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Temporal stability of defibrillation thresholds with an active pectoral lead system
M R Olsovsky1, M A Pelini, S R Shorofsky
1Department of Medicine, University of Maryland School of Medicine, Baltimore 21201, USA.
Introduction:
Monophasic defibrillation thresholds rise over time with a variety of lead systems. These chronic changes are attenuated or eliminated by biphasic waveforms, although the effect appears dependent upon the lead system. With the downsizing of pulse generator size to allow for routine pectoral implantation, active can lead systems have now become standard. However, the temporal stability of such lead systems has not been evaluated previously.
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 follow-up of 50 days in 46 patients with a uniform testing protocol and shock 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 J predischarge, and 7.6+/-5.5 J at follow-up (ANOVA, P = 0.007). Moreover, only two patients developed an increased threshold > 5 J, and no patient had an inadequate safety 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 defibrillation threshold testing.