Using Wearable Cardioverter Defibrillators After Explantation of ICDs

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After explantation, the median time to a first VT/VF event was 29 days.
After explantation, the median time to a first VT/VF event was 29 days.

Wearable cardioverter defibrillators may be an effective alternative to implantable cardioverter defibrillators (ICDs) in patients at high risk of ventricular tachycardia and ventricular fibrillation (VT/VF) when re-implantation is delayed, according to research published in JACC: Clinical Electrophysiology.

Kenneth A. Ellenbogen, MD, FACC, chairman of the division of cardiology at Virginia Commonwealth University in Richmond, and colleagues conducted this retrospective study to determine the risk of VT/VF after ICD explantation and to define that risk trend over time. 

“Lead-associated endocarditis is the most common indication for [an] ICD explant,” the authors wrote. “Unlike lead fracture or ICD mechanical malfunction, device-related infection often requires delayed re-implantation after complete ICD system removal due to prolonged antibiotic therapy.”  

Dr Ellenbogen and colleagues collected data from a wearable cardioverter defibrillator manufacturer-maintained US registry. A total of 8058 patients (mean age: 62 years; 75% male) were included in the study; 334 patients experienced 406 VT/VF events, with the majority of patients only experiencing 1 event.   

Of the 406 VT/VF events, 348 were considered “hemodynamically unstable” (ie, the patient lost consciousness and did not use the response buttons during the event) and resulted in shocks by the wearable cardioverter defibrillator. However, in 54 of the VT/VF events, patients did not lose consciousness and were able to use the response buttons to delay the shocks. Their arrhythmias ended without intervention.

After an ICD was explanted, the median time to a first VT/VF event was 29 days, more commonly occurring early after the explantation. The weekly event rate was 0.9% (95% confidence interval [CI], 0.7%-1.1%) during the first week, 0.7% (95% CI, 0.5%-0.9%) during the second week, and 0.7% (95% CI, 0.6%-1.0%) the following week. From the fourth week through the end of the second month, the event rate slightly decreased to 0.4% (95% CI, 0.3%-0.7%), with the exception of the fifth week (0.6%; 95% CI, 0.5%-0.9%).

While the VT/VF event incidence decreased over time, the risk remained throughout the duration of follow-up, with a cumulative 1-year VT/VF rate of 10% (95% CI, 9%-12%).

After ICD explantation, nearly 80% of patients continued to use the wearable cardioverter defibrillator for up to 3 months, which suggests that the device can be worn safely for prolonged periods of time.

“Better characterization of patients receiving a WCD [wearable cardioverter defibrillator] will be useful to further risk stratify benefit and risk of sudden cardiac death,” the researchers concluded.

Study Limitations

This study was retrospective in nature, relying on data from the manufacturer's registry and as such comprehensive information was unavailable for most patients. In addition, a long-term survival benefits analysis was impossible to conduct based on the data collected here. The researchers noted a prospective study may be necessary.

Disclosures: Drs Wan and Szymkiewicz are employees of Zoll Medical Corporation.

Reference

Ellenbogen KA, Koneru JN, Sharma PS, et al. Benefit of the wearable cardioverter defibrillator in protecting patients after ICD explants: results from the national registry. JACC Clin Electrophysiol. 2016 Nov. doi:10.1016/j.jacep.2016.09.002 [Epub ahead of print].

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