The Orthostatic Tachycardia Syndrome: Evaluation of Autonomic Function and Treatment with Octreotide and Ergot Alkaloids*

Orthostatic tachycardia is a poorly understood syndrome in which patients develop dizziness, diaphoresis, or palpitations upon shifting from the supine to the upright posture. The present study was performed to determine whether autonomic neuropathy might be present in these patients, and whether the abnormal hemodynamic response to standing might be the result of failure of reflex vasoconstriction. We measured autonomic function in 9 patients with idiopathic orthostatic tachycardia and 2 patients with orthostatic tachycardia and insulin-dependent diabetes mellitus and compared them to 33 age-matched controls. Although most patients with orthostatic tachycardia had normal vasomotor reflexes and normal surface potential amplitudes, the latency of the autonomic response, a measure of sympathetic nerve conduction velocity, was prolonged in the soles (2.44 ± 0.08 s in patients with idiopathic orthostatic tachycardia vs. 2.12 ± 0.04 s in controls; P < 0.005). In 6 of 9 patients, however, the latencies were wit...