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CLINICAL STUDY

Temporal decline in defibrillation thresholds with an active pectoral lead system

^a Division of Cardiology, University of Maryland School of Medicine, Baltimore, Maryland, USA

Manuscript received November 7, 2000; revised manuscript received May 29, 2001, accepted June 15, 2001.

Reprint requests and correspondence: Dr. Eric J. Rashba, University of Maryland School of Medicine, Division of Cardiology, 22 South Greene Street, Room N3W77, Baltimore, Maryland 21201-1595
erashba{at}medicine.umaryland.edu

OBJECTIVES

The objective of this study was to characterize temporal changes in defibrillation thresholds (DFTs) after implantation with an active pectoral, dual-coil transvenous lead system.

BACKGROUND

Ventricular 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.

METHODS

This 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.

RESULTS

The 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.

CONCLUSIONS

The 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.

Abbreviations and Acronyms   ANOVA = analysis of variance   DFT = defibrillation threshold   ICD = implantable cardioverter-defibrillator

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