Wearable Cardioverter-Defibrillator Benefit Post-ICD Explant
What is the impact of the wearable implantable cardioverter-defibrillator (WCD) in patients who have undergone explantation of an implantable cardioverter-defibrillator (ICD) because of infection?
Data on WCD prescriptions from 2002-2014 were extracted from a national registry maintained by the manufacturer. The wearable device was prescribed to patients who underwent ICD explantation due to infection, and was restricted to those who were not pacemaker dependent. Complete demographic data and other information such as original indication (i.e., primary vs. secondary prevention) were not available.
A total of 8,058 patients (mean age, 62 years; 75% male) received the WCD post-explantation. Among these, 334 patients experienced 406 episodes of ventricular arrhythmias while wearing the device. Among the 406 episodes, 348 (86%) resulted in hemodynamic deterioration. During 54 episodes, patients activated the response button to avert therapy, and the episodes terminated spontaneously. The culprit rhythm was monomorphic ventricular tachycardia (VT) in 40% of the treated episodes, with ventricular fibrillation (VF) accounting for 53%. The median time to first episode of VT/VF after explantation was 29 days. The 2-month and the 1-year cumulative event rates were 4.2% and 10%, respectively. Overall survival rate at 1 year was 66%, and was 76% in patients who were not treated with the WCD. An ICD was re-implanted in 4,505 (80%) patients. Inappropriate shocks were noted in 159 (2%) patients.
Patients who undergo explantation of an ICD because of infection are at risk of VT/VF. The WCD is an effective tool at mitigating risk of sudden death during the period of medical optimization in preparation for potential reimplantation of a permanent device.
Post-extraction patients are at high risk of potentially fatal VT/VF; in fact, as reported in prior studies, at highest risk as compared to patients with other indications for an ICD. The reasons for this heightened risk are not clear, but may be related to serious systemic illness such as endocarditis, which is a frequent indication for explantation. WCD is an effective strategy for reducing this risk during the period of medical optimization. Some patients elect to continue to utilize the WCD, as opposed to undergoing reimplantation of an ICD. Another option for these patients includes the subcutaneous ICD, which is associated with a much lower risk of systemic infection/endocarditis.
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