Recurrent syncope triggered by inappropriate sinus tachycardia.

A 25-year-old woman with daily episodes of syncope and several related traumatic injuries was referred for electrophysiological study. Structural heart disease was excluded. Electrophysiological study revealed inappropriate sinus tachycardia with heart rates up to 190 beats/min. A sinus node modulation was performed. However, 5 days later the patient again developed syncope during sinus tachycardia at rates of 140 beats/min with systolic blood pressure of 60 mmHg. The patient subsequently underwent AVN ablation and implantation of a dual chamber pacemaker. The patient has remained asymptomatic during a 12-month follow-up. This article reports on the first case of a moderate sinus tachycardia in a structurally normal heart as an underlying mechanism of recurrent episodes of syncope. While moderate supraventricular tachycardia in a structurally normal heart alone is unlikely to explain the severe symptoms, additional sympathovagal or humoral mechanisms induced by sinus tachycardia may contribute to syncopal events in this patient.