The time is not ripe for the wearable cardioverter-defibrillator

This editorial refers to ‘Extended use of the wearable cardioverter-defibrillator in patients at risk for sudden cardiac death’ by V. Kutyifa et al., pp. f225--f232.

In this issue of EP-Europace, Kutyifa et al.¹ present data from the North American WEARIT-II registry, comparing the incidence of tachyarrhythmia between patients with extended use of the wearable cardioverter-defibrillator (WCD) beyond 90 days and patients with shorter use. The results of the WEARIT-II registry, published in 2015, included 2000 consecutive patients with newly diagnosed heart failure and implantable cardioverter-defibrillator (ICD) naive treated with WCD during the years 2011–14.² In the most recent article, including the cohort from the original report, rates of ventricular arrhythmia, treated and untreated, were lower in the extended use group.¹ Number of patients with WCD-treated ventricular arrhythmia was 3 out of 981 within a median period of 120 days in the extended use group, and low despite the aetiology of heart failure. Of significant interest, implantation of ICD was not performed in one-third of patients with extended WCD use because left ventricular ejection fraction (LVEF) had improved during WCD carriage to a level where ICD was no longer indicated. How should we use these data and other observational reports when deciding whether or not to use WCD in our patients?

Current European Society of Cardiology (ESC) 2015 guidelines on prevention of sudden cardiac death recommend that WCD use may be considered (Class IIb, level of evidence C) for adult patients with poor left ventricular systolic function who are at risk of sudden arrhythmic death for a limited period, but are not candidates for an ICD, and for selected patients <40 days after myocardial infarction, as those with incomplete revascularization, pre-existing left ventricular dysfunction, occurrence of arrhythmias >48 h after the onset of acute coronary syndrome, or with polymorphic ventricular tachycardia or fibrillation.³ The recommendations for heart failure patients are repeated in the 2016 ESC guidelines on treatment of heart failure. However, these guidelines also point out the lack of randomized trials on the use of WCD early after diagnosis of heart failure.⁴

The incidence of ventricular arrhythmia reported in this article¹ may motivate physicians to consider WCD use in more patients in the early period after diagnosing of heart failure. However, before implementing that, several caveats need to be kept in mind. These data on WCD use are observational, and there is no control group for comparison. It is not clear, how many patients declined to participate in the registry and how representative the population included is, nor is the reason for the chosen length of observation period. The endpoints reported were sustained and non-sustained ventricular arrhythmia, of which only a minority needed treatment from the WCD. It is well acknowledged that an episode of ventricular arrhythmia treated by an ICD or a WCD cannot be counted as a saved life. Likely, most arrhythmia episodes had not caused death or cardiac arrest. Therefore, whether the WCD did in fact have any benefit in this group of patients cannot be judged from data of this character.

Luckily, we now have the primary results of the first large scale randomized controlled trial of WCD early after myocardial infarction. The multicentre Vest Prevention of Early Sudden Death Trial (VEST) was reported as a late-breaking clinical trial at the 2018 meeting of the American College of Cardiology (http://www.acc.org/latest-in-cardiology/clinical-trials/2018/03/09/08/06/vest) while the details are still awaited in a publication. The VEST trial aimed to investigate whether a WCD reduces sudden death mortality in the immediate post myocardial infarction period (<90 days) in patients with reduced LVEF, as a bridge to evaluation for ICD. A total of 2302 patients with LVEF ≤35% were included within 7 days of hospital discharge for acute myocardial infarction, randomized to WCD plus guideline-recommended treatment (n = 1524) or guideline-recommended treatment with no WCD (n = 778). After mean follow-up of 84 days, the incidence of the primary outcome event, sudden death or death due to ventricular tachyarrhythmia, did not differ between the two treatment groups. A total of 20 patients had received appropriate WCD shock therapy during their follow-up, and 10 patients experienced inappropriate shock therapy. The secondary endpoint of all-cause death occurred significantly less frequent in the WCD group (3.1% vs. 4.9%, P = 0.04). It is difficult, however, to understand any positive WCD effect beyond protecting from death because of ventricular tachyarrhythmia, and the main message from the VEST trial is that of the neutral outcome with respect to the primary outcome event.⁵ These results are very much in line with the results of the older randomized controlled trials investigating the effect of ICD implantation early after myocardial infarction,^6,7 and the current recommendations in the ESC 2015 guidelines for prevention of sudden cardiac death.³

Furthermore, cost-effectiveness of the WCD still is not sufficiently known. For patients undergoing removal of an infected ICD, discharge with WCD was found cost-effective in a North American setting assuming a quite high 5.6% 2 month risk of sudden cardiac arrest and at least 2 weeks of time to re-implantation.⁸ Implementation of WCD use early after diagnosis of heart failure may have major impact on health care resources. This need to be considered from an economical perspective as reimbursement of device treatment and subsequent device implantation is highly variable throughout Europe.⁹ Cost-effectiveness evaluation in this scenario, therefore, is highly relevant along with randomized controlled trials on the potential clinical benefit of the WCD.

In one-third of the patients with extended WCD use, an ICD was no longer indicated at end of WCD use because of improved left ventricular function, and the authors suggest that ‘WCD use >90 days could potentially improve risk stratification for an ICD in ischaemic and non-ischaemic cardiomyopathy patients’.¹ How to improve risk stratification with the WCD must await prospective, controlled data, and cannot build upon results from analysis of registry data. Still, LVEF is the most commonly used single prognostic factor when deciding on ICD use. Not because it is a very good prognostic factor, rather because it is the least bad we currently have.

Use of the WCD in newly diagnosed heart failure has to await the conduct of well-designed and sufficiently powered randomized controlled trials showing a benefit from this device.

Funding

This work was supported by the Novo Nordisk Foundation [NNF16O0018658 and NNF17OC0029148 to J.C.N.].

Conflict of interest: J.C.N. has received an institutional research grant from Abbott, Denmark. J.B.J. has no conflicts to declare.

The opinions expressed in this article are not necessarily those of the Editors of Europace or of the European Society of Cardiology.

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