The S-ICD sensing algorithm is challenged by drug-induced electrocardiographic abnormalities in patients with brugada syndrome: Results from a prospective multicenter study

Introduction: Up to 18% of patients with Brugada syndrome (BrS) fails the pre-implant screening for subcutaneous implantable cardioverter- defibrillators (S-ICD). It is still unknown if the S-ICD sensing algorithm (SMART Pass filter, SP) can reduce the screening failure due to cardiac oversensing; ajmaline challenge is emerging as a valuable tool to unmask S-ICD screening failure in BrS patients without spontaneous BrS Type 1 ECG pattern. Therefore, we conducted this study to assess the ability of the SP filter to discriminate QRS and T-waves after ajmaline administration and to reduce the S-ICD screening failure. Methods: S-ICD automated screening was performed in patients with suspected BrS, undergoing ajmaline challenge. ECGs of three sensing vectors were collected before, during and after ajmaline administration, in different postures and locations of the electrodes (left and right parasternal). Screen-out rate without the SP was determined by the automated screening tool (AST) and screen-out rate with SP filter was estimated using a simulation model. Results: Of 126 patients enrolled in the study, 46 (36%, mean age 45.5±12 years, males 79%) tested positive for BrS. In patients with drug induced BrS, 2505 sensing vectors were recorded for the analysis. AST failure rate after ajmaline administration was 20%, and decreased to 18% when SP filter was applied, whereas, vectors' failure rate decreased from 40% to 36%. The most frequent reason for screening failure was low amplitude of QRS and/or low QRS/Twave ratio. In BrS patients, right parasternal leads position did not significantly reduce vectors' screen-out rate (21% right parasternal vs. 22% left parasternal). At multivariable analyses, there were no differences in screen failure rates over the test phases depending on the use of filter (2-way interaction p=0.521 (vector) and p=0.052 (patient)). Conclusions: The SP filter does not significantly improve the overall S-ICD screen-out rate in patients with drug induced BrS. (Figure Presented).