Ivabradine Versus Beta-blockers in the Treatment of Inappropriate Sinus Tachycardia

Inclusion Criteria: * Inappropriate sinus tachycardia (HR \>100 bpm at rest ECG and/or medium Holter ECG HR \>90 bpm) * Age \> 18 years; Exclusion Criteria: * Secondary causes of sinus tachycardia; * Structural heart diseases, * Postural orthostatic tachycardia syndrome; * Sinus nodal reentrant tachycardia; * Contraindications to beta-blockers; * Administration of beta-blockers, non-di-hydropiridinic calcium channels antagonists, class I and III anti-arrhythmic drugs or digitalis at the time of enrollment; * Age \< 18 years; * Inability of giving informed consent;