SMART Pass automatic deactivation of subcutaneous implantable cardioverter-defibrillators

Background: The SMART Pass algorithm for subcutaneous implantable cardioverter-defibrillator prevents inappropriate shocks due to oversensing. The mechanisms and significance of SMART Pass deactivation remain unclear.

Objective: The objective of this study was to assess whether SMART Pass deactivation is associated with inappropriate shocks and to elucidate the underlying mechanism.

Methods: We retrospectively investigated 115 patients who underwent subcutaneous implantable cardioverter-defibrillator implantation between 2016 and 2021. SMART Pass deactivation and inappropriate shocks during follow-up were assessed. The QRS amplitudes of the subcutaneous (S-ECG) and 12-lead electrocardiogram (ECG) at the time of implantation (pre) and SMART Pass deactivation (post) were measured. The patients were divided into the SP-ON group with SMART Pass consistently on and the SP-OFF group with the experience of SMART Pass deactivation.

Results: Three of 12 patients in the SP-OFF group experienced inappropriate shocks during a median follow-up of 1094 (interquartile range, 887-1502) days compared with 4 of 87 patients in the SP-ON group. Pre- and post-S-ECG QRS amplitudes were significantly lower in the SP-OFF group than in the SP-ON group (both P < .05), despite similar 12-lead ECG QRS amplitude in both groups. A significant temporary drop in the QRS amplitude of the S-ECG led to SMART Pass deactivation (pre-QRS amplitude vs amplitude at deactivation, P = .015; 95% CI, 0.3-1.9).

Conclusion: The rate of inappropriate shocks was numerically higher after SMART Pass deactivation. A low QRS amplitude in S-ECG was a potential risk factor for SMART Pass deactivation. Careful follow-up and suitable management are required for managing patients with risks of SMART Pass deactivation.