TEMPORAL STABILITY OF DEFIBRILLATION THRESHOLDS WITH AN ACTIVE PECTORAL LEAD SYSTEM

Stability of Defibrillation Thresholds, Introduction: Monophasic defib rillation thresholds rise over time with a variety of lead systems, Th ese chronic changes are attenuated or eliminated bg biphasic waveforms , although the effect appears dependent upon the lead system, With the downsizing of pulse generates size to allow for routine pectoral impl antation, active can lead systems have now become standard, However, t he temporal stability off such lead systems has not been evaluated pre viously. Methods and Results: This study was a prospective assessment of the changes of active pectoral defibrillation thresholds over time, Thresholds were measured at implant, predischarge, and at a mean foll ow-up of 50 days in 46 patients with a uniform testing protocol and sh ock polarity, The lead system was a dual-coil Endotak DSP lead with an active pectoral pulse generator. Defibrillation thresholds were 9.9 /- 5.5 J at implantation, 8.5 +/- 6.0 g predischarge, and 7.6 +/- 5.5 J at follow-up (ANOVA, P = 0.007). Moreover, only two patients develop ed an increased threshold > 5 J, and no patient had an inadequate safe ty margin at follow-up. Conclusion: These results indicate that active pectoral defibrillation thresholds are stable over the first 2 months postimplantation and question the need for routine serial defibrillat ion threshold testing.