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Abstract
Introduction Wearable cardioverter-defibrillators (WCD) have emerged as a valuable tool in the management of patients at risk for life-threatening arrhythmias. These devices offer a non-invasive and temporary solution, providing continuous monitoring and the potential for prompt defibrillation when needed. In this study, we explore the use of WCD and evaluate arrhythmic events through comprehensive monitoring.
Methods From November 2022 to May 2024, we conducted an outpatient follow-up of 41 patients receiving WCD. Regular check-ups, remote monitoring and comprehensive echocardiography were performed to optimise a tailored therapy.
Results The average age of the patients was 59.2.4±16.5 years, with 78% being male. Among the cohort, 54% had hypertension, 41% were smokers and 66% had dyslipidaemia, while 27% were diabetic. WCD was assigned according to the Italian Association of Hospital Cardiologists position paper focussing on the appropriate use of WCD and European Society of Cardiology guidelines on ventricular arrhythmias and the prevention of sudden cardiac death: 24 (58%) patients had a de novo diagnosis of heart failure with reduced ejection fraction, 11 (27%) patients had a recent acute coronary syndrome and ejection fraction <35%, 3 (7%) patients had a cardiac electronic device extraction and 3 (7%) patients had myocarditis with features of electrical instability. The average follow-up was 62±38 days according to specific aetiology, with a daily wearing time of 22.7±1.3 hours. No device interventions were recorded. At the end of the follow-up period, 15 patients still required an implantable cardioverter-defibrillator (ICD). Among these, 12 patients (29%) underwent ICD implantation. Two patients (5%) declined the procedure.
Conclusions The use of WCD for patients at high risk of arrhythmias allowed to optimise therapy and limit the indications for ICD. Inappropriate implantation of ICD was avoided in 69% of patients who received WCD. The device showed a good safety profile, low incidence of device interventions and adequate patients’ adherence to WCD use.
- SUDDEN CARDIAC DEATH
- Defibrillators, Implantable
- Heart Arrest
Data availability statement
Data are available upon reasonable request.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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WHAT IS ALREADY KNOWN ON THIS TOPIC
Wearable cardioverter-defibrillators (WCD) are recognised as a non-invasive, temporary solution for patients at risk of life-threatening arrhythmias, offering continuous monitoring and prompt defibrillation capabilities. Their role in optimising patient management and potentially reducing the need for implantable cardioverter-defibrillator (ICD) implantation has been established.
WHAT THIS STUDY ADDS
This study demonstrates that WCDs can provide innovative remote monitoring data and significantly reduce the inappropriate implantation of ICDs. It also confirms a good safety profile and high patient adherence to WCD use.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
These findings support wider implementation of WCDs in clinical practice to improve patient management and decision-making regarding ICD implantation, as well as the potential value of remote monitoring provided by the device.
Introduction
Sudden cardiac death (SCD) continues to pose a significant global health challenge, resulting in the cause of death for millions of people annually.1 While implantable cardioverter-defibrillators (ICD) have served as a cornerstone in preventing SCD among high-risk individuals,2 there are instances where the arrhythmic risk may be transient and ICD implantation potentially avoidable depending on the clinical course. This may be observed within the first 40 days postmyocardial infarction or after the initiation/during the titration phase of medications used in de novo diagnosis of heart failure with reduced ejection fraction (HFrEF) or during the inflammatory healing processes, such as in myocarditis with electrical instability. Wearable cardioverter-defibrillators (WCD) have emerged as a useful tool in clinical practice to manage SCD risk while waiting for possible ventricular systolic function recovery, demonstrating safety and reliability in protecting against SCD across various pathological conditions.3 The use of WCD can allow the attainment of optimised medical therapy (OMT), safeguarding against potential arrhythmic risks for extended follow-up periods exceeding 6–9 months, thereby reducing inappropriate ICD implantation and the associated infectious risks linked with the devices. The objective of our study is to assess after WCD usage the persistence of indications for ICD implantation in a real-world population across different pathological conditions, leveraging the multiparametric remote monitoring provided by WCD.
Methods
Population and inclusion criteria
This is a prospective observational cohort study conducted between September 2022 and May 2024 in the cardiology unit of San Filippo Neri Hospital. A total of 2802 patients were admitted to our cardiology department during the study period. Of these, 384 patients presented with new-onset left ventricular dysfunction with ejection fraction (EF) <40% or electrical instability requiring monitoring were screened for possible WCD use. Patients already implanted with ICD and those who received the device during the same hospitalisation were excluded. In addition, patients considered unsuitable due to contraindications to WCD (disabled patient, lack of adherence to care, lack of caregiver or social support network), the need for antibradycardia therapy or that refused WCD use were excluded (figure 1). Eligible patients provided consent for device deployment according to the criteria reported in the Italian Association of Hospital Cardiologists (ANMCO) position paper for appropriate WCD usage3 and European Society of Cardiology (ESC) guidelines for ventricular arrhythmias and SCD prevention.4 Inclusion criteria comprised patients with de novo diagnosis of HFrEF (regardless of the aetiology, ischaemic or non-ischaemic), acute coronary syndrome (ACS) with reduced EF or patients who have undergone device explantation and require time before reimplantation with an indication for either ICD evaluation or resynchronisation therapy in primary or secondary prevention. Additionally, patients with myocarditis and positive cardiac MRI (CMR) showing features predisposing to electrical instability were included.
The diagram shows the patient selection process for the wearable defibrillator use.
WCD characteristics and parameters
The WCD system consists of a wearable vest integrated with four ECG detection electrodes and three defibrillation therapy delivery ‘plates’ connected to a battery-powered monitor.5 The recordable ECG comprises two bipolar traces acquired through the four detection electrodes placed on the chest surface in anterior-posterior and lateral-lateral positions. Each patient candidate for WCD use received training from medical personnel and support specialists upon device delivery. In cases of poor compliance or lack of self-sufficiency, relatives or caregivers were trained. In addition to arrhythmic events, daily heart rate, physical activity, body position during the day and nighttime rest and WCD-wear-time were recorded. Furthermore, the WCD was programmed to conduct a weekly 6-min walk test (6MWT) to assess progress in physical endurance and patient autonomy. Through WCD algorithms, distances travelled, symptoms and heart rate before, during and after exercise were assessed.6 Additionally, patients were prompted weekly to complete a modified Minnesota Quality of Life questionnaire to evaluate health status, symptoms, therapy adherence, the presence of lower extremity oedema and weight changes through simple yes/no questions or numeric scale ratings.3
Follow-up
The duration of follow-up varied based on the pathology underlying the indication for WCD use. Patients’ ECG traces, WCD alarms and multiparametric data acquired by the device allowed remote monitoring of patients. Scheduled automatic and manual transmissions were analysed daily by specialised healthcare professionals. 30–40 days after discharge from the index event during which the WCD was placed, patients underwent outpatient evaluation, including a comprehensive physical examination, symptom assessment, ECG and echocardiogram. Medical therapy was managed according to guideline recommendations and preferred single pill combinations, when available, to achieve greater adherence to treatment.7 In cases of evident recovery of EF (an increase of at least 10% with EF >40%) and clinical-functional parameters, the WCD use was discontinued; otherwise, the device was retained and therapy titrated for re-evaluation at a distance of at least 4 weeks. For patients with a de novo diagnosis of HFrEF or WCD, it was maintained for up to a maximum of 3–6 months and a second check-up was scheduled between 60 and 90 days to assess the recovery of EF and a minimum increase of at least 10% and >40%. Patients with electrical instability or prior CMR evidence of myocardial oedema, grey zone or suggestive T1 and T2 mapping values of acute inflammatory processes underwent repeated CMR within 3–6 months before the WCD was discontinued.
Statistical analysis
Descriptive statistics are presented as means±SD for normally distributed continuous variables or as medians with IQR for non-normally distributed data. Categorical variables are presented as absolute numbers (percentages). The normality of distribution was assessed using the nonparametric Kolmogorov-Smirnov test. Differences between means were assessed using the t-test for normally distributed variables, with the F-test used to assess the equality of variances. For non-normally distributed variables, the nonparametric Mann-Whitney test was employed. Proportional differences were evaluated using either χ2 analysis or Fisher’s exact test as appropriate. The analysis of variance, followed by Dunnett’s two-sided post hoc test for multiple comparisons, was used. A significance threshold of p<0.05 was applied to all tests. Statistical analyses were conducted with STATA statistical software, V.16.0 (College Station, Texas, USA: StataCorp).
Results
A total of 41 patients with WCD were enrolled in this study. Patients’ general characteristics, risk factors, therapies and indications for WCD are summarised in table 1. WCD was prescribed in cases of de novo diagnosis of HFrEF in 24 (58%) patients, recent ACS with EF <35% in 11 (27%) patients, cardiac electronic device extraction in 3 (7%) patients and myocarditis with electrical instability in 3 (7%) patients. The average follow-up duration was 62±38 days according to specific aetiology and clinical/systolic function evolution, with a daily wearing time of 22.6±1.6 hours.
Clinical and echocardiographic (at the beginning and the end of the follow-up period) characteristics of the entire study cohort and different patient groups according to the indication for the wearable defibrillator are reported
Medical therapy
Patients were in OMT at discharge tailored to their specific comorbidities, with therapy titrated during outpatient follow-up or through remote visits with the support of telemetrically monitored parameters. Overall, 90% of patients were on renin-angiotensin-neprilysin system inhibitors (angiotensin-converting enzyme inhibitors, angiotensin receptor antagonists and angiotensin receptor-neprilysin inhibitors), 95% on beta-blockers, 76% on mineralocorticoid receptor antagonists, 76% on sodium-glucose cotransporter-2 inhibitors and 27% on antiarrhythmic drugs.
Echocardiography
The echocardiographic parameters recorded during follow-up showed a general improvement in EF in patients with de novo diagnosis of HFrEF and patients with ACS with EF <35%, as well as a reduction in indexed ventricular volumes.
Cardiac MRI
Patients with CMR presented features of regional wall motion abnormalities with diastolic function abnormalities in one patient. In all patients with myocarditis, CMR showed signs of oedema, hyperaemia or late gadolinium enhancement in typical patterns of myocarditis. T2-based imaging showed high T2 signal intensity, with a global T2 signal intensity ratio of ≥2, or increased myocardial T2 relaxation times. Increased T1 relaxation times were also reported, as well as extracellular volume size.
Outcomes
The parameters monitored remotely are summarised in table 2. No device interventions for sustained ventricular arrhythmias were recorded. Non-sustained arrhythmic episodes, particularly monomorphic ventricular tachycardia, and ventricular extrasystoles, were observed in up to 12% of patients.
Key parameters monitored remotely
At the end of the follow-up period, 15 patients required an ICD. Among these, 12 patients (31%) underwent first ICD implantation, and 3 underwent ICD reimplantation. The Minnesota Quality of Life Survey and the 6MWT performed during the follow-up showed a trend towards symptom improvement and increased functional capacity, respectively. A summary of remote monitoring, with data, a functionality test and a questionnaire, is reported in figure 2.
The main parameters monitored remotely by wearable defibrillators are summarised in the figure. (A) Wear time and summary of patient activity trends are shown at the top, while below are graphs of trends in heart rate, footstep activity and body position during 60 days of follow-up. In this case, it is worth noting how, as a result of increased heart rate in mid-April, remote intervention with titration of beta-blocker therapy led to a reduction in heart rate over the next 30 days. (B) The panel reports the health questionnaire with 11 items submitted to the patient by the device. The questionnaire provided information on functional capacity. (C) The progress of walking tests during the period examined. A progressive increase in the distance walked is reported against a stable heart rate and in the absence of symptoms.
The comparison between patients implanted with ICD at the end of follow-up and patients who didn’t need the implantation is shown in table 3. Clinical characteristics and clinical history were similar, as were the echocardiographic characteristics, except for the EF. Treatment adherence was similar, whereas, during the use of WCD, arrhythmia episodes without intervention were recorded more frequently in the implanted group (33% vs 4%). Finally, the majority of patients from the implanted group had HFrEF as their main indication (83% vs 54% p<0.001), while the majority of patients with ACS indication improved EF significantly and were not candidates for ICD implant (17% vs 35%, p<0.001).
Comparison of final follow-up between ICD-implanted and WCD-returned patients
Discussion
The present study investigated the utility of WCDs in a real-world population encompassing various aetiologies for reduced left ventricular EF (LVEF) and electrical instability, potentially deferring or avoiding ICD implantation. Our findings demonstrate the effectiveness of WCD in safeguarding patients against SCD while enabling tailored OMT optimisation and comprehensive remote monitoring. Notably, a significant proportion (69%) of patients no longer required ICD implantation after the WCD follow-up period, highlighting the potential for WCD to refine risk stratification and reduce unnecessary device implantation. Over the past decade, observational studies have generally found WCD to be both safe and effective for terminating ventricular arrhythmias, particularly in cases of HFrEF. However, the only randomised controlled trial that tested the WCD, the VEST trial, did not demonstrate an improvement in patient survival.8 A per-protocol analysis of the VEST trial showed a significant reduction in all-cause and arrhythmic mortality.9 The poor compliance of patients enrolled in the trial was one of the main reasons for the study’s low success, as well as for a significant crossover between study groups. In the per-protocol analysis, WCD compliance was independently predicted by cardiac arrest during myocardial infarction, diabetes, previous history of heart failure, EF ≤25%, centre of enrolment and the number of WCD alarms, while worse compliance was predicted by family status, Asian race, higher body mass index, previous percutaneous coronary intervention or any WCD shock. Consequently, recent guidelines recommend WCD use only in specific settings. Emerging data suggest that WCD might also be valuable for monitoring patients similar to what has already been observed with ICD,10 which could be particularly beneficial in cases of newly diagnosed heart failure.11 12 In the management of heart failure, especially new-onset heart failure with left ventricular dysfunction, WCD may serve multiple roles: as an educational tool, a monitoring device and a preventative measure against sudden cardiac death.13 WCD can function as a telemonitoring system, aiding in supervising, reminding and training patients, as well as motivating them to maintain or increase physical activity. Beyond the primary role in detecting and treating life-threatening arrhythmias, WCD is capable of monitoring physiological parameters. In our study population, we exploited the device’s monitoring potential by analysing heart rate, footsteps as an indicator of activity and body position to monitor any postural changes associated with heart failure symptoms. In addition, the 6MWT and health questionnaire were performed to monitor patients’ functional capacity and guide targeted interventions if necessary. The importance of these assessments was shown in a previous study that observed a decrease in physical activity, measured by step counts, in patients before the occurrence of ventricular arrhythmias.14 Another study reported that patients who are overweight or obese showed decreased physical activity and may potentially benefit from the short-term physician’s intervention and also reported that changes in sleeping angle or position may indicate the worsening of heart failure, leading to the need for intervention.15 However, at present, there is no standardised use of these parameters, which are available in addition to the main function of the device. At times, the indication for monitoring with the WCD rather than immediate implantation of an ICD may be questionable, also given the non-negligible costs that its use for more than 90 days may entail,16 whereas some authors also debate whether it is always appropriate to wait at least 40 days from the acute event for ICD implantation.17 Therefore, compared with ICD costs, WCD may not seem like an effective choice. However, with the implantation of ICD, the costs associated with subsequent replacements must also be considered, as well as the costs of follow-ups, remote monitoring and any potential complications,18 which represent the major expense factor associated with the electronic cardiac devices themselves. Data from the Danish ICD Register19 showed that in SCD primary prevention, appropriate and inappropriate ICD shock occurrence was significantly lower than that reported in randomised trials, and dual-chamber devices were associated with a greater risk of inappropriate shocks as compared with single-chamber ICD. Given the low real-world intervention rate of ICD in primary prevention,20 21 it is important to try to optimise implantation through a multiparametric analysis that can stratify patients’ risk of SCD by considering the potential impact of device implantation.22 In this context, the use of WCD could reduce the costs of hospital stays in patients with ventricular dysfunction.23 WCD enables patients to be safely moved to less intensive monitoring wards and may reduce days spent in the acute coronary care unit while protecting against SCD.24 Consequently, WCD helped avoid unnecessary ICD implantations, with half of the patients experiencing LVEF improvement, thereby enhancing quality of life and reducing healthcare expenses.24 Similar results are also obtained in our study, in which extended observation periods and more appropriate ICD implantations were performed, with 69% of patients at the end of follow-up showing significant improvement in ventricular function, and only in less than one-third of cases ICD was implanted. These data were recently confirmed by a multicentre study, the follow-up of which showed that titration of therapy under WCD protection reduced ICD implantation in 77% of cases.25 Consistently with the data reported previously in the literature,26 in our study, men were more represented than women, and between sexes, no differences were found in adherence to treatment. There were no differences in adherence even by age, despite some studies reporting higher compliance for elderly patients and lower average total hours of device use in young patients.27 Older patients are known to have good compliance with WCD, have more frequent ventricular arrhythmias, and are more likely to receive an ICD at the end of WCD use.28 In our cohort, ventricular tachycardia events occurred in one-third of the cases of patients who went to ICD implantation versus a very small percentage of the group not undergoing ICD. For both, the mean age was close to 60 years, in agreement with the prevalent aetiology among patients represented by DCM in 58 %, while post-ACS left ventricular dysfunction accounted for 27%. Although limited in our patients, there were also some cases of myocarditis with electrical instability documented by non-sustained ventricular arrhythmias and CMR positivity for features typical of an acute inflammatory process. It has been recognised that arrhythmia risk is particularly high during the acute phase of myocarditis in the presence of marked left ventricular dysfunction.29 Since most patients with myocarditis have a good long-term prognosis with improved left ventricular function,30 possible ICD implantation should be procrastinated until the end of the acute phase, and WCD fulfils this need during the healing process.31
Our study has some limitations. The relatively small sample size and single-centre design warrant larger, multicentre trials to confirm our observations. Long-term data on the impact of WCD use on patient outcomes and healthcare resource utilisation would be valuable. The cost-effectiveness of WCD therapy compared with upfront ICD implantation warrants further investigation. Our findings suggest that WCD can reduce unnecessary ICD implantations and associated healthcare costs by enabling better risk stratification and monitoring. Future research should evaluate the economic implications of this approach, considering the costs of device replacements, follow-ups and potential complications associated with ICD. Furthermore, the potential use of artificial intelligence algorithms to analyse WCD-derived data to enhance risk stratification and arrhythmic event prediction holds promise. The integration of WCD data with other clinical parameters and real-world data sources could pave the way for the development of personalised risk prediction models and further refine patient management strategies.
Conclusion
In conclusion, the WCD proved to be a safe and effective tool in our study population, which included patients with various aetiologies of reduced LVEF and electrical instability. Multiparametric evaluation and remote monitoring facilitated pharmacological therapy titration with optimal safety. The appropriate use of WCD reduced the need for ICD implantation.
Data availability statement
Data are available upon reasonable request.
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants. This is a observational study conducted according to the standards of good clinical practice and the declaration of helsinki. Participants gave informed consent to participate in the study before taking part.
Acknowledgments
We would like to express our thanks to the nursing staff for their constant support in daily clinical practice.
References
Footnotes
Contributors Conceptualisation: FC and AM; methodology: CP and SA; validation: SDF; investigation: SA; data curation: AM; writing and original draft preparation: AM and SDF; review and editing: AA, CP and FN; supervision: FC. All authors have read and agreed to the published version of the manuscript. AM is responsible for the overall content as guarantor.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.