Mechanism, follow-up and recurrence of inappropriate therapy in the PRAETORIAN trial: action reduces recurrence
Authors: Pepplinkhuizen S , Delnoy PPHM , Olde Nordkamp LRA , Kuschyk J , Bonnemeier H , Bijsterveld NR , Boersma LVA , El-Chami MF , Smeding L , Van Der Stuijt W , De Weger A , Richter S , Betts TR , Wilde AAM , Knops RE 
Published: May 2022

Abstract

Funding Acknowledgements
Type of funding sources: Private company. Main funding source(s): Boston Scientific Corporation

Background
The PRAETORIAN trial demonstrated that the subcutaneous ICD (S-ICD) is non-inferior to the transvenous ICD (TV-ICD) with regard to inappropriate shocks (IAS) and complications. Inappropriate therapy is an undesirable side effect of ICD therapy.

Purpose
This pre-specified secondary analysis evaluates all inappropriate therapy in the PRAETORIAN trial and subsequent action to reduce recurrence of IAS.

Methods
The PRAETORIAN trial is an international, multicentre, randomised trial, which included patients with an indication for ICD therapy. In total, 849 patients were randomised to receive an S-ICD (N=426) or TV-ICD (N=423). ICD programming was mandated by protocol. Inappropriate therapy was defined as any ICD therapy on a different rhythm than ventricular tachycardia or ventricular fibrillation. A day with inappropriate therapy was defined as all device episodes on the same day. Mechanism, actions and recurrence rate were determined using days with inappropriate therapy.

Results
In the S-ICD group, 42/426 (10%) patients received inappropriate therapy, compared to 42/423 (10%) patients in the TV-ICD group (P=0.97). In total, 41 patients in the S-ICD and 29 patients in the TV-ICD group received at least one IAS (P=0.14). The total number of IAS in the S-ICD and TV-ICD group is comparable (124 vs. 130, P=0.88). The most common underlying mechanism of inappropriate therapy was T-wave oversensing in the S-ICD group (45%) and a supraventricular tachycardia (SVT) in a therapy zone in the TV-ICD group (93%). When no action was undertaken after the first IAS, the recurrence rate of an IAS of the same etiology was 56% (5/9) in the S-ICD group and 50% (4/8) in the TV-ICD group. An action, such as a change in medication, a change in programming, an invasive action or lifestyle advise resulted in a recurrence rate of 23% (7/30) in the S-ICD group and 30% (6/20) in the TV-ICD group. The recurrence rate was significantly higher when no action was undertaken versus any action (P=0.04) (Figure 1.). A change in programming resulted in a lower recurrence rate than a change in medication (S-ICD, 40% vs. 27% and TV-ICD, 44% vs. 17%). After an invasive action no recurrence of IAS occurred in both groups. Invasive actions were more common in the S-ICD group (7/41, vs. 1/29). In the S-ICD group the most common action was a change in programming (17/41), mainly when the underlying mechanism of IAS was cardiac oversensing. In the TV-ICD group the most common action was a change in medication (12/29), mainly and only when the underlying mechanism of IAS was an SVT (Figure 2.).

Conclusion
The total number of IAS and total patients receiving IAS are not statistically different between the S-ICD group and the TV-ICD group. However, the underlying mechanism and action after IAS differ and are associated with the different sensing of the ICDs. The recurrence rate after a first IAS was significantly higher when no action was undertaken.