Effects of volume loading and pressor agents in idiopathic orthostatic tachycardia

BACKGROUND: Idiopathic orthostatic tachycardia (IOT) is characterized by an increase in heart rate (HR) with standing of > or = 30 bpm that is associated with elevated catecholamine levels and orthostatic symptoms. A dynamic orthostatic hypovolemia and alpha1-adrenoreceptor hypersensitivity have...

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Published in:Circulation (New York, N.Y.) N.Y.), 1997-07, Vol.96 (2), p.575-580
Main Authors: Jacob, G., Shannon, J. R., Black, B., Biaggioni, I., Mosqueda-Garcia, R., Robertson, R. M., Robertson, D.
Format: Article
Language:English
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Summary:BACKGROUND: Idiopathic orthostatic tachycardia (IOT) is characterized by an increase in heart rate (HR) with standing of > or = 30 bpm that is associated with elevated catecholamine levels and orthostatic symptoms. A dynamic orthostatic hypovolemia and alpha1-adrenoreceptor hypersensitivity have been demonstrated in IOT patients. There is evidence of an autonomic neuropathy affecting the lower-extremity blood vessels. METHODS AND RESULTS: We studied the effects of placebo, the alpha1-adrenoreceptor agonist midodrine (5 to 10 mg), the alpha2-adrenoreceptor agonist clonidine (0.1 mg), and I.V. saline (1 L) in 13 patients with IOT. Supine and upright blood pressure (BP) and HR were measured before and at 1 and 2 hours after intervention. Midodrine decreased both supine and upright HR (all HR values are given as bpm) at 2 hours (from 78+/-2 supine to 108+/-5 upright before treatment and from 69+/-2 supine to 95+/-5 upright after treatment, P
ISSN:0009-7322
1524-4539
DOI:10.1161/01.cir.96.2.575