Safety and feasibility of a novel rate-smoothed ventricular pacing algorithm for atrial fibrillation

Objectives This study was conducted to establish the safety and performance of a new rate-smoothing pacing algorithm for patients with atrial fibrilla tion (AF). Background Irregularity of the ventricular response is a hallmark of AF. Th is irregularity may contribute to symptoms and hemodynamic compromise in pa tients with AF. Interventions designed to reduce irregularity have not prev iously been evaluated in a long-term, clinical setting. Methods We designed a prospective, double-blind study with randomized cross over. Patients with either paroxysmal or chronic AF whose conditions were m edically refractory and who were referred for an atrioventricular node abla tion procedure all underwent pacemaker implantation. Subjects were then ran domly assigned to either DDD mode with the rate-smoothing algorithm (RSA) o n, or to OOO mode. After 2 months they were crossed over to the other arm. Results Fourteen patients (9 with paroxysmal AF and 5 with chronic AF) were enrolled. There were no significant differences between the group randomly assigned to RSA first versus the group assigned to OOO first. The mean lef t ventricular ejection fraction with the RSA was not significantly differen t than it was in OOO mode (45.1 +/- 18.6 vs 51.9 +/- 12.3; P = .11), althou gh some individuals with uncontrolled ventricular rates did have a large de crease in ejection fraction with rate smoothing. One developed overt heart failure. One quality-of-life instrument detected a significant improvement in the "physical limitations" domain with the rate-smoothing mode. Eleven o f 14 patients preferred the RSA ON arm, and 6 of those 11 elected to defer the ablation procedure. Conclusions Long-term rate-smoothed pacing is feasible. Because of concerns about pacing-induced heart failure in some patients with rapid ventricular rates, rate-smoothed pacing should be reserved for those who remain sympto matic despite adequate control of the ventricular rate. The RSA may help to reduce symptoms in patients with medically refractory AF; more study is re quired to define its efficacy in reducing symptoms and morbidity in this po pulation.