Conference Coverage

Wearable defibrillator vest useful as bridge to ICD


 

AT HEART RHYTHM 2013

DENVER – The LifeVest wearable automatic defibrillator provides a safe and highly effective bridging strategy while physicians decide whether a patient should get an implantable cardioverter defibrillator, according to findings from the WEARIT-II registry.

Experience gleaned from the first 882 of a planned 3,000 patients to be enrolled in this prospective, real-world registry indicates the defibrillator vest consistently recognizes and safely terminates life-threatening arrhythmias while avoiding unnecessary shocks for non–life-threatening arrhythmic events, Dr. Ilan Goldenberg reported at the annual meeting of the Heart Rhythm Society.

Dr. Ilan Goldenberg

Indeed, the inappropriate shock rate in WEARIT-II was a mere 0.3%, far lower than with contemporary implantable cardioverter defibrillator (ICD) therapy, noted Dr. Goldenberg of the University of Rochester (N.Y.).

This bridging strategy deserves broad use in high-risk populations, he said. The WEARIT-II data show that bridging is particularly useful as a means of protecting patients with a transient arrhythmia risk as well as those whose long-term arrhythmia risk is undefined and requires further evaluation. Examples include patients who are post MI, or have new-onset heart failure with a depressed left ventricular ejection fraction (LVEF) of 35% or less, have recently undergone coronary revascularization, or are undergoing detailed evaluation of a possible inherited or congenital arrhythmic disorder.

Guidelines state that an ICD is indicated for primary prevention of sudden cardiac death in patients with an LVEF of 35% or less, but not within 40 days following an MI, or within 3 months after diagnosis of heart failure, or within 90 days following coronary revascularization. The reason for these mandatory delays is that many patients will experience improvement in LVEF in response to medical therapy such that they no longer qualify for ICD implantation. But if their physician is concerned about their arrhythmia risk during that waiting period, the wearable defibrillator is an excellent solution, Dr. Goldenberg continued.

There is a clear need for more selective prescription of ICDs for primary prevention of cardiac arrest. This was already evident more than a decade ago, when the MADIT-II (Multicenter Automatic Defibrillator Trial–II) demonstrated that only one-third of patients received appropriate ICD therapy during 4 years of follow-up (N. Engl. J. Med. 2002;346:877-83). More recently, the MADIT-Reduce Inappropriate Therapy trial reported that participating ICD recipients had a low appropriate shock rate of 3 shocks per 100 patient-years (N. Engl. J. Med. 2012;367:2275-83) . The wearable defibrillator bridging strategy offers a means of safely being more selective in ICD placement. Patients whose risk isn’t yet clearly defined can in effect have a nonpermanent trial run of up to 6 months’ duration using the LifeVest, the electrophysiologist explained.

The LifeVest is commercially available and routinely covered by insurers. It’s a thin, lightweight vest designed to be worn under clothes. It is attached to a waist battery pack. The LifeVest provides continuous heart rhythm monitoring and automatic defibrillation upon detection of a potentially fatal ventricular arrhythmia. The device has an override button that enables a patient experiencing a sustained ventricular tachyarrhythmia (VT) to allow the event to terminate spontaneously, thereby avoiding unnecessary shocks. Should the patient pass out while the VT continues, the LifeVest will deliver shock therapy.

The 882 patients in the WEAR-IT registry had a mean LVEF of 25%. A total of 771 patients had acquired heart conditions, most commonly nonischemic or ischemic cardiomyopathy. The other 111 patients had inherited or congenital conditions, such as long QT syndrome. Patients wore the LifeVest for an average of 81 days and for a mean of 21 hours daily.

Appropriate LifeVest shock therapy that terminated life-threatening fast VT or ventricular fibrillation occurred at a rate of 9 events per 100 patient-years. Sustained VT that was allowed to spontaneously terminate as a result of the patient’s use of the device’s override button occurred at a rate of 27 events per 100 patient-years.

The device also detected nonsustained VT at a rate of 47 events per 100 patient-years, atrial arrhythmias and other supraventricular tachycardias at 64 events per 100 patient-years, and asystole at 3 events per 100 patient-years.

Four deaths occurred. Three of those happened when the patient was not wearing the vest; the fourth was caused by asystole.

Upon ending their use of the LifeVest, 41% of patients did not receive an ICD because their LVEF improved. Moreover, the arrhythmias detected by the LifeVest affected patient disposition: 80% of patients who received an appropriate shock from the vest got an ICD, as did fewer than 40% of those with no arrhythmias detected during vest wear.

Patients within 40 days post MI or 90 days post revascularization had the highest arrhythmic event rates among those with acquired heart conditions; however, the event rate was even higher among those with inherited or congenital conditions.

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