Defibrillation Testing Should the Paradigm Shift?⁎

In 3 decades of clinical use of the implantable cardioverter-defibrillator (ICD),defibrillation threshold (DFT) testing has remained an integral part of the implantation procedure. The prevailing rationale for the routine evaluation of DFTs has been to ensure appropriate sensing of ventricular fibrillation,system integrity,and effective defibrillation (1–3). Early ICD systems using monophasic waveforms with epicardial patches or transvenous leads were associated with a substantial incidence of elevated DFTs,requiring additional intervention to ensure clinical efficacy (1–3). Technically,the DFT is a probabilistic phenomenon requiring multiple shocks to determine with precision. Clinically,the DFT is commonly approximated with 1 or more shocks to terminate induced ventricular fibrillation and ensure a safety margin between the DFT and the maximum output of the ICD. Inadequate safety margins of <10 J between the DFT and maximum ICD energy delivery have been associated with worse clinical outcomes (3). Contemporary ICD systems using active cans,pectoralis pulse generators,biphasic waveforms,and intravascular high-voltage leads have considerably lowered the incidence of elevated DFTs (4–13). The reliability of current ICD systems has led implanting physicians to abandon the practice of routine testing of defibrillation efficacy before hospital discharge and annually. Observational studies also have noted an elimination of DFT testing in one-third of initial implants and two-thirds of replacements (14–16). Indeed,based on a growing body of evidence,the clinical utility of the determination of defibrillation efficacy during de novo implants has been questioned (4–13). With this background,it is appropriate to re-evaluate whether DFT testing still should be routinely performed at the initial ICD insertion procedure.
Journal of the American College of Cardiology Current Issue

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