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 PARAD1 discrimination algorithm in a general population implanted for primary or secondary prevention.
METHODS ISIS-ICD (Inappropriate Shock Reduction wIth PARAD1Rhythm 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 PARAD1. 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.
RESULTSIn total, 1013 patients (80.7% male; age 67.1 6 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 PARAD1, 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 personyears) 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 PARAD1 discrimination algorithm alone ranged from 1.0 to 2.1 per 100 person-years in a general population implanted for primary or secondary prevention.