Journal
HEART RHYTHM
Volume 15, Issue 2, Pages 240-247Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.hrthm.2017.10.004
Keywords
Inappropriate sinus tachycardia; Ivabradine; Sinus tachycardia; Symptoms; Tachycardia
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BACKGROUND Inappropriate sinus tachycardia (IST) is debilitating despite available treatment. Off-label use of ivabradine for IST prompted this systematic analysis of existing data quality and sample size estimates for adequately powered studies. OBJECTIVE To determine clinical efficacy of ivabradine in IST from pooled prospective studies. METHODS Analysis included ivabradine studies for IST participants without structural heart disease and with follow-up of >= 2 weeks. Heart rate and symptom reduction with ivabradine were estimated based on results of subjective change in symptoms assessed by various data instruments used in each study. Studies were assessed for quality using validated checklists. Sample sizes were calculated based on the magnitude of symptom reduction encountered after treatment with ivabradine. RESULTS Nine studies met criteria, culminating in 145 patients pooled. Most patients were women (>= 70%). Studies were small and not adequately powered, and all reported a decrease in maximum or mean resting heart rate or both, with complete or considerable amelioration of symptoms with ivabradine. Most studies had moderate quality with excellent consistency of study quality and narrow limits of agreement between the quality checklists. Sample size estimates for adequately powered studies with various placebo effects and comparisons with beta-blockade are reported. CONCLUSIONS Ivabradine effectively reduces heart rate and symptoms in IST, but no study was adequately powered to account for the expected placebo effect on symptoms. A multicenter, randomized, placebo-controlled, active, comparative study with a beta-blocker is needed for confirmation. This is especially relevant given the ivabradine's potential teratogenic effect, as many IST patients are females of childbearing potential.
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