Abstract
BACKGROUND: β-Adrenoceptor antagonists (β-blockers) have been reported to be effective for regulation of heart rate (HR) and restoring sinus rhythm in postoperative atrial fibrillation and atrial flutter, as well as in the prevention of those arrhythmias after open-heart surgery. OBJECTIVES: The objectives of this study were to evaluate the dose-dependent effects of landiolol, an ultra-short-acting β1-blocker, as well as the effectiveness and safety of the drug in suppressing supraventricular tachyarrhythmias (SVT) in postoperative patients. METHODS: Landiolol was administered as a four-dose titration regimen (LL, L, M, and H doses) to postoperative patients who developed SVT. The titration sequence began with a 1-min loading infusion at a rate of 0.015 mg/kg/min, followed by a 10-min continuous infusion at 0.005 mg/kg/min (the LL dose). Infusions at progressively higher doses followed in sequence until 20 % reduction in HR was achieved. The L dose was a 1-min loading infusion at 0.03 mg/kg/min, followed by a 10-min continuous infusion at 0.01 mg/kg/min. The M dose was a 1-min loading infusion at 0.06 mg/kg/min, followed by a 10-min continuous infusion at 0.02 mg/kg/min. The H dose was a 1-min loading infusion at 0.125 mg/kg/min, followed by a 10-min continuous infusion at 0.04 mg/kg/min. The patient was then observed for 30 min to determine the cardiovascular responses to withdrawal of the medication. After completion of this follow-up period, additional maintenance infusion for up to 6 h was permitted if considered necessary by the investigator. RESULTS: A total of 108 patients were enrolled in this study. The cumulative improvement rates (percentage of patients obtaining ≥20 % reduction in HR) were 11.4, 32.4, 63.1, and 87.3 % at the LL, L, M, and H doses, respectively, demonstrating the dose-dependent effectiveness of landiolol. Additional infusion for up to 6 h was conducted in 16 patients. HR was maintained between 95.5 and 116.8 beats/min during the maintenance period (mean 259.8 min). Landiolol was generally well tolerated, although one patient with sick sinus syndrome developed an approximately 5-s cardiac arrest. CONCLUSIONS: The overall results, including those pertaining to patient safety, demonstrate that landiolol is effective and useful for the treatment of postoperative SVT.