Diagnosis and Treatment of Inappropriate Sinus Tachycardia

Abstract

Inappropriate sinus tachycardia (IST) is a syndrome of cardiac and extracardiac symptoms characterized by rapid sinus heart rate at rest (>100 bpm) or with minimal activity and disproportionate to the physiologic demands. Patients with this unique and puzzling arrhythmia may require restriction from physical activity. The responsible mechanisms for IST are not completely understood. IST and postural orthostatic tachycardia syndrome (POTS) are the 2 sides of the same coin. It is important to distinguish IST from so-called appropriate sinus tachycardia and from POTS, with which an overlap may occur. As the long-term outcome seems to be benign, treatment may be unnecessary, or may be as simple as physical training. However, for patients with intolerable symptoms, therapeutic measures are warranted. Beta-adrenergic blockers, considered a first-line therapy, are usually ineffective even at high doses; the same applies for most other medical therapies. Ivabradine seems to be more effective than beta-blockers especially in the non- hypertensive patients. In rare instances, catheter- or surgically- based right atrial or sinus node modification may be helpful, but even this is fraught with limited efficacy and potential complications. Overtreatment, in an attempt to reduce symptoms, can be difficult to avoid, but is discouraged. In this report, we will be review IST, explore its mechanisms and evaluate possible management strategies.