Wearable defibrillator aids decision making on ICD need

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A management programme that incorporates a wearable cardioverter defibrillator can be used to bridge a decision for appropriate implantable cardioverter defibrillator (ICD) therapy in patients with acquired, inherited and congenital heart disease, according to 18-month results from the WEARIT-II registry presented at Heart Rhythm 2013

“Currently, there is a class I recommendation for implanting ICDs in patients with ejection fraction lower than 35% based on multiple randomised clinical trials. Moreover, there is a general recommendation for primary ICD therapy in high risk patients with inherited arrhythmic disorders,” Ilan Goldenberg, University of Rochester Medical Center, Rochester, USA, told delegates at Heart Rhythm 2013 (8–11 May, Denver, USA). “But we know that not all patients implanted with an ICD receive a survival benefit from the device. For example, in the MADIT II (The multicenter automatic defibrillator implantation trial-II), only one third of patients received appropriate ICD therapy over four years. In MADIT-RIT, ICD programming to

According to Goldenberg, the wearable defibrillator (LifeVest, Zoll) can be used to bridge a decision for appropriate ICD therapy in various populations such as: post-myocardial infarction patients, following coronary revascularisation, new onset dilated (non-ischaemic) cardiomyopathy, high-risk patient until stabilisation, patients with and inherited arrhythmic or congenital disorders. The system includes a response button that can be used to reduce inappropriate therapy with unnecessary shocks.

The WEARIT-II (The prospective registry and follow-up of patients using the LifeVest wearable defibrillator) registry was designed to provide prospective data on the safety and efficacy of the wearable cardioverter defibrillator as a bridging therapy in a real-world setting. All patients prescribed with the device, in the USA, were eligible to take part in the study. The wearing time is two to six months and patients are currently being followed for 12 months. The investigators plan to enrol 2,000 patients in the USA, and currently, the registry is extending to Europe and Israel with additional 1,000 patients planned to enrol. The results presented at Heart Rhythm 2013 were from the first 882 patients enrolled in the USA between August 2011 and April 2013.

The age of patients was 61±12 years, 31% were female and left ventricular ejection fraction was 25±11%; in addition, 29% of patients had diabetes and 28% had atrial fibrillation. The majority of patients (n=771) presented with acquired heart disease. Amongst those, patients with ischaemic cardiomyopathy (n=220) had statistically significant higher rates of diabetes, atrial fibrillation and syncope; non-ischaemic cardiomyopathy patients (n=294) had lower ejection fraction and higher use of ACE-II/ARBs.

The investigators looked at arrhythmic events in the study population with an average wearing of 81±52 days. They found out that there were a total of 70 sustained ventricular tachyarrhythmic events in 21 patients, corresponding to a rate of 36 sustained episodes per 100 patient-years. Events of sustained ventricular tachycardia terminated without wearable defibrillator therapy, withheld by the use of the device response button, occurred in 11 patients (53 events).

When investigators further evaluated the rate of arrhythmic events, they saw that patients with congenital heart disease or inherited arrhythmic disorders had a very high event rate. “In acquired disease patients, we saw that patients with non-ischaemic cardiomyopathy had the lowest rates of arrhythmic events, and patients with ischaemic cardiomyopathy (including early post-myocardial patients) had the highest rates. This can also help us to decide more appropriately if we should implant an ICD latter,” Goldenberg said.

In terms of adverse events, 0.3% of patients received inappropriate therapy, and there were four deaths (0.5), three patients died during hospitalisation (without wearing the defibrillator) and one died while wearing the wearable defibrillator due to asystole. Compliance with the device was relatively good, with a mean of 21±3 hours per day, Goldenberg noted.

He added, “We found out that, following treatment with LifeVest, more than 40% of patients did not receive an ICD because there was improvement in their ejection fraction, thereby possibly preventing a relatively high rate of unnecessary ICD implantations. Furthermore, we have seen that the rate of arrhythmias detected by the LifeVest helped us to make a proper decision regarding the need for ICD therapy, because among patients who received appropriate therapy from the wearable defibrillator while wearing it, more than 80% subsequently got an ICD. In contrast, the rate of ICD implantation following treatment with the LifeVest was lowest among patients who did not experience arrhythmias while wearing the device.”

In conclusion, Goldenberg said, interim results of WEARIT-II showed that a strategy incorporating the wearable defibrillator is safe and effective. “It allows us to appropriately determine the need for permanent ICD implantation, effectively terminate life-threatening arrhythmic events, avoid unnecessary therapies for non-life-threatening arrhythmias and keep a low rate of inappropriate therapies,” he said.

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