title: Metoprolol succinate vs. ivabradine in the treatment of inappropriate sinus tachycardia in patients unresponsive to previous pharmacological therapy.
abstract: OBJECTIVE
  Inappropriate sinus tachycardia (IST) is a clinical syndrome characterized by excessive resting heart rate (HR) or disproportional increasing HR during exercise. The treatment of IST symptoms using beta-blockers or calcium channel-blockers is often non-effective or not well tolerated. Ivabradine is a new agent inhibiting sinus node I(f) current, resulting in a decrease of HR without haemodynamic compromise.
  
  
  RESULTS
  We enrolled 20 patients (36 ± 10 years; 14 women) affected by IST and resistant to previous administered therapy by using beta-blockers or verapamil. After 4 weeks of treatment with metoprolol succinate (up to 190 mg once a day) the therapy was switched to ivabradine up to 7.5 mg twice daily. Holter monitoring and treadmill stress test were performed after 1 and 2 months following start of the study. We observed a significant reduction of resting HR both for metoprolol and for ivabradine compared with baseline (92.8 vs. 90.2 vs. 114.3 b.p.m.; P< 0.001). During daily activity there was an even larger decrease of HR on ivabradine (mean daytime HR 94.6 vs. 87.1 vs. 107.3 b.p.m.; P< 0.001). Ivabradine was very well tolerated whereas in 10 patients on metoprolol we observed hypotension or bradycardia requiring dose reduction. Significantly lower incidence of IST-related symptoms were registered on ivabradine therapy than on metoprolol. Fourteen patients (70%) treated with I(f) blocker were free of IST-related complaints.
  
  
  CONCLUSIONS
  Metoprolol and ivabradine exert a similar effect on resting HR in patients with IST. Ivabradine seems to be more effective to relieve symptoms during exercise or daily activity.
authors: Department of Electrocardiology, Medical University Lodz, Regional Sterling Heart Disease Center, Sterling 1/3, 91-425, Lodz, Poland. pawel_ptaszynski@wp.pl
authors: Pawel
authors: P
authors: Ptaszynski
authors: Krzysztof
authors: K
authors: Kaczmarek
authors: Jan
authors: J
authors: Ruta
authors: Thomas
authors: T
authors: Klingenheben
authors: Jerzy K
authors: JK
authors: Wranicz
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000627:therapeutic use; D000328:Adult; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use; D001552:Benzazepines / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D000077550:Ivabradine; D008297:Male; D008790:Metoprolol / Q000031:analogs & derivatives* / Q000627:therapeutic use; D013616:Tachycardia, Sinus / Q000175:diagnosis* / Q000188:drug therapy*; D017211:Treatment Failure; D016896:Treatment Outcome
chemical_list: D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D001552:Benzazepines; D000077550:Ivabradine; D008790:Metoprolol