Abstract 2514: Ivabradine is an Effective and Safe Treatment for Inappropriate Sinus Tachycardia
Introduction Inappropriate sinus tachycardia (IST) is characterized by an exaggerated increase in heart rate with sinual P wave, in the absence of predisposing conditions. Beta blockers, calcium channel blockers and anti-arrhythmic drugs are usually adopted to relief symptoms but are often poorly tolerated due to common side effects.
Hypothesis The purpose of this study was to evaluate the efficacy and safety of Ivabradine, a selective inhibitor of the If current present in the sino-atrial node, in IST treatment.
Methods We enrolled 9 pts (38±12 y, 8 female) affected by IST. Five mg Ivabradine were administered, up to 7,5 mg twice per day titrated to heart rate normalization. Prior to Ivabradine administration, one-, two-, and three months after, clinical visits and ECGs were performed, and patients were asked for symptoms and side effects. Exercise-ECGs and 24 hour-Holter ECGs were performed both prior to Ivabradine administration and three months after. Average heart rate, maximal and minimal heart rate, nocturnal and daytime average heart rate were assessed by Holter-ECG monitoring. Maximal heart rate, and maximal work step reached were assessed by ECG-stress test.
Results All patients experienced palpitations, fatigue and stress intolerance relief after Ivabradina assumption. One patient suffered phosphenes, which completely resolved in few days after drug assumption interruption. None of the other patients experienced further side effects. After three months, medium average, maximal and minimal heart rate at Holter-ECG reduced by 25%, 19% and 25% respectively; medium nocturnal- and daytime-heart rate also decreased by 23% and 29% respectively. Medium maximal heart rate reached during bicycle-ECG-stress test reduced by 15%, and medium maximal stress step reached increased by 25 watt after three months.
Conclusion Ivabradine seems to be effective in IST treatment, since it lowers heart rate and enhances exercise-stress tolerance. It is generally well-tolerated, with a few reversible side effects, thus representing an effective and safe alternative to calcium channel blockers and beta blockers in IST rate control.