Inappropriate defibrillator shocks from depolarization - Repolarization mismatch in a patient with hypertrophy cardiomyopathy

Suraj Kapa, Jay H. Curwin, Robert F. Coyne, Stephen L. Winters

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Despite wide use of dedicated bipolar sensing electrodes in implantable cardioverter-defibrillator (ICD) systems, oversensing occasionally occurs, leading to unwarranted shocks or antitachycardia pacing. This case report highlights an individual with hypertrophic cardiomyopathy (HCM) who experienced inappropriate shocks from oversensing of repolarization electrograms (T-waves). During the implantation procedure, no excessive T-wave amplitudes were detected during sinus rhythm, ventricular pacing, or induced ventricular fibrillation. T-wave oversensing leading to shocks only developed after maturation of the lead-tissue interface. An adequate safety margin for discrimination between ventricular electrograms and T-waves could not be assured. Thus, insertion of a new dedicated pacing-sensing electrode was required. The degree to which intracardiac repolarization signals may be heightened in patients with HCM has not been investigated systematically. However, a relative decrease in the ventricular electrogram amplitude without a concomitant decline of the intracardiac T-wave amplitude appears to have led to the problem in this patient. Special caution in technique and device selection with a particular emphasis on T-wave sensing may be prudent when ICDs are implanted in individuals with HCM. Additional programmable variables may also be beneficial in such cases.

Original languageEnglish (US)
Pages (from-to)1408-1411
Number of pages4
JournalPACE - Pacing and Clinical Electrophysiology
Issue number11
StatePublished - Nov 2007

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine


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