1026-85 Enhanced Defibrillation Efficacy with an Active Pectoral Pulse Generator

An active pectoral pulse generator can be incorporated in a single coil defibrillation lead system to achieve low defibrillation thresholds (DFT). However, the incremental benefit of an active pulse generator with an integrated lead system has not been evaluated. Accordingly, we performed a prospective trial of a 65 cc pulse generator shell with an Endotak lead in 22 consecutive pts undergoing defibrillator implantation. Energy (E) and leading edge voltage (V) at DFT was measured using a step down protocol to first failure with biphasic waveforms (60:40 tilt). Either lead alone (proximal coil = anode) or lead + shell (proximal coil and shell = anode) were tested with paired testing in random order.E(joules)V(volts)R(ohms)Lead alone13.1±6.7395±10549±5Lead + Shell8.5±3.1*319±61*42±4**p<0.001A DFT of≤10J was found in 50% (11/22) of patients with lead alone and 86% (19/22) of patients with lead + shell (p<0.02).In conclusion, adding an active pulse generator to an integrated transvenous lead significantly reduced DFTs and system impedance (R). The consistently low defibrillation energy requirements with the use of an active small pectoral shell, makes the development of a defibrillator with reduced size and lower maximal output feasible

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

AbstractOBJECTIVESThe 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.BACKGROUNDLow 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.METHODSThis study was a prospective, randomized assessment of shock configuration on atrial defibrillation thresholds in 32 patients. The lead system was a dual coil Endotak DSP lead with a 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).RESULTSDelivered 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, a 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).CONCLUSIONSThese results indicate that low atrial defibrillation thresholds can be achieved using a single-pass transvenous ventricular defibrillation lead with a conventional ventricular defibrillation pathway. These data support the development of the combined atrial and ventricular defibrillator system

Temporal decline in defibrillation thresholds with an active pectoral lead system

AbstractOBJECTIVESThe objective of this study was to characterize temporal changes in defibrillation thresholds (DFTs) after implantation with an active pectoral, dual-coil transvenous lead system.BACKGROUNDVentricular DFTs rise over time when monophasic waveforms are used with non-thoracotomy lead systems. This effect is attenuated when biphasic waveforms are used with transvenous lead systems; however, significant increases in DFT still occur in a minority of patients. The long-term stability of DFTs with contemporary active pectoral lead systems is unknown.METHODSThis study was a prospective assessment of temporal changes in DFT using a uniform testing algorithm, shock polarity and dual-coil active pectoral lead system. Thresholds were measured at implantation, before discharge and at long-term follow-up (70 ± 40 weeks) in 50 patients.RESULTSThe DFTs were 9.2 ± 5.4 J at implantation, 8.3 ± 5.8 J before discharge and 6.9 ± 3.6 J at long-term follow-up (p < 0.01 by analysis of variance; p < 0.05 for long-term follow-up vs. at implantation or before discharge). The effect was most marked in a prespecified subgroup with high implant DFTs (≥15 J). No patient developed an inadequate safety margin (<9 J) during follow-up.CONCLUSIONSThe DFTs declined significantly after implantation with an active pectoral, dual-coil transvenous lead system, and no clinically significant increases in DFT were observed. Therefore, routine defibrillation testing may not be required during the first two years after implantation with this lead system, in the absence of a change in the cardiac substrate or treatment with antiarrhythmic drugs

Intravenous amiodarone suppression of electrical storm refractory to chronic oral amiodarone.

We report the case of an electrical storm in a cardiac arrest survivor with an ICD, in whom chronic oral amiodarone failed to suppress ventricular arrhythmias, and in whom intravenous amiodarone resulted in stability for 6 weeks prior to successful cardiac transplantation. Intravenous amiodarone can be successful in suppressing life-threatening ventricular arrhythmias, even when chronic oral amiodarone is unsuccessful