Abstract of presentation made by Dr. Sven Reek at the National Association of Pacing and Electrophysiology Conference on May 10, 2002, in San Diego, California
Clinical Efficacy of the Wearable Defibrillator in Acutely Terminating Episodes of Ventricular Fibrillation Using Biphasic Shocks
Sven Reek, MD, Ulf Meltendorf, MD, Anke Wollbrueck, Steven J. Szymkiewicz, MD*, Helmut U. Klein, MD and J. Christoph Geller, MD. Univ. Hospital Magdeburg, Magdeburg, Germany and Lifecor, Germany.
The wearable defibrillator (WCD, LIFECOR, Inc.) automatically detects and treats ventricular tachyarrhythmias by delivering direct current shocks. The current device generation uses a monophasic truncated exponential waveform with a maximum energy output of 285 Joules. The purpose of this study was to test the clinical efficacy of a new biphasic shock waveform for acute termination of induced ventricular fibrillation (VF).
The WCD consists of a chest garment with installed ECG and shocking electrodes and an alarm and monitoring patient interface unit. The device is designed to detect and treat ventricular tachyarrhythmias automatically. The new WCD generation delivers a biphasic truncated exponential shock with a maximum programmable energy output of 150 Joules. Ten patients (2 female, age 61 +/ 11 years, weight 84+/ 8 kg, left ventricular ejection fraction 30+/ 9 %) with a history of ventricular tachyarrhythmias underwent an electrophysiological study. Two episodes of VF were induced in all patients.
Termination of electrically induced VF was attempted using the WCD. For this study capacitor charging and shock delivery were performed manually by one of the operators. All patients received one 70 Joules and one 100 Joules shock in a randomized order. Shocks were delivered manually 22 +/ 6 sec (70 Joules) and 21 +/ 6 sec (100 Joules) (P =NS) after arrhythmia initiation. All 20 VF episodes were terminated successfully by 70 Joules or 100 Joules shocks. The findings of our initial study demonstrate the ability to terminate induced VF reliably (100% of all episodes) by a single low energy biphasic shock delivered by the WCD. These results suggest an acceptable safety margin to the maximum energy output of the device for the use under clinical conditions.