Algorithm-based reduction of inappropriate defibrillator shock: Results of the Inappropriate Shock Reduction wIth PARAD+ Rhythm DiScrimination-Implantable Cardioverter Defibrillator Study

Heart Rhythm. 2019 Sep;16(9):1429-1435. doi: 10.1016/j.hrthm.2019.03.016. Epub 2019 Mar 22.


Background: Inappropriate shocks (IS) continue to have a major negative impact on patients implanted with defibrillators.

Objective: The purpose of this study was to assess IS reduction with the PARAD+ discrimination algorithm in a general population implanted for primary or secondary prevention.

Methods: ISIS-ICD (Inappropriate Shock Reduction wIth PARAD+ Rhythm DiScrimination-Implantable Cardioverter Defibrillator) was a 2-year international, interventional study in patients implanted with a dual implantable cardioverter-defibrillator (ICD) or triple-chamber defibrillator (cardiac resynchronization therapy-defibrillator [CRT-D]) featuring PARAD+. IS (shocks not delivered for ventricular tachycardia or fibrillation) were independently adjudicated. The primary endpoint was percentage of IS-free patients at 24 months. Primary and worst-case analyses of annual incidence rates of patients with ≥1 IS, overall and per defibrillator type, were conducted.

Results: In total, 1013 patients (80.7% male; age 67.1 ± 11.4 years; 68%/30%/2% primary/secondary/other indication) were enrolled and followed for a median of 552 days (interquartile range 354; 725). Of 993 analyzed patients programmed with PARAD+, 14 had ≥1 IS, corresponding to a percentage free from IS of 98.1% (95% confidence interval [CI] 96.8%- 98.9%). Annual incidence rates (per 100 person-years) of patients with IS were 1.0 (95% CI 0.59-1.69) and 2.1 (95% CI 1.46-3.02) in the primary and worst-case analyses, respectively. In ICD patients, rates were 1.2 (95% CI 0.68-2.23) and 2.3 (95% CI 1.47-3.53), and in CRT-D patients 0.59 (95% CI 0.19-1.83) and 1.8 (95% CI 0.93-3.44) per 100 person-years.

Conclusion: The annual rate of defibrillator patients with IS using the enhanced PARAD+ discrimination algorithm alone ranged from 1.0 to 2.1 per 100 person-years in a general population implanted for primary or secondary prevention.

Trial registration: NCT01410552.

Keywords: Defibrillation; Discrimination algorithm; Shock; Ventricular fibrillation; Ventricular tachyarrhythmia.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Defibrillators, Implantable / adverse effects*
  • Electric Countershock* / adverse effects
  • Electric Countershock* / instrumentation
  • Electric Countershock* / methods
  • Equipment Failure / statistics & numerical data*
  • Equipment Safety / methods
  • Equipment Safety / statistics & numerical data
  • Female
  • Healthcare Failure Mode and Effect Analysis / methods
  • Humans
  • Male
  • Middle Aged
  • Outcome Assessment, Health Care
  • Tachycardia, Ventricular / therapy*
  • Ventricular Fibrillation / prevention & control*

Associated data