Wearable Cardioverter-defibrillator Use Research Articles

Abstract 245: Economic Evaluation of the Wearable Cardioverter-Defibrillator in Patients After ICD Explantation

Introduction Device infection and lead failure are severe complications in implantable cardioverter defibrillator (ICD) recipients. The standard of care includes aggressive antibiotic therapy and in many cases ICD system removal, leaving patients unprotected from sudden cardiac death (SCD). Studies have demonstrated that the wearable cardioverter defibrillator (WCD) is effective in bridging patients while infections are resolved and they can have their devices re-implanted. Hypothesis We sought to evaluate whether WCD is cost-effective in ICD explantation patients. Methods We included all WCD patients whose medical orders indicated an ICD removal. Patients' compliance, shock events, outcomes, and end of use reasons were retrieved from the manufacturer database (ZOLL). Direct and indirect costs other than WCD itself, probabilities of ventricular arrhythmia and mortality were estimated from published articles. The WCD survival rate was calculated as number of saves (remain at home or conscious arrival at the ER) out of the total true shock events. Patients who finished a WCD therapy course were most often re-implanted, with some relying on standard medical therapy only. We used non-WCD patients who utilized the regular emergency medical service (EMS) as the baseline; and computed the incremental cost-effectiveness ratio (ICER) as the difference in costs divided by the difference in lives saved and life-year gained, respectively, within 5 years. Sensitivity analyses were performed to assess how the two ICERs responded as the values of variables changed. All monetary cost was converted to 2010 dollars at a 3% discount rate. Results A total of 3,021 patients used a WCD after an ICD explantation. The mean length of use was 45.4±58.3 days, with an average daily use of 20.35±5.8 hours (85% of the day, median=21 hours). Among those who had ended use, 56.1% got re-implanted. We estimated the first-month mortality was 2.5 times higher than the subsequent months. The calculated ICERs for WCD were $105,869 per life saved and $27,493 per life-year gained. Sensitivity analysis revealed that the ratios were not sensitive to the percentage of re-implantation. Conclusions The use of WCD is highly cost-effective in protecting ICD explantation patients against SCD.

Characteristics and Outcomes of Peripartum Versus Nonperipartum Cardiomyopathy in Women Using a Wearable Cardiac Defibrillator

BackgroundPeripartum cardiomyopathy (PPCM) mortality rates vary between 2% and 56%, with half occurring ≤12 weeks'; postpartum. Although risk factors for PPCM have been identified, predicting sudden cardiac death among PPCM patients remains difficult. This study describes the characteristics and outcomes of PPCM patients and controls referred for a wearable cardioverter defibrillator (WCD). Methods and ResultsDeidentified WCD medical orders between 2003 and 2009 and death index searches were used to characterize women (ages 17–43) with PPCM (n = 107) or matched nonpregnant women with nonischemic dilated cardiomyopathy (NIDCM; n = 159). Demographics were similar. WCD use averaged 124 ± 123 days and 96 ± 83 days among PPCM and NIDCM patients, respectively. No PPCM patients received an appropriate shock for ventricular tachycardia/ventricular fibrillation; 1 NIDCM patient received 2 successful shocks. No PPCM patient died during WCD use versus 11 concurrent NIDCM deaths. After WCD use, 3 PPCM and 13 NIDCM patients died, respectively. ConclusionsThe mortality rate of 2.8% (over 3.0 ± 1.2 years) in PPCM patients is low compared to published data. The role of WCD therapy among PPCM patients deserves further study.

Indications for a Wearable Cardioverter-Defibrillator

The wearable cardioverter-defibrillator (WCD) is an alternative antiarrhythmic device that provides continuous cardiac monitoring and defibrillation capabilities through a noninvasive electrode-based system. Although the WCD has been shown to be highly effective at restoration of sinus rhythm in patients with a ventricular tachyarrhythmia, randomized trials using the WCD in patient populations at elevated risk for arrhythmic death have not been reported. Clinical indications for WCD use are varied and continue to evolve as further experience with this relatively new technology emerges.

Aggregate National Experience With the Wearable Cardioverter-Defibrillator: Event Rates, Compliance, and Survival

The purpose of this study was to determine patient compliance and effectiveness of antiarrhythmic treatment by the wearable cardioverter-defibrillator (WCD). Effectiveness of the WCD for prevention of sudden death is dependent on event type, patient compliance, and appropriate management of ventricular tachycardia/ventricular fibrillation (VT/VF). Compliance and events were recorded in a nationwide registry of post-market release WCDs. Survival, using the Social Security Death Index, was compared with survival in implantable cardioverter-defibrillator (ICD) patients. Of 3,569 patients wearing the WCD (age 59.3+/-14.7 years, duration 52.6+/-69.9 days), daily use was 19.9+/-4.7 h (>90% of the day) in 52% of patients. More days of use correlated with higher daily use (p<0.001). Eighty sustained VT/VF events occurred in 59 patients (1.7%). First-shock success was 76 of 76 (100%) for unconscious VT/VF and 79 of 80 (99%) for all VT/VF. Eight patients died after successful conversion of unconscious VT/VF (89.5% survival of VT/VF events). Asystole occurred in 23 (17 died), pulseless electrical activity in 2, and respiratory arrest in 1 (3 died), representing 24.5% of sudden cardiac arrests. During WCD use, 3,541 of 3,569 patients (99.2%) survived overall. Survival occurred in 72 of 80 (90%) VT/VF events and 78 of 106 (73.6%) for all events. Long-term mortality was not significantly different from first ICD implant patients but highest among patients with traditional ICD indications. Compliance was satisfactory with 90% wear time in >50% of patients and low sudden death mortality during use. Survival was comparable to that of ICD patients. However, asystole was an important cause of mortality in sudden cardiac arrest events.

Studies on the estimation of cardiac output in man, and of abnormalities in cardiac function: Starr, Isaac, Rawson, A. J., Schroeder, H. A., and Joseph, N. R.: Am. J. Physiol. 127: 1, 1939

Cardiac arrest is defined as the termination of cardiac activity associated with loss of consciousness, of spontaneous breathing, and of circulation. Sudden cardiac arrest and sudden cardiac death (SCD) are terms often used interchangeably. Most patients with out-of-hospital cardiac arrest have shown coronary artery disease or symptoms during the hour before the event. Cardiac arrest is potentially reversible by cardiopulmonary resuscitation, defibrillation, cardioversion, cardiac pacing, or treatments targeted at the underlying disease (e.g., acute coronary occlusion). We restrict SCD hereafter to cardiac arrest due to ventricular fibrillation, including rhythms shockable by an automatic external defibrillator (AED), implantable cardioverter-defibrillator (ICD), or wearable cardioverter-defibrillator (WCD). We summarize the state of the art related to defibrillation in treating SCD, including a brief history of the evolution of defibrillation, technical characteristics of modern AEDs, strategies to improve AED access and increase survival, ancillary treatments, and use of ICDs or WCDs.