Key result
SMART Pass consistently ON in S-ICDs is linked to fewer inappropriate shocks and lower mortality.
Why the study?
The impact of SMART Pass status and automatic disabling on inappropriate shocks, appropriate shocks, complications, and mortality in S-ICD patients needed evaluation.
Does the SMART Pass algorithm reduce inappropriate shocks in primary prevention patients with a Subcutaneous ICD?
Cohort (n=1,111)
Does the SMART Pass algorithm reduce inappropriate shocks in primary prevention patients with a Subcutaneous ICD?
Maintaining the SMART Pass algorithm consistently ON in S-ICD patients significantly reduces inappropriate shocks without compromising appropriate therapy for ventricular arrhythmias.
Answers are grounded in this paper and cite their sources.
May reduce inappropriate S-ICD shocks with consistent SMART Pass; hypothesis-generating and leaves open need for randomized primary-prevention trials.
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.
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Boersma et al. (2022) conducted a cohort in Primary prevention patients with ejection fraction ≤35% and no pacing requirement (n=1,111). SMART Pass (SP) algorithm status vs. SP OFF or automatically disabled was evaluated on Inappropriate shocks, appropriate shocks, complications, and mortality. In patients with a subcutaneous ICD, having the SMART Pass algorithm consistently ON was associated with significantly fewer inappropriate shocks and lower univariate mortality (p=0.044).
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