Clinical Efficacy of a Wearable Defibrillator in Acutely Terminating Episodes of Ventricular Fibrillation Using Biphasic Shocks

Abstract

The Wearable Cardioverter Defibrillator (WCD) automatically detects and treats ventricular tachyarrhythmias without the need for assistance from a bystander, while at the same time allowing the patient to ambulate freely. It represents an alternative to emergency medical services for outpatient populations with a temporary risk of sudden cardiac death. While the original devices used a monophasic truncated exponential waveform for cardioversion/defibrillation shocks, a new, biphasic shock was developed for the next device generation. In 12 patients undergoing electrophysiological testing for ventricular tachyarrhythmias, termination of electrically induced ventricular fibrillation (VF) was attempted via the WCD. In 22 episodes, induced VF was promptly terminated by the first 70 J (n=12) or 100 J (n=10) biphasic shocks. Time between arrhythmia initiation and shock delivery was 22 +/- 6 seconds (70 J) and 21 +/- 6 seconds (100 J) (P=NS). The measured transthoracic impedance was 71 +/- 5 Ohms (64-79 Ohms) for the 70 J shock and 64 +/- 8 Ohms (47-72 Ohms) for the 100 J shock. The present study demonstrates that a single low energy biphasic shock delivered by the WCD, reliably terminates electrically induced VF (100% of episodes). The results of this study suggest that there is an acceptable safety margin to the maximum output of the device (150 J). Despite our promising data, we recommend that programming all shocks for maximum energy output should be done when using the WCD in ambulatory patients.

Wearable Cardioverter-Defibrillator Therapy for the Prevention of Sudden Cardiac Death

“…45 WCD shock energies range between 75 and 150 J biphasic, and shock efficacy rates between 69% and 99% have been reported. 42,[46][47][48] WCD devices are capable of delivering up to 5 shocks; however, once the device has treated an episode of arrhythmia, the garment and electrodes must be replaced. Although the vast majority of observational data are from adults, small series have reported WCD use in pediatric populations, including patients 9 to 17 years of age.…”

Der tragbare Kardioverter-Defibrillator

“…Die Wirksamkeit, also die Fähigkeit des WCD, ventrikuläre Tachykardien und Kammerflimmern sicher zu terminieren, ist durch verschiedene Arbeiten belegt [8][9][10]. Während oft moniert wird, dass deutsche Medizintechnologien lediglich legitimiert durch ein CE-Kennzeichen den Weg zum Patienten finden, wurde die LifeVest® bereits 2001 aufgrund der kombinierten WEA-RIT/BIROAD-Daten von der US-amerikanischen Arzneimittelbehörde FDA zugelassen [10].…”

Wearable Cardioverter-Defibrillators

“…In the first 2 small-scale clinical trials evaluating the efficacy of the wearable defibrillator in terminating rapid VT and VF episodes induced by programmed ventricular stimulation in the catheterization laboratory (the Table), all ventricular arrhythmic events (31 events in 21 patients) were successfully terminated. 3,4 In contrast to ICD trials, no attempt was made to define the defibrillation threshold in these trials. Instead, the wearable defibrillator was programmed to deliver a shock with the same prespecified energy to all patients (230-J monophasic 5 These 2 trials, united into 1 trial at the request of the FDA, included a total of 289 patients either with advanced heart failure and a left ventricular ejection fraction (LVEF) <30% or at high arrhythmic risk after a myocardial infarction (MI) or recent coronary artery bypass grafting (the Table).…”