The implantable cardioverter-defibrillator has firmly established itself as a treatment option for patients at high risk for life-threatening ventricular tachyarrhythmias. In fact, several large randomized-controlled studies have supported its efficacy in preventing sudden cardiac death (SCD) and in reduction of mortality in patients with ischemic cardiomyopathy (ICM) and an ejection fraction (EF) ≤35% at least 6 weeks after the ischemic event or nonischemic cardiomyopathy (NICM) and an EF ≤35% after at least 3 months of optimal medical therapy (OMT) in primary prophylaxis [
The wearable cardioverter-defibrillator is a noninvasive device used temporarily for the prevention of SCD in presumed high-risk patients, which do not meet ICD implantation criteria on the basis of current guidelines. So far, only one wearable cardioverter-defibrillator (WCD) is approved for clinical use (LifeVest, ZOLL, Pittsburgh, Pennsylvania, USA). The device is a wearable vest with built-in electrodes for rhythm sensing, and pads in case a shock must be delivered [
Ventricular flutter and fibrillation detected and appropriately terminated by a WCD in a patient.
The aim of this study was to provide a systematic analysis of the published data on WCD-recorded appropriate shocks in different patient cohorts for extended time periods. The focus of our investigation was device wear length and time to the first appropriate shock. Our goal was to provide an overview of current data on prolonged WCD use in available literature and point out specific populations which seem to benefit most from it.
Studies were identified searching PubMed from the start of the database until the end of 2017 using the term “wearable cardioverter defibrillator” or “wearable cardioverter-defibrillator” and “wcd.” Only English-written articles were considered. Abstracts of all search results were screened and only original clinical studies, excluding case reports and small case series with
The PubMed search resulted in a total of 127 publications. 101 were either not clinical studies or did not report on WCD use. The remaining 26 articles were screened, and 15 publications met the inclusion criteria. One study was excluded because of conflicting numbers reported in the dataset (the authors could not be reached for clarification) [
Study selection flow chart. WCD = wearable cardioverter-defibrillator.
The investigated 14 clinical studies were published between 2010 and 2017 (Table
Studies reviewed.
Year | Author | Indication |
|
Median wear time | Maximal wear time | Number of appropriate shocks | Median time to the first appropriate shock | Maximal time to the first appropriate shock |
---|---|---|---|---|---|---|---|---|
2010 | Collins et al. [ |
Any (≤18 years of age) | 81 | 29 | 531 | 0 | No shocks | No shocks |
Any (18–21 years of age) | 103 | 35 | 499 | 5 |
|
| ||
2010 | Chung et al. [ |
Any | 3569 | 36 | 1590 | 80 |
|
|
2010 | Klein et al. [ |
Any | 354 | 106a | >7 years | 21 |
|
|
2010 | Dillon et al. [ |
Any | 2105 | 36 | 365 | 54 |
|
|
2012 | Kao et al. [ |
Heart failureb | 82 | 64 | 277 | 0 | No shocks | No shocks |
2013 | Epstein et al. [ |
ICM | 8453 | 57 |
|
309 | 9 | >9 months |
2014 | Wan et al. [ |
Hemodialysed patientsc | 75 | 62.9a | 308 | 136 |
|
|
2014 | Tanawuttiwat et al. [ |
Device infection | 97 | 21d |
|
4 | 23 | 38 |
2015 | Singh et al. [ |
ICM | 271 | 53 |
|
6 | 34 | 45 |
NICM | 254 | 71 |
|
0 | No shocks | No shocks | ||
2016 | Lamichhane et al. [ |
HFrEFe | 220 | 394 | 2013 | 13 |
|
|
2016 | Wäßnig et al. [ |
Any | 6043 | 59 | 163 |
|
|
|
2017 | Erath et al. [ |
Any | 1102 | 54 | 166 | 8 |
|
|
2017 | Sasaki et al. [ |
Any | 50 | 16 | 171 | 6 | 12 | 30 |
2017 | Duncker et al. [ |
PPCM | 49 | 120a |
|
5 | 68 | 124g |
aReported as a mean; bdefined by own specific criteria; conly patients with SCD events included; dmedian calculated for only 80 study patients; ewear time always >90 days; f89% of treatments occurred in the first 90 days; gcalculated from the time of diagnosis and not from the beginning of device therapy;
The size of study populations ranged from 49 to 8453 patients in the investigated studies, and a total of 22908 patients were primarily reviewed for this analysis. All studies reported the median wear time (in 3 studies mean wear time [
The prevalence of prolonged use was not specifically reported in either of the studies, except for the study of Lamichhane et al. which specifically only included long-term WCD users [
Shortest and longest device parameters reported in the included studies.
Median wear time | Maximal wear time | Median time to the first appropriate shock | Maximal time to the first appropriate shock | |
---|---|---|---|---|
Shortest | 16 | 163 | 9 | 30 |
Longest | 394 | >7 years | 68 | >9 months |
The number of appropriate shocks per total study population varied greatly among the different indications. The highest rate observed was in patients on hemodialysis (136 appropriate shocks in 75 patients) [
We here provide the first systematic review of published data on prolonged WCD use in clinical practice and patients most likely to benefit from it.
From the published data, it is evident that prolonged use of WCD was rarely reported in patients with ICM and ejection fraction ≤35%. This is not surprising, considering current guidelines giving an IA indication for ICD implantation 3 months after an MI or PCI/CABG with persistent symptomatic systolic heart failure based on the SCD-HeFT and MADIT-II trials [
Singh et al. however report that only half of all shocks were in the first 40 days after an index MI suggesting that several cases of malignant arrhythmia occur after the initial waiting period. This difference to Epstein’s results cannot clearly be explained, since EF and medication (including antiarrhythmic drugs) were not universally reported. Furthermore, the event rates differed by a factor of 2 between the two studies. Similar to what Singh et al. reported, appropriate shocks reported after an ischemic event occurred within 40 days in a European cohort investigated by Kondo et al. (not fulfilling inclusion criteria for primary analysis of this study) [
Lamichhane et al., on the contrary, specifically investigated the use of WCD beyond three months. In their study population, 35% had ICM, and the main reason for prolonged use was ongoing evaluation for ICD implantation. Only 6 patients received appropriate shocks in this cohort, and the authors, however, did not report the time of the events/shocks [
The reported wear time for NICM was generally longer compared to ICM in the reviewed studies [
In light of the DANISH study [
A further analysis from the WEARIT-II registry investigated patients using the WCD beyond 90 days and found a higher rate of extended use in NICM patients and furthermore discovered a further improvement in EF and thus obviating the need for an ICD in one-third of their patient cohort [
Another possible indication for WCD use is PPCM, which however may have been reported in previous cohort investigating NICM as well. Duncker et al. provided the study examining only patients with PPCM [
Current ESC guidelines recommend ICD implantation following standard guidelines for NICM, but also refer to WCD treatment (recommendation level class IIb). This is particularly noteworthy since EF recovery can be expected in a high rate of PPCM patients [
Data regarding WCD use and device removal were available in 6 studies, while Tanawuttiwat et al. only examined this cohort [
Bridging the time to heart transplantation is another possible indication for WCD use [
There are other, less frequent indications for WCD use. Wan et al. investigated patients on hemodialysis [
Myocarditis was infrequent in the reviewed studies. Only two studies were reported on wear time [
Few patients with channelopathies or congenital heart diseases were included in the assessed studies [
Another population who may benefit from an extended use of WCD is children and younger adults. While they may have the highest lifetime benefit of an ICD implantation if indication is made correctly, they are also at higher risk of ICD complications such as multiple battery changes and thus increased risk of infection. Collins et al. examined a population ≤21 years of age with a WCD use for any indication. The main causes of increased arrhythmogenic risk were cardiomyopathy, primary arrhythmia (without specification), and congenital heart disease especially in the ≤18 years of age cohort. Since at the end of their study only 32% of patients had an ICD implanted, prolonged WCD use might be justified [
Several patient populations were reported to use the WCD for an extended period. Some subgroups were more prevalent probably due to the (assumed) reversibility of their elevated arrhythmogenic risk. In general, patients not yet receiving an OMT deserve a chance to improve their ejection fraction while being protected from SCD events. Patients possibly benefiting prolonged use after review available literature may be patients with PPCM and young patients in order to avoid unnecessary ICD implantation. These patients may be at higher risk of dying from SCD than dying of other cause, yet ICD implantation should be carefully evaluated after establishing OMT.
Clinicians also have to take into account patients’ choice to refuse ICD while accepting a longer WCD use. The prolonged use of WCD in patients with NICM seems less clear particularly due to low treatment rates reported. There are several disadvantages of a prolonged WCD use. Wear comfort is an obvious problem especially over longer periods. The absence of pacing modalities (for bradycardia, antitachycardia pacing, or postshock pacing) can be an issue and fail to prevent SCD due to asystole. Lastly, a cost-benefit analysis is necessary to justify a longer WCD use.
Our analysis has several limitations. The heterogeneity of clinical studies, which resulted in missing data on the time of appropriate shocks, is a limitation of this study. 11 of the 14 studies reported the database kept by ZOLL. It is therefore possible that patients fulfilling inclusion criteria for more than one of the listed studies in Table
Extended use of WCD is commonly reported in reviewed literature, although majority of it is of descriptive nature. Patients most likely to wear the device longer than 3 months seem to be patients with NICM, specifically PPCM likely due to the lack of other significant comorbidities and the high rate of disease improvement beyond the first 3 months often obviating the need for ICD implantation. On the contrary, patients listed for heart transplantation could also benefit from prolonged therapy to avoid risks of the more invasive ICD implantation. Question remains, however, what the rate of appropriate shock is during this prolonged use, if a true benefit is present compared to ICD implantation. To assess this true benefit, prospective and randomized data are needed.
The data used to support the findings of this study are included within the article.
The authors declare that they have no conflicts of interest.