Programming of Implantable Cardioverter-Defibrillators on the Basis of the Upper Limit of Vulnerability

Author:

Swerdlow Charles D.1,Peter C. Thomas1,Kass Robert M.1,Gang Eli S.1,Mandel William J.1,Hwang Chun1,Martin David J.1,Chen Peng-Sheng1

Affiliation:

1. From the Division of Cardiology (C.D.S., C.T.P., E.S.G., W.J.M., C.H., D.J.M., P.-S.C.) and the Department of Cardiovascular Surgery (R.M.K.), Cedars-Sinai Medical Center, Los Angeles, Calif.

Abstract

BackgroundA patient-specific measure of defibrillation efficacy that requires a minimum number of ventricular fibrillation (VF) episodes would be valuable for programming implantable cardioverter-defibrillators (ICDs). The upper limit of vulnerability (ULV) is the weakest shock strength at or above which VF is not induced when a stimulus is delivered during the vulnerable phase of the cardiac cycle. It correlates with the defibrillation threshold (DFT) and can be determined with a single episode of VF. The objective of this study was to test the hypothesis that ICDs programmed on the basis of the ULV convert spontaneous ICD-detected VF reliably.Methods and ResultsWe studied 100 consecutive patients at ICD implantation and during follow-up of 20±7 months. At implantation, the ULV and DFT were determined, and the ICD system was tested at a shock strength equal to the ULV+3 J. During follow-up, the strength of the first shock was programmed to the ULV+5 J for arrhythmias detected in the VF zone (cycle length <292±17 ms). We reviewed stored detection intervals and electrograms from spontaneous episodes of ICD-detected VF to determine the success rate for appropriate first shocks. The programmed first-shock strength was 17.5±5.2 J. During follow-up, there were 120 appropriate first shocks in 37 patients. The arrhythmia was rapid monomorphic ventricular tachycardia (VT) in 70% of episodes (31 patients), VF in 11% (13 patients), polymorphic VT in 1%, and unclassified in 17% (15 patients). The first shock was successful in 119 of 120 episodes (99%; 95% CI, 93% to 100%). One unclassified episode required two shocks. No patient had syncope associated with an ICD shock or arrhythmic death.ConclusionsICD shocks can be programmed on the basis of the ULV, a measurement made in regular rhythm, without a direct measure of defibrillation efficacy.

Publisher

Ovid Technologies (Wolters Kluwer Health)

Subject

Physiology (medical),Cardiology and Cardiovascular Medicine

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