Neuropathic Postural Tachycardia Syndrome -- What's the Defect?

The neuropathic postural tachycardia syndrome (also known as idiopathic orthostatic intolerance) consists of orthostatic symptoms that occur upon standing, including lightheadedness, dimming of vision, and anxiety. It is associated with a substantial increase in heart rate but no decrease in blood pressure and primarily affects young women.

These researchers sought to elucidate the syndrome's pathophysiology by studying 10 patients and 8 age- and sex-matched controls. The experiments included measurements of venous catecholamines in the arms and legs, both at baseline and in response to various stimuli of the sympathetic nervous system. The results suggested low neuronal stores and impaired release of norepinephrine in the legs of patients w…