Validation Of A New S-ICD Algorithm To Reduce Oversensing Of Dynamic T-Waves In Patients With Brugada Syndrome

The subcutaneous implantable cardioverter-defibrillator (S-ICD) should be considered as an alternative to transvenous defibrillators in patients with an ICD indication when pacing therapy for bradycardia support, cardiac resynchronization or ventricular tachycardia management is not necessary.1 This class IIa recommendation from the 2015 ESC guidelines can often be applied to patients with inherited channelopathies, since these patients usually require decades of ICD therapy without developing a need for any type of pacing support. On the other hand, especially in patients with Brugada Syndrome (BrS), the dynamic nature of ECG morphology may increase the risk for cardiac T-wave oversensing (TWOS), which has also been reported the main cause of inappropriate shocks (IAS) in the general S-ICD population. In order to avoid unnecessary sensing issues with the S-ICD, baseline ECG screening is recommended prior to the implantation procedure. Recently, it has been shown that eligibility failure for S-ICD can occur in up to 13% of patients with an inherited primary arrhythmia syndrome and that patients with BrS present the highest rate of screening failure if compared with other channelopathies.

As of yet, this QRS and T-wave morphology assessment can be done with an algorithm-based automated screening tool (AST) that mimics the sensing set-up process of the S-ICD after implant.

Recently, a novel 9Hz high-pass filter (SMART Pass, available for all EMBLEM S-ICD models) has been introduced to reduce the risk of TWOS with the S-ICD12. This algorithm is only available with the S-ICD sensing mechanism and has not been incorporated in the automated screening software12. Retrospective modelling of inappropriate shock events recorded in the EFFORTLESS registry have shown a reduction in inappropriate shocks by ~80% with SMART Pass compared to the first generation sensing algorithm of the S-ICD13. This was achieved without affecting the detection and the time to therapy for true ventricular arrhythmias.

Prospective data are lacking about the effectiveness of SMART Pass to discriminate T-waves in patients with dynamic ECG morphologies. This may be of particular interest since the occurrence of ECG morphology disturbances is usually difficult to be predicted in individual patients. As such, these data will provide additional guidance to the mandatory screening process for all S-ICD candidates, in particular for those who have a known risk factor for dynamic ECG changes, like patients withBrS. The main objective of this study will be to assess the efficacy of S-ICD with SMART Pass to discriminate dynamic T-waves amplitudes and morphologies over time.