Internal cardiac defibrillation: single and sequential pulses and a variety of lead orientations.

A sequential pulse system for internal cardiac defibrillation incorporating catheter and patch electrodes with two current pathways has been shown to reduce defibrillation threshold in comparison to the single pulse technique. The relative advantage of the sequential pulse over the single pulse technique with other lead systems is not known. We compared defibrillation thresholds using sequential and single pulses delivered to a variety of lead orientations with the same electrode surface areas, when possible. Defibrillation threshold totals determined in halothane-anesthetized open-chest pigs averaged: For the single pulse shock passed between (1) superior vena cava (SVC) and left ventricular apical patch (LVA), 27.2 +/- 9.1 joules (J) and (2) LV epicardial patch (LVE) to right ventricular epicardial (RVE) patch leads, 16.5 +/- 2.1 J; and for the sequential pulse shock with two pulses passed between: (1) the SVC to RV intracavitary apex (RVA) and a quadripolar catheter in the coronary sinus to the RVA, 11.6 +/- 1.0 J; (2) the SVC to LVA and the LVE to RVE, 9.6 +/- 1.3 J and (3) the SVC to RVA and the LVE to RVA, 8.9 +/- 0.4 J. Defibrillation thresholds for sequential pulse shocks were all significantly lower than either of the defibrillation thresholds for single pulse shocks (p less than 0.001). We conclude that the sequential pulse system provides a substantial reduction in defibrillation threshold over the single pulse regardless of the lead system when the surface area and pulse characteristics are controlled. Sequential pulse technique may be valuable in the design of an implantable automatic defibrillator.(ABSTRACT TRUNCATED AT 250 WORDS)