Long-Term Outcomes of Ivabradine in Inappropriate Sinus Tachycardia Patients: Appropriate Efficacy or Inappropriate Patients

Background Inappropriate sinus tachycardia (IST) is characterized by persistent and disproportional elevation of heart rate (HR). Ivabradine has been successfully used in some patients. Methods Twenty-four patients (18 women, 41 +/- 13 year olds) were diagnosed with IST according to current guidelines criteria. Patients were treated with 5-7.5 mg of ivabradine twice a day. Twenty-four-hour Holter recordings and the SF-36 Health Survey were performed at 6 months to evaluate both HR control and clinical status. Results Holter recordings before and after 6 months on treatment showed a significant reduction in the average maximal HR of 155 +/- 18 beats/min versus 132 +/- 16 beats/min, mean HR of 97 +/- 6 beats/min versus 79 +/- 8 beats/min (mean daytime HR of 103 +/- 8 beats/min vs 84 +/- 10 beats/min) and minimal HR of 58 +/- 12 beats/min versus 48 +/- 7 beats/min (Wilcoxon analysis, P < 0.05). The SF-36 mean score showed a significant improvement on ivabradine treatment (57 +/- 23 vs 76 +/- 20), with a better physical and mental status scores (56 +/- 25 vs 74 +/- 22 and 58 +/- 24 vs 78 +/- 18, respectively) (Wilcoxon analysis, P < 0.001). Mean dose of ivabradine was 5.8 +/- 1.4 mg. No episodes of severe bradycardia or syncope were reported. After 1 year, patients were asked to stop treatment to reevaluate the situation. Twenty patients were on treatment and only 10 patients accepted to stop ivabradine. Only two patients (20%) remained on IST criteria. Conclusions IST patients treated with ivabradine showed both HR normalization and quality-of-life improvement maintained in the long-term follow-up. Stopping ivabradine after 1 year unexpectedly showed that HR remained in the normal limits in 80% of the patients.