Atrial defibrillation with transvenous lead : randomized comparison of active can shocking pathways

OBJECTIVES The purpose of this study was to compare transvenous atrial defibrillation thresholds with lead configurations consisting of an active left pectoral electrode and either single or dual transvenous coils. BACKGROUND Low atrial defibrillation thresholds are achieved using complex lead systems including coils in the coronary sinus. However, the efficacy of more simple ventricular defibrillation leads with active pectoral pulse generators to defibrillate atrial fibrillation (AF) is unknown. METHODS This study was prospective, randomized assessment of shock configuration on atrial defibrillation thresholds in 32 patients. The lead system was dual coil Endotak DSP lead with left pectoral pulse generator emulator. Shocks were delivered either between the right ventricular coil and an active can in common with the proximal atrial coil (triad) or between the atrial coil and active can (transatrial). RESULTS Delivered energy at defibrillation threshold was 7.1 ± 6.0 J in the transatrial configuration and 4.0 ± 4.2 J in the triad configuration (p < 0.005). Moreover, low threshold (≤3 J) was observed in 69% of subjects in the triad configuration but only 47% in the transatrial configuration. Peak voltage and shock impedance were also lowered significantly in the triad configuration. Left atrial size was the only clinical predictor of the defibrillation theshold (r = 0.57, p < 0.002). CONCLUSIONS These results indicate that low atrial defibrillation thresholds can be achieved using single-pass transvenous ventricular defibrillation lead with conventional ventricular defibrillation pathway. These dat support the development of the combined atrial and ventricular defibrillator system.