Clinical efficacy of ivabradine in patients with inappropriate sinus tachycardia : a prospective, randomized, placebo-controlled, double-blind, crossover evaluation

Objectives The purpose of this study was to investigate the role of ivabradine in the treatment of symptomatic inappropriate sinus tachycardia using a double-blind, placebo-controlled, crossover design. Background Due to its If blocking properties, ivabradine can selectively attenuate the high discharge rate from sinus node cells, causing inappropriate sinus tachycardia. Methods Twenty-one patients were randomized to receive placebo (n 10) or ivabradine 5 mg twice daily (n 11) for 6 weeks. After a washout period, patients crossed over for an additional 6 weeks. Each patient underwent symptom evaluation and heart rate assessment at the start and finish of each phase. Results After taking ivabradine, patients reported elimination of 70% of symptoms (relative risk: 0.25; 95% CI: 0.18 to 0.34; p 0.001), with 47% of them experiencing complete elimination. These effects were associated with a significant reduction of heart rate at rest (from 88 11 beats/min to 76 11 beats/min, p 0.011), on standing (from 108 12 beats/min to 92 11 beats/min, p 0.0001), during 24 h (from 88 5 beats/min to 77 9 beats/min, p 0.001), and during effort (from 176 17 beats/min to 158 16 beats/min, p 0.001). Ivabradine administration was also associated with a significant increase in exercise performance. No cardiovascular side effects were observed in any patients while taking ivabradine. Conclusions In this cohort, ivabradine significantly improved symptoms associated with inappropriate sinus tachycardia and completely eliminated them in approximately half of the patients. These findings suggest that ivabradine may be an important agent for improving symptoms in patients with inappropriate sinus tachycardia.