Sequential pulse defibrillation in humans: Orthogonal sequential pulse defibrillation with epicardial electrodes

AbstractA newly described sequential pulse technique, using four mesh electrodes positioned to approximate a true orthogonal system around the heart, was compared with a single pulse system using two or these same electrodes, which were located in positions (hat would be used for an automatic implantable defibrillator. The influence of electrode size was also assessed. The minimal energy necessary for defibrillation (defibrillation threshold) was determined inlraoperatively in 21 volunteer patients undergoing accessory pathway ablation of Wolff-Parkinson-White syndrome. Ventricular fibrillation was induced with alternating current. Ten seconds after fibrillation onset defibrillation shocks were begun using either the single or the sequential pulse technique with stored voltage incremented until defibrillation was accomplished (de-fibrillation threshold). Selection of the use of a single or sequential pulse technique for the initial attempt was randomized.Defibrillation thresholds were determined in three groups of patients: I) those with four small mesh electrodes (6 cm2), 2) those with two small and two large (13 cm2) mesh electrodes, and 3) those with four large mesh electrodes. In all cases, the average minimal energy needed for sequential pulse defibrillation was less than that required for single pulse defibrillation in the same patients with the same electrodes (four small, 24. 8 ± 24. 7 J single versus 6. 7 ± 8. 3 J sequential; two small plus two large, 11. 4 ± 15. 0 J single versus 2. 7 ± 1. 4 J sequential; four large, 8. 1 ± 5. 3 J single versus 3. 9 ± 2. 6 J sequential). Using the 6 cm2electrodes for single pulse defibrillation energies delivered at >45 J in two patients failed to defibrillate the heart. In addition, when at least one large mesh electrode was used for the sequential pulse system, the maximal defibrillalion threshold was 9. 25 J (range 1. 08 to 9. 25).In conclusion, orthogonal sequential pulse shocks provided significant reductions in defibrillation threshold over single pulse shocks regardless of mesh electrode size. In addition, optimal defibrillation required at least one large mesh electrode per pair for both the four patch and the two patch systems