Prospective comparison of discrimination algorithms to prevent inappropriate ICD therapy: primary results of the Rhythm ID Going Head to Head Trial.

BACKGROUND Inappropriate therapy for supraventricular arrhythmias remains a significant source of morbidity in implantable cardioverter-defibrillator (ICD) recipients. OBJECTIVE The Rhythm ID Goes Head to Head Trial (RIGHT) was designed to compare rhythm discrimination and inappropriate therapies among patients with ICDs from 2 manufacturers. METHODS Patients with standard ICD indications were randomized to receive a Guidant VITALITY 2 with Rhythm ID or selective Medtronic pulse generators using the Enhanced PR Logic or Wavelet discrimination algorithms. A single- or dual-chamber device was implanted based on clinical indications and programmed in 2 detection zones with detection enhancements enabled for rates between 150 and 200 bpm. Algorithm performance was compared between randomization groups, stratified by single or dual chamber, for the primary end point of first inappropriate therapy (shock or antitachycardia pacing) for supraventricular arrhythmias. RESULTS There were 1962 patients enrolled and followed for 18.3 ± 9.2 months, with no difference in all-cause mortality between groups. There were 3973 treated episodes where electrograms were available and adjudicated. The primary end point of inappropriate therapy occurred in 246 of 985 VITALITY 2 patients vs 187 of 977 specific Medtronic ICD patients (hazard ratio = 1.34; confidence interval = 1.11-1.62; P = .003). Differences in inappropriate therapy were confined to single-chamber ICDs. Inappropriate shocks were more frequent in VITALITY 2 ICDs (hazard ratio = 1.63; confidence interval = 1.29-2.06; P < .001), with most therapies and performance differences occurring at slower rhythms (rates < 175 bpm). CONCLUSION Rhythm discrimination performed better in the specific Medtronic than in VITALITY 2 ICDs evaluated, particularly for single-chamber devices. Inappropriate therapies, and differences in performance, may be reduced with the use of rate cutoff above 175 bpm.