Transvenous defibrillation leads: is there an ideal position of the defibrillation anode?

A potential benefit of two-lead transvenous defibrillation systems is the ability to independently position the defibrillation electrodes, changing the vector field and possibly decreasing the DFT. Using the new two-lead transvenous TVL lead system, we studied whether DFT is influenced by SVC lead position and whether there is an optimal position. TVL leads and Cadence pulse generators were implanted in 24 patients. No intraoperative or perioperative complications were observed. In each patient, the DFTs were determined for three SVC electrode positions, which were tested in random order: the brachiocephalic vein, the mid-RA, and the RA-SVC junction. The mean DFTs in the three positions were not statistically different, nor was any single lead position consistently associated with lower DFTs. However, an optimal electrode position was identified in 83% of patients, and the DFT from the best lead position for each patient was significantly lower than for any one of the electrode positions (P < 0.01). The mean safety margin for the best SVC lead position was approximately 27 J. These results demonstrate the advantage of a two-lead system, as well as the importance of testing multiple SVC lead positions when the patient's condition permits. Both of these factors can decrease the DFT and maximize the defibrillation safety margin. This will become increasingly important as pulse generator capacitors become smaller (as part of the effort to decrease generator size) and the energy output of the generators consequently decreases.