Europace Advance Access originally published online on October 3, 2007
Europace 2007 9(12):1161-1162; doi:10.1093/europace/eum182
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ICDS
Non-determinable defibrillation threshold and inefficacy of implantable cardioverter/defibrillator shocks due to defective connections of the defibrillator lead terminals in the device header port
Department of Cardiology and Angiology, Medizinische Klinik II, Ruhr-University Bochum, Hölkeskampring 40, 44625 Herne, Germany
Manuscript submitted 4 May 2007. Accepted after revision 20 July 2007.
* Corresponding author. Tel: +49 2323 499 1600; fax: +49 2323 499 301. E-mail address: petra.maagh{at}ruhr-uni-bochum.de
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Abstract |
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 Top Abstract IntroductionCase reportDiscussion |
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Inefficacy of implantable cardioverter/defibrillator (ICD) shocks or inappropriate shocks in ICD patients may occur due to mechanical or technical failure of the device. In our unusual case of ICD defibrillation failure, faulty insertion and configuration of the defibrillation lead in the header port resulted in ineffective shock therapies and a non-determinable defibrillation threshold. In cases of successless defibrillations during or after ICD implantation, this problem should be considered.
Key Words: Cardioverter/defibrillator (ICD), Defibrillation threshold, ICD defibrillation failure, Ineffective shock therapies
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Introduction |
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TopAbstractIntroductionCase reportDiscussion |
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Correct system function of implantable cardioverter/defibrillator (ICD) devices requires reliable operation of electronic and mechanical components. Diagnostic functions are often insufficient in diagnosing mechanical failures. We present an ICD patient in whom an unusual source of ineffective ICD therapies resulting in ICD malfunction was identified.
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Case report |
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TopAbstractIntroductionCase reportDiscussion |
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An 83-year-old man with several syncopal episodes due to idiopathic sustained ventricular tachycardias (VT), also on amiodarone, received a Guidant Vitality® (CPI model VITALITY 2 ICD T 175 VR, Guidant, Belgium) ICD with integrated bipolar lead (dual coil, model number 0176). At implant pacing, threshold was 0.8 V/0.5 ms, RV lead impedance 900
, high voltage impedance 40 , and R-wave sensing 10.5 mV. Minimal shock energies required for successful defibrillation were 11 J. Ventricular fibrillation (VF) was induced twice; all VF episodes were correctly identified without dropouts. The initial postprocedural course was unremarkable. Subsequent device follow-up were spaced once at 6 weeks after implantation, later at intervals of 3 months. After 1 year, amiodarone was terminated due to side effects. VT occurred with consecutive ICD shocks. Sotalol, mexiletin, propafenon, and flecainid were ineffective.
Two years after implantation, an electrical storm occured (Figure 1). Device interrogation showed normal battery voltage, lead impedances, sensing, and pacing threshold but several ineffective ICD discharges. The device was programmed as follows: (i) VT detection > 190 b.p.m., therapies = ATP x 3, 21 J x 1, 31 J x 3 and (ii) VF detection >210 b.p.m., therapies = 21 J x 1, 31 J x 5. VF was induced but the ICD failed to terminate the arrhythmia.
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270 ms), initially treated with a 21 J shock, accelerated. VF was treated twice with 31 J shocks, but ineffective. The fourth 31 J shock terminates VF.The patient was referred for reimplantation of a high-energy device. We found the lead terminals in the header physically reversed. The shocking lead terminal labelled ‘distal’ was inserted into the positive (+) lead port and the shocking lead terminal labelled ‘proximal’ was inserted into the negative (–) one. This resulted in the highest current density occurring over the right atrium (RA) instead of in the ventricle where it is required for effective defibrillation.
After changing insertion of lead terminals in the header, ICD showed correct function during follow-up. Shock therapies terminated VT and VF effectively.
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Discussion |
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TopAbstractIntroductionCase reportDiscussion |
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The most reported ICD malfunctions are related to structural failure of the leads (e.g. endocardial lead migration, insulation break) or defibrillation-related problems (e.g. increase of DFT, excessive charge time). To the best of our knowledge, a comparable case like ours of ‘ICD malfunction’ has not been reported. It is due to the fact of a technical mistake of physically reversing the leads in the header that not only the shock current pathway but also the sensing configuration were suboptimal. Because of such error, apart from non-conversion of arrhythmias, a broad, unipolar sensing configuration between lead tip and device occured. Sensing of pectoralis muscle activity may have resulted in oversensing and/or delivery of inappropriate therapies.
Similar problems can occur with all integrated bipolar leads of all manufactures if they have a physical connection between the IS-1 terminal ring and distal coil.
This case stresses the need to be vigilant of such simple problem in cases of failed defibrillation.
Conflict of interest: none declared.
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