Ivabradine for inappropriate sinus tachycardia: another piece of evidence

This editorial refers to ‘Metoprolol succinate vs. ivabradine in the treatment of inappropriate sinus tachycardia in patients unresponsive to previous pharmacological therapy’ by P. Ptaszynski et al. , on page 116 Prevalence of inappropriate sinus tachycardia (IST) defined by heart rate criteria is estimated to be 1.2% in the middle-aged population.1 Its clinical presentation with polymorphic symptoms of variable intensity, sometimes including debilitating palpitations and general incapacity, is fortunately much less common.Pathophysiological background of this infrequent entity remains poorly understood and several investigations led to rather controversial results.2 Enhanced intrinsic automaticity of the sinus node and/or impairment of cardiac autonomic regulation were suggested. Inappropriate sinus tachycardia has also been linked to the presence of beta-receptor stimulating autoantibodies.3 The clinical features of IST significantly overlap with postural orthostatic tachycardia syndrome, so that extracardiac autonomic system abnormalities may play an important role. For all these reasons, a multidisciplinary model in managing IST patients was proposed.4Beta-blockers are the cornerstone of pharmacological therapy for IST that may be replaced by or combined with non-dihydropyridine calcium channel blockers. Since this therapy is ineffective or associated with intolerable side effects in approximately one-third of patients, radiofrequency catheter modification of sinus nodal region has been proposed. This approach should be reserved for highly symptomatic patients who are refractory to medical therapy because ablation has no clear acute endpoint and may be associated with significant complications. Also long-term outcomes were disappointing.4 Due to the ‘systemic’ nature of IST, invasive procedure may, however, identify a considerable proportion of associated non-IST arrhythmias that can be cured by radiofrequency ablation more successfully.5 …