Shock Reduction Programming Strategies

*PR Logic does not apply to the VR device(s)

Discrimination Algorithms – SmartShock™ 2.0 Technology

SmartShock 2.0 Technology reduces the incidence of inappropriate shocks while maintaining sensitivity to true VT/VF.1 SmartShock 2.0 Technology includes 6 exclusive algorithms that discriminate true lethal arrhythmias from other arrhythmic (SVTs and NSVTs) and nonarrhythmic events (oversensing, noise).


ATP Before Charging™ and ATP During Charging™

The ATP Before Charging and ATP During Charging features provide Antitachycardia Pacing (ATP) in response to a VT or FVT episode either before or while the device charges to deliver a shock. ATP consists of rapid sequences of pacing pulses to terminate detected ventricular tachyarrhythmias.

The EnTrust trial studied the ATP During Charging feature. This feature was developed to deliver ATP for rapid VT while charging for a shock, thereby decreasing the time to shock delivery following failed ATP. The evidence showed that the safety and efficacy of ATP delivered during charging was similar to that seen in prior trials.4 

Furthermore, there was no difference in the time to first shock delivery with ATP during charging turned on versus no ATP therapy. Based on these findings, ATP During Charging is nominally programmed On in all current Medtronic ICDs.

Succesful ATP During Charging operation



Programming VF Numbers of Intervals to Detection (VFNID) to 30 out of 40 intervals

The PREPARE study demonstrated that in primary prevention patients, a delayed detection is safe and effective and resulted in a 63% reduction in shocks. It also showed that a delayed detection was not associated with an increased risk of arrhythmia syncope or mortality.5 The RELEVANT and ADVANCE III trials showed that extending VF detection to 30 out of 40 intervals reduces ICD therapies without increasing the risk of syncope or mortality in single, dual, and CRT ICDs, ischemic and non-ischemic, and primary and secondary prevention patients.6,7 

The ADVANCE III trial demonstrated that programming a long detection (30 out of 40 intervals) reduced ICD therapies (ATP-during-charging and shocks) by 37%, although individual statistical significance was reached for ATP-during-charging only.7 (IRR = 0.63, RR = 1-0.63 = .37)

A sub-analysis of single chamber ICD patients programmed to long detection settings as compared to standard detection (18 out of 24 intervals), found a 48% reduction in overall therapy (ATP and shocks), a 40% reduction in shocks, and a 51% reduction in appropriate shocks.8 There was no difference in syncope between the long detection or standard detection (18 out of 24) groups, but survival improved in the long detection group.8

The PainFree SST trial had VFNID set to 30 out of 40 intervals for primary prevention patients and set to either 30 out of 40 or 18 out of 24 intervals for secondary prevention patients.1 More recent device models have VFNID nominally set to 30 out of 40 intervals to detect.


1 Auricchio A, Schloss EJ, Kurita T, et al. Low inappropriate shock rates in patients with single and dual/triple chamber ICDs using a novel suite of detection algorithms: PainFree SST Trial Primary Results. Heart Rhythm. 2015;12:926-36.
2 Protecta Clinical Study, Medtronic data on file
3 Evera™ XT DR/VR Manual
4 Schoels W, Steinhaus D, Johnson  et al. Optimizing implantable cardioverter-defibrillator treatment of rapid ventricular tachycardia: antitachycardia pacing therapy during charging. Heart Rhythm 2007;4:879–885.
Wilkoff B, Williamson BD, Stern RS, et al. Strategic programming of detection and therapy parameters in implantable cardioverter-defibrillators reduces shocks in primary prevention patients: results from the PREPARE (Primary Prevention Parameters Evaluation) study. J Am Coll Cardiol 2008;52:541–550.
Gasparini M, Menozzi C, Proclemer A, et al. A simplified biventricular defibrillator with fixed long detection intervals reduces implantable cardioverter defibrillator (ICD) interventions and heart failure hospitalizations in patients with non-ischaemic cardiomyopathy implanted for primary prevention: the RELEVANT [Role of long dEtection window programming in patients with LEft VentriculAr dysfunction, Non-ischemic eTiology in primary prevention treated with a biventricular ICD] study. European Heart Journal 2009;30:2758–2767.
7 Gasparini M, Proclemer A, Klersy C, et al. Effect of long-detection interval vs standard-detection interval for implantable cardioverter-defibrillators on antitachycardia pacing and shock delivery: the ADVANCE III randomized clinical trial. JAMA 2013;309:1903-1911.
8 Gasparini M, Lunati MG, Proclemer A, et al. Long detection programming in single chamber defibrillators reduces unnecessary therapies and mortality: the ADVANCE III trial. [published online May 11, 2017]. JACC Clin Electrophysiology, doi: 10.1016/j.jacep.2017.05.001.


Last updated: 
02 Jun 2017