Five-year experience with implantation and follow-up of transvenous implantable cardioverter defibrillators: Placing postimplant defibrillation threshold testing in perspective

Abstract

Background: The rapid technological advancement in transvenous implantable cardioverter defibrillators (ICDs) has resulted in heterogeneous and often controversial approaches to follow-up procedures. The efficacy of postimplantation defibrillation threshold (DFT) testing with new-generation biphasic ICDs is unknown. Objective: In this retrospective study, predischarge and postdischarge DFT protocols were compared to evaluate their safety and effect on adverse clinical events. Methods: The study population consisted of 89 patients with 92 ICDs and 103 endovascular lead systems. Forty-four patients had DFT tests during implant and the predischarge period. Thirty patients had DFT tests during implant and the postdischarge period. Sixteen patients had only implant DFT data available. The follow-up period ranged from 3 days to 5.6 years. Results: Ninety-nine percent of patients had successful implants. Postimplant DFT tests detected potential problems in only 1% of asymptomatic patients. Thirty-six percent of patients with normal predischarge DFT tests had adverse clinical events compared with 18% in the postdischarge group. Patients with postimplant DFTs > 25 joules (J) and safety margins ≥ 10 J had a lower incidence of adverse clinical events (p = 0.03) compared with those with safety margins < 10 J. An 11% malfunction rate was observed in ICD leads during the follow-up period. Conclusions: DFT testing after implant is safe; however, routine postimplant DFT testing has limited value in assessing abnormalities in patients with the current generation of biphasic transvenous ICD devices. A 10-J safety margin was associated with a lower incidence of adverse clinical events in patients with DFTs > 25 J. Endovascular lead failure remains a significant problem with ICD systems requiring vigilant follow-up.