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.

Introduction

The implantable cardioverter-defibrillator (ICD) has been shown to reduce mortality and sudden cardiac death in high-risk cohorts.1, 2, 3 Despite the life-saving benefit of these devices, concern has been raised regarding the morbidity associated with therapy. One of the major goals of ICD therapy is the accurate detection of ventricular tachyarrhythmias while minimizing inappropriate therapy for atrial arrhythmias. The importance of such arrhythmia discrimination has increased recently with the observation that inappropriate shocks are associated with worse outcomes in ICD patients.4, 5, 6 Whether shocks are causally related to increased mortality is controversial, but there is a clear consensus that inappropriate therapy should be minimized. In this regard, there are a number of strategies to reduce inappropriate therapy including pharmacologic interventions,⁷ device programming,8, 9 and advanced discrimination algorithms.10, 11, 12, 13, 14 Although it seems intuitive that dual-chamber sensing would improve arrhythmia discrimination, the results of previous prospective studies have been generally disappointing.15, 16 Accordingly, morphology-based algorithms and the timing of atrial- and ventricular-sensing events are often used in devices to discriminate arrhythmias. Although the general strategy of rhythm discrimination is similar between manufacturers, the algorithms are proprietary with significant differences in design. Moreover, comparisons between algorithms in implanted devices have not been performed previously. Accordingly, the Rhythm ID Goes Head to Head Trial (RIGHT) was designed as a prospective, randomized study comparing the discrimination algorithms of selected pulse generators from 2 manufacturers to prevent inappropriate therapy.