17.9 ± 5.1 J, p < 0.01). In patients with an enlarged heart, no difference between the two sites was observed (innominate vein 13.9 ± 4.5 J vs. superior ven cav 13.6 ± 8.3 J, p = NS). Conclusions. During implantation of two-lead transvenous defibrillation system, positioning the proximal defibrillation electrode in the subclavian-innominate vein will lower defibrillation energy requirements in the majority of patients.