Transcranial Doppler Studies on Cerebral Autoregulation Suggest Prolonged Cerebral Vasoconstriction in a Subgroup of Patients with Orthostatic Intolerance

• Published in: Ultrasound in medicine & biology Vol. 37; no. 10; pp. 1554 - 1560
• Main Authors: Lin, Ya-Ju, Po, Helen L, Hsu, Hung-Yi, Chung, Chih-Ping, Sheng, Wen-Yung, Hu, Han-Hwa
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.10.2011; Elsevier
• Subjects: Adult; Autonomic Nervous System - physiopathology; Biological and medical sciences; Blood Flow Velocity - physiology; Blood pressure; Cardiovascular system; Case-Control Studies; Cerebral autoregulation; Female; Heart rate; Hemodynamics; Humans; Hypotension; Intolerance; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Middle Cerebral Artery - diagnostic imaging; Orthostatic intolerance; Postural Orthostatic Tachycardia Syndrome - diagnostic imaging; Postural Orthostatic Tachycardia Syndrome - physiopathology; Posture; Radiology; Statistics, Nonparametric; Tachycardia; Tilt table; Tilt-Table Test; Transcranial Doppler ultrasonography; Ultrasonic investigative techniques; Ultrasonography, Doppler, Transcranial; Ultrasound; Valsalva Maneuver; Vasoconstriction; Vasoconstriction - physiology; Transcranial Doppler ultrasonography; Valsalva maneuver; Cerebral autoregulation; Tilt table; Orthostatic intolerance; Sonography; Doppler ultrasound study; Human; Transcranial route; Central nervous system; Encephalon
• ISSN: 0301-5629; 1879-291X
• DOI: 10.1016/j.ultrasmedbio.2011.06.008

Abstract We studied the cerebral autoregulation in a subgroup of patients with orthostatic intolerance, who exhibited excessively decreased middle cerebral artery flow velocity (MCAFV) on transcranial Doppler sonography (TCD) during head-up tilt (HUT) test but without orthostatic hypotension or postural tachycardia. Twenty patients and 20 age- and sex-matched controls underwent Valsalva maneuver (VM) and HUT test with simultaneous monitoring of MCAFV by TCD and blood pressure, heart rate recordings. The pulsatility index (PI), cerebrovascular resistance (CVR) and autoregulatory indices were calculated. During HUT, patients had marked MCAFV reduction (−29.0 ± 5.25% vs. −8.01 ± 4.37%), paradoxically decreased PI (0.68 ± 0.17 vs. 0.96 ± 0.28) but increased CVR (45.7 ± 16.7% vs. 14.3 ± 12.6%). The MCAFV decreased similarly during early phase II of VM in both groups but did not recover to baseline in patients during late phase II, phase III and less overshoot in phase IV (−11 ± 16.7% vs. +2.2 ± 17.9 %; −15.4 ± 16.5% vs. −2.4 ± 17.8% and 16.7 ± 22.9% vs. 38.7 ± 26.5%, respectively). We concluded that in these patients, cerebrovascular vasoconstriction in response to physiologic stimulation was normal but relaxation during and after stimulation were impaired, indicating prolonged cerebral vasoconstriction.