Silent Lead Malfunction Detected Only During Defibrillator Replacement

Abstract

A 54-year-old man with right ventricular (RV) arrhythmogenic dysplasia and episodes of sustained ventricular tachycardia (VT) was admitted at another institution, where he underwent a RV biopsy complicated by an RV perforation and tamponade. A thoracotomy was performed and the RV was sutured. Soon afterward, he developed a superior vena cava syndrome. Several weeks later, a Medtronic GEM 7221 ICD was implanted via a thoracotomy at a left prepectoral site. A Medtronic Transvene RV 6936 tripolar lead (two sensing electrodes, one defibrillation coil, and active fixation) was inserted via the right atrium into the RV apex. The lead was tunneled to the left subclavicular region and connected to the ICD. At implantation, RV pacing/sensing thresholds and RV pacing Address for reprints: Roland Stroobandt, Figure 1. Stored intracardiac electrograms recorded in the sensing electrodes representing the bipolar electrogram between the V tip to V ring (top: 1 mV/2.5 mm) and the shocking electrodes (can to the high-voltage RV coil − HVB = RV coil) at the bottom (1 mV/10 mm). Ventricular fibrillation (VF) was induced by a shock on T-wave of 5 J. VF was appropriately detected (FD) and terminated by a shock of 20 J. After the shock, the device demonstrated oversensing of false signals (arrows) by the sensing electrodes (V tip to V ring) at a sensitivity of 0.3 mV. FD = VF detection; VS = ventricular sense; CE = charge end; CD = cardioversion/defibrillation pulse; VP = ventricular pace; FS = VF sense.lead impedance were normal and the defibrillation threshold was <20 J. Follow-up for several years on amiodarone therapy documented no shocks, but the device recorded episodes of nonsustained VT. No other arrhythmias including oversensing were observed.Seven years postimplantation, the ICD was replaced for battery depletion. The original RV lead exhibited satisfactory parameters: RV pacing threshold was 1.3 V at 0.5 ms, the R-wave amplitude measured 6.9 mV, and the pacing lead impedance was 401 at 5.0 V. As the presence of a superior vena cava syndrome precluded transvenous insertion of a new lead, a Medtronic ICD Maximo VR 7332 Cx was connected to the old Transvene lead. A 20-J test shock was successful in terminating ventricular fibrillation, and the shock impedance measured 40 . Shortly after the shock, false signals were detected on the bipolar ventricular electrogram (ICD sensing electrodes), resulting in oversensing at a sensitivity of 0.15 and 0.3 mV ( Figs. 1 and 2). Corresponding false signals were C

Unrecognized Failure of a Narrow Caliber Defibrillation Lead: The Role of Defibrillation Threshold Testing in Identifying an Unprotected Individual

“…In this case, implant failure would not have been recognized if not for the routine performance of DFT testing. The present report mirrors a previous one of silent lead malfunction, albeit in a standard caliber lead, that was only unveiled on DFT testing 5 . The role of DFT testing at first implant will be clarified by an ongoing multicenter, randomized, controlled clinical trial.…”

“…The present report mirrors a previous one of silent lead malfunction, albeit in a standard caliber lead, that was only unveiled on DFT testing. 5 The role of DFT testing at first implant will be clarified by an ongoing multicenter, randomized, controlled clinical trial. Whatever the outcome, the current case report suggests that DFT testing at generator change may identify the need for lead revision.…”

Is the pace/sense conductor related to a high voltage short circuit in a dual coil ICD system? An experimental study

“…For arc marks to be seen, both the outer and the inner ethylene tetrafluoroethylene (ETFE) insulation layers of the ICD lead must be abraded to bare the metal of the RV coil conductor. In Goldstein's case [2], an inappropriate shock caused by noise was reported, suggesting an HV conductor fracture or failure of the pace–sense conductor [5]. However, the authors did not report any electrical abnormality in the pacing or shock systems, which argue against fracture of the conductors.…”

Defibrillator Threshold Testing at Generator Replacement: Is it Time to Abandon the Practice?

“…From a total of 445 references that were identified through electronic database searches, there were seven case reports [14][15][16][17][18][19][20] and one case series 21 which specifically reported outcomes and complications during DFT testing at ICD generator replacement. The majority of the reports were contemporary, being published from 2012 onwards.…”

“…However, data regarding DFT testing during new ICD implants may not be directly applicable to generator replacement because chronically implanted ICD leads may develop integrity issues over time . Although several reports have cautioned against the abandonment of DFT testing during generator replacement, the issue has been sparingly addressed in the existing literature.…”