Wearable defibrillators suitable for children with ventricular arrhythmia

The use of a wearable cardioverter-defibrillator (WCD) may be a suitable alternative for paediatric patients with life-threatening ventricular arrhythmias who are not candidates for implantable cardioverter-defibrillators (ICDs), a recent study showed.

“Our results, which stem from the largest study to date among children in the US using WCDs, suggest that these external devices can help save the lives of children who are at the time, not good candidates for surgically implanted defibrillators because of their medical condition,” said study principal investigator Assistant Professor David Spar from the University of Cincinnati and Cincinnati Children’s Hospital, Cincinnati, Ohio, US.

The study population comprised 455 patients aged <18 years (median age 15 years, 61 percent male) prescribed a WCD between 2009 and 2016, of whom 63 used the WCD because of an ICD problem and 392 who used the WCD for other indications (non-ICD problem). Median duration of WCD use was 33 days at a median of 20.6 hours/day. The system was programmed to deliver a median shock of 150 J.

The ICD-related problems for which the WCD was prescribed were mostly mechanical issues such as lead fracture or lead extraction (57 percent) or infection (38 percent), while non-ICD problems were mostly related to cardiomyopathy (43 percent), congenital heart disease (23 percent), or channelopathies (12 percent). Sixty percent of patients in the non-ICD problem group had either cardiac arrest, a history of ventricular arrhythmia, or concern regarding arrhythmogenic syncope prior to WCD placement.

Patients with ICD-related problems used the WCD for a shorter period compared with patients with non-ICD problems (26 vs 35 days; p<0.05). [Circ Arrhythm Electrophysiol 2018;11:e006163]

WCD shock treatment was discharged for eight patients, one and seven in the ICD-problem and non-ICD problem groups, respectively. Of these, six patients received a total of 13 treatments for seven episodes of polymorphic ventricular tachycardia or ventricular fibrillation, all of which were successfully treated with a 100 percent survival rate. Two patients received “inappropriate therapy”, which was defined in this study as therapies for any non-ventricular tachycardia or ventricular fibrillation rhythm, which was dispensed for “oversensing of artifact during asystole” and “noise/artifact during sinus rhythm” (n=1 each).

The most frequent reasons for WCD removal were for ICD repair or placement (44 percent), improvement of ejection fraction (15 percent), or a heart transplant or placement of ventricular assist device (4 percent), though 32 percent had the WCD removed for a non-medical reason.

None of the patients who died (n=7) were wearing the WCD at time of death. According to the researchers, the patients who died may have been “sicker” than the rest of the study population as four patients were on milrinone and four hospitalized at time of death.

“ICDs are known to have relatively high rates of complications in the paediatric population, most commonly lead-related problems, and have a significant effect on the patient’s quality of life. For these reasons using a WCD instead of an ICD may be favourable in certain circumstances, particularly if the patient’s condition may improve,” said the researchers.

“The combination of low rates of inappropriate therapy and only a small percentage of patients that personally aborted therapy [6 percent] are likely important for patient compliance and their quality of life,” they said.

“Paediatric patients overall had adequate compliance with WCD use [and] the WCD is safe and effective in treating ventricular arrhythmias that can lead to sudden cardiac death in paediatric patients,” the researchers added, cautioning that the device may not be suitable for patients who are at high risk of developing asystolic cardiac arrest.