title: Temporal stability of defibrillation thresholds with an active pectoral lead system.
abstract: BACKGROUND
  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.
  
  
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Medicine, University of Maryland School of Medicine, Baltimore 21201, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Olsovsky
authors.forename: M A
authors.initials: MA
authors.lastname: Pelini
authors.forename: S R
authors.initials: SR
authors.lastname: Shorofsky
authors.forename: M R
authors.initials: MR
authors.lastname: Gold
mesh_terms: D000368:Aged; D001145:Arrhythmias, Cardiac / Q000628:therapy*; D017147:Defibrillators, Implantable; D004554:Electric Countershock / Q000295:instrumentation*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies