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This Article Full Text Full Text (PDF) All Versions of this Article: 297/2/H664    most recent 00138.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Google Scholar Articles by Ocon, A. J. Articles by Stewart, J. M. PubMed PubMed Citation Articles by Ocon, A. J. Articles by Stewart, J. M.

Decreased upright cerebral blood flow and cerebral autoregulation in normocapnic postural tachycardia syndrome

Departments of ¹Physiology, ²Pediatrics, and ³Medicine, The Center for Hypotension, New York Medical College, Valhalla, New York

Submitted 9 February 2009 ; accepted in final form 30 May 2009

Postural tachycardia syndrome (POTS), a chronic form of orthostatic intolerance, has signs and symptoms of lightheadedness, loss of vision, headache, fatigue, and neurocognitive deficits consistent with reductions in cerebrovascular perfusion. We hypothesized that young, normocapnic POTS patients exhibit abnormal cerebral autoregulation (CA) that results in decreased static and dynamic cerebral blood flow (CBF) autoregulation. All subjects had continuous recordings of mean arterial pressure (MAP) and CBF velocity (CBFV) using transcranial Doppler sonography in both the supine supine position and during a 70° head-up tilt. During tilt, POTS patients (n = 9) demonstrated a higher heart rate than controls (n = 7) (109 ± 6 vs. 80 ± 2 beats/min, P < 0.05), whereas controls demonstrated a higher MAP than POTS (87 ± 2 vs. 77 ± 3 mmHg, P < 0.05). Also during tilt, mean CBFV decreased 19.5 ± 2.6% in POTS patients versus 10.3 ± 2.0% in controls (P < 0.05). We then used a transfer function analysis of MAP and CFBV in the frequency domain to quantify these changes. The low-frequency (LF; 0.04–0.15 Hz) component of CBFV variability increased during tilt in POTS patients (supine: 3 ± 0.9 vs. tilt: 9 ± 2, P < 0.02). In POTS patients, there was an increase in LF and high-frequency coherence between MAP and CBFV, an increase in LF gain, and a lack of significant change in phase. Static CA may be less effective in POTS patients compared with controls, since immediately after tilt CBFV decreased more in POTS patients and was highly oscillatory and autoregulation did not restore CBFV to baseline values until the subjects became supine. Dynamic CA may be less effective in POTS patients because MAP and CBFV during tilt became almost perfectly synchronous. We conclude that dynamic and static autoregulation of CBF are less effective in POTS patients compared with control subjects during orthostatic challenge.

chronic orthostasis; coherence; transcranial Doppler

This article has been cited by other articles:

				A. J. Ocon, J. Kulesa, D. Clarke, I. Taneja, M. S. Medow, and J. M. Stewart Increased phase synchronization and decreased cerebral autoregulation during fainting in the young Am J Physiol Heart Circ Physiol, December 1, 2009; 297(6): H2084 - H2095. [Abstract] [Full Text] [PDF]