prevent scd in patients until it is clear that a patient's heart issues are indeed permanent and long-term protection with an icd must be applied. temporary living with the wcd the wcd allows patients at high risk for scd who are discharged from the hospital to return to most of the normal daily activities without constantly worrying about their heart issues and possible fatal outcomes. a retrospective study investigating quality of life in patients who had been fitted with a wcd found that the majority did not feel any impairment in terms of mobility (68%), self-care (83%), daily routine (75%), pain (64%) and mental health (57%). another prospective study evaluating depression and anxiety in patients eligible for wcd found a trend for better improvement of depression scores in patients who actually received the wcd. currently a study on the use of the wcd started in uk. in case of questions concerning which activities are possible, the manufacturer recommends consulting with the treating physician. the manufacturer also advises to avoid activities in loud and/or high vibration environments due to the possibility of missing an alert from wcd. assessment of usefulness the wearable cardioverter defibrillator is an option for patients who are at risk for sudden cardiac arrest (sca) and are not candidates for or who refuse an implantable defibrillator. some cardiologists agree that a wearable cardioverter defibrillator is medically only necessary, compared to standard medical treatment for a subset patients at risk for sca, however medical guidelines give a clear understanding of the right diagnosis with benefits for the wcd. in january 2018, the fda issued a safety alert related to a known malfunction in some units which could prevent the wcd from delivering a treatment shock. zoll had previously issued (in september 2017) a communication instructing users to return the devices for replacement if a specific error message was visible, this indicating the malfunction. copies of the alert were included in all subsequent shipments of the device. the results of a randomized controlled trial were presented at the american college of cardiology’s 67th annual scientific session (in the spring of 2018). the study results apparently did not show sufficient evidence in the primary outcome to show the wcd reduced sudden cardiac death in post-heart attack patients. in the group that wore the wcd, 1.6% died from sudden cardiac arrest, and in the group that didn't wear the wcd, 2.4% died, which is arguably not a statistically significant difference. indications for receiving a wcd the wcd is generally recommended as temporary therapy for all patients who are at risk of scd and can be prescribed in uk as a monthly rental device. according to the international guidelines of acc/aha/esc in 2006, the esc in 2015 and 2021 as well as aha/acc/hrs in 2017 patients that may benefit from a wcd include: patients with reduced left ventricular pump systolic function (lvef) of ≤ 35% in the first 40 days after a myocardial infarction (mi) without revascularization in the first 90 days after coronary revascularization with coronary artery bypass graft (cabg) in the first 90 days after percutaneous coronary intervention (pci) newly diagnosed ischemic heart failure patient with reduced ejection fraction (hfref) for at least 90 days of optimal medical therapy patients with ventricular fibrillation (vf) or sustained ventricular tachycardia (vt) spontaneous or inducible occurring later than 48 hours after mi patients on the waiting list for a heart transplantation bridging the waiting time for patients with indicated or interrupted icd therapy (e.g., icd explanted due to infection or intolerance and pending potential re-implantation, delayed implantation due to medical reasons including infection, recovery from surgery) with ongoing heart failure medication that needs adjustment with inflammation of the myocardium/myocarditis and waiting for resolution with familial or genetic risk for scd if diagnostics have not yet been completed and/or an icd has been ruled out newly diagnosed non-ischemic heart failure patient with reduced ejection fraction, including dilated cardiomyopathies (dcm) and new york heart association (nyha) stage ii-iii heart failure patients patients in a risk phase of pregnancy cardiomyopathy (peripartum cm/ppcm) the ishlt has listed the wcd as a class i recommendation in its guidelines for the care of cardiac transplant candidates since 2006. this means that patients waiting for a heart transplantation who are discharged from hospital should receive a wearable defibrillator to bridge the waiting time until receiving the transplant. the wcd is one of the procedures or treatments for which there is evidence and general agreement that it is beneficial, useful and effective in the given condition. wcd has also been used in the specific circumstance where patients have an icd but require temporary explantation for radiotherapy in the location of the icd generator. clinical trials on the efficacy of the wcd after european ce-certification and fda approval of wcd (lifevest®), a number of retrospective and prospective registries verified the efficacy and safety of the wcd. data from more than 30,000 patients who have used the wcd are published for an expansive variety of indications. in the following only an excerpt is presented. meta-analyses a meta-analysis of 11 comparable studies with approximately 20,000 non-overlapping patients in different indications was published by nguyen et al. they found an overall mortality rate of 1.4%, a vt/vf rate of 2.6% and a vt/vf-related mortality rate of only 0.2% across all patients. 1.7% of the patients (9.1 patients/100 patient years) had received an appropriate treatment, which was successful in 96%. the inappropriate shock rate was <1.0%. a systematic cross-indication review and meta-analysis of studies reporting treatment rates of wcd was conducted by masri et al. in 2019. they analysed 28 studies and over 30,000 patients. over a period of 3 months, 5 per 100 patients received appropriate wcd treatment shocks, and only 2 per 100 patients received inappropriate treatment shocks. analyses of selection or publication bias (e.g., egger-test) revealed, that there were no differences between independent and manufacturer-sponsored studies, and no differences between prospective and retrospective studies. according to the authors, the rate of patients, who were appropriately treated with the wcd over 3 months of follow-up, was substantial and much higher in observational studies compared to the rct included in the analysis. the mortality rate was very low at 0.7 per 100 patients over 3 months. randomized controlled trial data overview of all analyses from the vest study concerning mortality rates the first and to this date only randomized controlled trial (rct) on wcd use with post-mi patients is the vest trial, which was first published by olgin et al. in 2018. in total 2,302 patients were included in the intention-to-treat (itt) analysis. the primary outcome of the vest-study, arrhythmic mortality, was 1.6% in the wcd group vs. 2.4% in the control group. the difference was not significant despite a 33% relative risk reduction (rrr). the secondary outcome of the vest-study, all-cause mortality, was 3.1% in the wcd group and 4.9% in the control group. the difference was significant with a 36% reduction in mortality (rrr). notably, in this study the average daily wearing time was only 14 to 18 hours/day, hence much lower than supposed according to observational studies. an additional as-treated analysis (att) provided as supplemented appendix to the original publication, revealed statistical significance in all mortality endpoints, thus positive results for the use of the wcd. in a per protocol analysis (ppa) published in 2020, the reduction in arrhythmic mortality was 62% and in all-cause mortality 75%, both significant results, which is comparable to the results shown in the att analysis. these results indicated that the wcd is highly effective in reducing mortality rates in patients with a high risk for scd. essential factors in successful wcd therapy in everyday clinical practice are high wearing compliance and the use of the monitoring system provided by the manufacturer (zpm network). health technology assessments (hta) aidelsburger and colleagues published the results of an hta in 2020. the authors analysed data from 49 studies and concluded the wcd is a safe and effective intervention in cases of sudden cardiac arrest during the time needed for determination of long-term risk management strategies, that the wcd is reliable in detecting vt/vf events and shows a high rate of appropriate shocks which lead to a high rate of successful vt/vf terminations. cortesi and colleagues published the results from another hta in 2021. they focused on cost-efficacy comparing the wcd to “standard of care” in patients at risk for scd after mi or icd explantation. the authors found that the wcd is a cost-effective treatment option in patients after mi using the data from the vest study. in patients after icd explantation the wcd provided even a cost saving of €1,782 compared to 3 weeks hospitalization in a low intensity hospital (standard of care) using data from the italian nhs. the authors concluded that for the italian nhs the wcd use contributes to a more effective utilization of resources and to the improvement of patient care in clinical practice. currently an hta is planned to be conducted in uk. notes sharma, parikshit s.; bordachar, pierre; ellenbogen, kenneth a. 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