SMART Pass automatic deactivation of subcutaneous implantable cardioverter-defibrillators

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.

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

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.

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).

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.