B-PO02-069 THE IMPACT OF A NEW ALGORITHM TO REDUCE INAPPROPRIATE SHOCK RATES IN THE UNTOUCHED STUDY

Abstract

The Subcutaneous implantable cardioverter defibrillator (S-ICD) has been shown to be safe and effective for patients (pts) at risk of sudden cardiac death. However, early generations of this device had high inappropriate shock rates (IAS), particularly due to cardiac T wave over sensing. Newer devices have improved sensing & discrimination capabilities including SMART Pass (SP). To determine the impact of SP to reduce IAS without adversely impacting appropriate shocks, complications & mortality rates in the UNTOUCHED trial. Primary prevention pts with ejection fraction ≤35% without an indication for pacing were prospectively enrolled and implanted with S-ICDs and followed for up to 18 months in UNTOUCHED (n=1111). Study protocol required programming provided for discrimination algorithms to determine therapy delivery for rates ≥200 beats per minute (bpm) and ≤ 250 bpm. Multivariable proportional hazard analysis was performed to determine IAS predictors. Kaplan-Meier analyses were performed to evaluate IAS, appropriate shock, complication, and mortality rates for SP ON vs OFF. SP was activated (ON) at discharge in 71% of pts. SMART Pass ON was found to be an independent predictor of lower rate of IAS (hazard ratio 0.48, p=0.033). Overall IAS rates at 1 year were 2.2% and 5.3% for pts with SP ON vs OFF respectively. Inappropriate shocks due to cardiac oversensing were significantly lower with SP ON: 2.0% vs SP OFF: 4.5%, p=0.023, whereas IAS due to non-cardiac oversensing showed similar reductions in IAS with SP ON that did not reach statistical significance (1.0% vs 2.6%, p=0.09). SP programming did not change the appropriate shock rate (5.7 vs 5.8%, p=0.89), complications (6.9 vs 8.5%, p=.40), or mortality (4.7 vs 6.1%, p=0.35). Patients in the UNTOUCHED trial with SMART Pass programmed ON versus OFF experienced significantly fewer inappropriate shocks without reducing appropriate therapy for VT/VF or affecting safety. The IAS rate was lower than any previous large multicenter S-ICD trial.