Atrial defibrillation thresholds of electrode configurations available to an atrioventricular defibrillator

introduction: Little investigation has been conducted to assess the atrial defibrillation thresholds of electrode configurations using electrodes desi gned for internal ventricular defibrillation (right ventricle [RV], superio r vena cava [SVC], and pulse generator housing [Can]) combined with coronar y sinus (CS) electrodes. We hypothesized that a CS --> SVC+Can electrode co nfiguration would have a lower atrial defibrillation threshold than a stand ard configuration for defibrillation, RV --> SVC+Can. We also tested the at rial defibrillation thresholds of five other configurations. Methods and Results: In 12 closed chest sheep, we situated a two-coil (RV, SVC) defibrillation catheter, a left-pectoral subcutaneous Can, and a CS le ad. Atrial fibrillation was burst induced and maintained with continuous in fusion of intrapericardial acetyl-beta -methylcholine chloride. Using fixed -tilt biphasic shocks, we determined the atrial defibrillation thresholds o f seven test configurations in random order according to a multiple-reversa l protocol. The peak voltage and delivered energy atrial defibrillation thr esholds of CS --> SVC+Can (168 +/- 67 V, 2.68 +/- 2.40 J) were significantl y lower than those of RV --> SVC+Can (215 +/- 88 V, 4.46 +/- 3.40 J). The a trial defibrillation thresholds of the other test configurations were RV+CS --> SVC+Can: 146 +/- 59 V, 1.92 +/- 1.45 J; RV --> CS+SVC+Can: 191 +/- 89 V, 3.53 +/- 3.19 J; CS --> SVC: 188 +/- 98 V, 3.77 +/- 4.14 J; SVC --> CSCan: 265 +/- 145 V, 7.37 +/- 9.12 J; and SVC --> Can: 516 +/- 209 V, 24.5 /- 15.0 J. Conclusions: The atrial defibrillation threshold of CS --> SVC+Can is signi ficantly lower than that of RV --> SVC+Can. In addition, the low atrial def ibrillation threshold of RV+CS --> SVC+Can merits further investigation. Ba sed on corroboration of low atrial defibrillation thresholds of CS-based co nfigurations in humans, physicians might consider using CS leads with atrio ventricular defibrillators.