Inappropriate Sinus Tachycardia: Etiology, Pathophysiology, and Management

Inappropriate sinus tachycardia (IST) is a clinical syndrome that generally affects young patients and is associated with distressing symptoms. Although the most common symptom is palpitations, it can be accompanied by a myriad of symptoms, including anxiety, dizziness, presyncope, and syncope. The pathogenesis of IST is not well understood and considered multifactorial, with autonomic dysfunction being the central abnormality. IST is a diagnosis of exclusion. Management presents a clinical challenge. The overall efficacy of lifestyle modifications and medical therapy may be limited. Recent advances in catheter and surgical sinus node sparing ablation techniques have led to improvement in outcomes. In addition, increased focus has led to development of multimodality team-based interventions to improve outcomes in this group of patients. In this review, we discuss the mechanistic basis of IST, review current approaches to diagnosis, and outline contemporary therapeutic approaches. • IST is a diagnosis of exclusion defined by otherwise unexplained persistent or paroxysmal sinus tachycardia, resting heart rate >100 beats/min, and distressing symptoms. • Beta-blockers and calcium-channel blockers have limited efficacy, whereas ivabradine has shown promise in recent trials. • Catheter-based ablation has limited efficacy for treatment of IST, often requiring repeated procedures, but hybrid approaches based on SN modification provide better heart rate control.