The impact of SMARTpass algorithm status on inappropriate shock rates in the UNTOUCHED Study

Abstract

Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Boston Scientific Corporation Background The current Subcutaneous ICD (S-ICD) model incorporates SMART Pass (SP) to improve sensing and discrimination capabilities to reduce inappropriate shocks (IAS). SP status is programmable but may also be disabled automatically in the setting of low amplitude signals or low heart rate in order to avoid under-sensing of VT/VF. Objective To evaluate SP impact on IAS, appropriate shocks (AS), complications and mortality in the UNTOUCHED S-ICD trial. Methods Primary prevention patients (pts, n=1111) with ejection fraction ≤35% and no pacing requirement were followed for up to 18 months. SP status during a study visit was programmed ON or OFF and status between visits was either consistently OFF, ON, or automatically disabled (DIS). The impact of SP status on pt outcomes was evaluated using Kaplan-Meier (K-M) analysis. Multivariable proportional hazard analysis identified predictors of IAS and SP disable events. Results Percent of pts with SP always ON, always OFF, ON with DIS, and OFF then ON with no DIS were 56, 16, 15, and 13%, respectively. At least one SP DIS occurred in 177 pts, but only 13% had 2 or more, mostly due to PVCs and low EGM amplitudes. Significant multivariable predictors of SP disable events are history of atrial fibrillation (hazard ratio (HR) 2.49, odds ratio (OR) (1.49-4.16); p=.0005), only one passing vector at S-ICD screening, (HR 1.85, OR (1.10-3.10; p=.0202) and lower left ventricular ejection fraction (HR 1.05, OR (1.01-1.08); p=.0074). K-M IAS rates were highest for pts experiencing DIS (fig 1) and lowest for SP ON. While neither AS (p=0.58) nor complication (p=0.58) rates varied significantly according to SP status, mortality was lower for pts with SP ON during any duration of time (p=0.044) by univariate analysis. Further analysis is planned to better understand the relationship between SP status and mortality. Conclusion Patients in the UNTOUCHED trial with SMART Pass (SP) consistently ON had significantly fewer inappropriate shocks, with no impact on appropriate therapy for VT/VF. Patients with history of atrial fibrillation, lower left ventricular ejection fraction, and only one passing vector at S-ICD screening are at higher risk of SP disable events; therefore, care should be taken for these patients to assess SP status and their higher risk for inappropriate shocks.

Exploiting SMART pass filter deactivation detection to minimize inappropriate subcutaneous implantable cardioverter defibrillator therapies: a real-world single-centre experience and management guide

“… 6-11 Indeed, in the UNTOUCHED study where SP was enabled, SP reduced IT to 3.1% over 1 year predominantly through reduction in T wave oversensing (TWOS). 12 However, a key under-investigated feature is the algorithm’s ability to automatically deactivate itself, and the device is unable to reactivate this setting without in-clinic device interrogation. We aimed to assess: (i) the clinical factors associated with SP deactivation; (ii) why the device deactivates SP; and (iii) how to manage this scenario in a large, single-centre study.…”