BIPOLAR TRANSVENOUS DEFIBRILLATION - EFFICACY OF 2 DIFFERENT POSITIONS OF THE ANODE

For most nonthoracotomy defibrillation lead systems, the transvenous a node can be positioned independently of the right ventricular (RV) cat hode. Usually a vertical position in the superior vena cava (SVC) is c hosen. However, it is unknown if this position yields the optimal defi brillation threshold (DFT). Therefore, in 15 patients undergoing defib rillator implantation the SVC position was compared in a crossover stu dy design with a horizontal position in the left brachiocephalic vein (BCV), Mean DFT was not different for SVC and BCV (19.2 +/- 9.6j vs 18 .5 +/- 9.1j) but DFT of individual patients differed by up to 22 joule s. A positive correlation between impedance and DFT in the BCV positio n (r = 0.6; P less than or equal to 0.05) indicated that the improved geometry of the defibrillation field with the BCV position is opposed by a higher impedance found for this position (63 +/- 15 Omega vs 52 /- 7 Omega). Thus, defibrillation is not improved in general although individual patients might benefit.