How good is your life vest in the real world?

Wearable cardioverter defibrillator (WCD) can be thought of as a life vest till the lifeboat (implantable cardioverter defibrillator ICD) arrives [1]. It is often used as a bridge to the implantation of an ICD when the indication for the latter is not yet well established in the subject. Sometimes it may be used as definitive therapy in those with limited life expectancy due to other serious comorbidities. Yet another reason to use a WCD is when an ICD has been explanted following infection and one is waiting for the infective process to settle. In concept, theWCD is an ideal device for all these situations. We do have enough clinical trial data supporting the use of WCD for various indications [2]. Naniwadekar A and associates have reported the real world utilization of the device in a community setting, in this issue of the Journal [3]. They evaluated a total of 140 patients of which 46% had nonischemic cardiomyopathy (NICM) and 32% ischemic cardiomyopathy (ICM). There were a few with genetic predisposition for sudden cardiac death and some in whom an ICD had been explanted. Cumulatively, they have presented the data for 21 patient years, with a median usage per patient of 43 days. Daily mean use was 17.3 ± 7.5 hours. This was lower than the real world data presented by Dillon KA et al. [4], where the daily usage was 21.3 hours (range of 0e23.9) among 2105 patients. Ethnic distribution of the patient population was grossly skewed, with 85.9% belonging to the African American race. This, the authors mention as representing the distribution in the community to which their institution caters. Skewed racial distribution may have some effect on the generalizability of their results. The predominance of NICM over ICM in their study group is also possibly related to the higher prevalence of NICM in their setting. WEARIT-II Registry on real world usage of WCD, had 46% of NICM and 40% ICM among their 2000 participants [5]. The total number of shocks, both appropriate and inappropriate, were small, due to the lower number of total subjects in the study. Out of the 6 shocks, 2 were appropriate and 4 inappropriate. This 2.8% inappropriate shock rate was much higher than the 0.5% reported from WEARIT-II Registry [5]. But the gross difference in the number subjects (140 vs 2000) prevents any meaningful comparison between the two studies. No appropriate shocks were noted in the ICM group, while 2 in the NICM group received appropriate shocks. Both of them had QRS widening and belonged to the African American race. One of them had an ICD implantedwhile the other recovered left ventricular function sufficiently to be moved out of ICD indication. One patient with NICM and another with recurrent syncope and