In this retrospective analysis from a single cardiac surgery center in Germany, safety, effectiveness, and compliance of WCD use were investigated in patients after cardiac surgery in a real-life setting. The presented data complement the study results of a recent, large German multi-center study reported by Kuehn et al. 
In post-surgical patients, the temporary use of WCD is particularly warranted in patients at high risk for SCD. In our study population, 50 (90.9%) patients had an LVEF ≤ 35% after surgery and were, therefore, by broad consensus, at high risk for SCD. A substantial number (n = 4, 7.3%) of the study patients experienced VT episodes while wearing the WCD. In these patients, as expected, the first VT episode occurred within 3 months (14–58 days) after surgery. In 2 patients (3.6%) the WCD registered a life-threatening VT warranting an intervention and successfully delivered a defibrillation shock in both cases. During the observational time, none of the WCD devices delivered inappropriate shocks. In four instances, shock delivery was not necessary, and VT episodes were, correctly not treated. These findings on the effective delivery of shocks are in line with the recently published German multi-center study, which included 1168 patients using WCD after cardiac surgery . In the multi-center study, 9.1% of the patients experienced VT/VF episodes. Almost all episodes (93.2%) occurred within the first three months after surgery. 1.5% of the patients required a shock delivery. 0.7% received an inappropriate shock.
In approximately half of the patients in our study, a prophylactic ICD implantation was eventually not necessary due to a clinically relevant improvement of LVEF. This observation is in line with prior data and strengthens the role of a WCD as a crucial bridging therapy during the waiting time until a final decision on the need for an ICD can be made and particularly during the high-risk postoperative period. The ESC has clearly pointed out the need for temporary protection from SCD by a WCD, especially in patients after cardiac surgery [10; 9]. Notably, ICD implantation remains a necessity for many patients due to ongoing symptomatic heart failure and LVEF ≤ 35% despite ≥ 3 months of medical treatment . In our study, one-third of the patients had to undergo ICD implantation.
There were differences shown in the further clinical course between patients < 60 and > 60 years. The data show that the proportion of patients with an EF > 35% at < 60 years increases from 21.4–67.9%, while at > 60 years, it only increases from 22.2–48.1%. We couldn’t have a clear clue why that happened regarding this data. That is why we designed a prospective observational study that should be completed in the next five years to address whether the patient's physical activity after the operation might influence the recovery of the myocardium.
To ensure high effectiveness, the continuous wearing of the WCD is one of the main requirements for effective protection from SCD . In this real-life setting, WCD-wearing compliance of patients in post-surgery care with transient risk for SCD was very high, as the device was worn on almost all days (96%), with an average daily wearing time of more than 23 hours. These findings are in accordance with previous studies on patients using a WCD [14; 16].
Strengths and limitations
A limitation of this study is the rather low number of patients from a single cardiac surgery center, making comparisons between subgroups difficult. However, our study still gives valuable insight in the efficacy of the WCD in a real-life setting. Moreover, our study supports the reported findings of a large German multi-center study .