Wearable Cardioverter Defibrillator ― Initial Experience in the Outpatient Setting in Japan ―

Background: The wearable cardioverter defibrillator (WCD) has been available since 2014 in Japan, and its benefit in the in-hospital acute phase at high risk of ventricular tachyarrhythmia (VTA) has been established, but its clinical use in the outpatient setting remains unclear, especially in Japan. Methods and Results: The subjects consisted of 43 consecutive patients with WCD use in the outpatient setting from April 2014 to October 2019 at the present institute. Event alerts and wearing compliance were checked via the remote monitoring system, and a dedicated WCD training team contacted the patients if necessary. The median observation period was 51 days (IQR, 37-68 days) and the median daily wearing time was 23.1 h/day (IQR, 22.0-23.6 h/day). WCD was prescribed for primary prevention of VTA in 7 patients (16%), and for secondary prevention in 36 (84%). The common reason for WCD use was preventive therapy and/or clinical observation. Two appropriate and one inappropriate shock were observed. Eleven patients were not indicated for ICD because of successful catheter ablation optimal medical therapy, VTA in early onset of heart disease and refusal. The remaining 32 patients, however, underwent ICD implantation. Conclusions: In the present real-world study, the WCD wearing compliance was well-maintained in the outpatient setting. WCD is useful for patients at high risk of VTA.