Cerebral blood flow velocity declines before arterial pressure in patients with orthostatic vasovagal presyncope

• Published in: Journal of the American College of Cardiology Vol. 39; no. 6; pp. 1039 - 1045
• Main Authors: Dan, Dan, Hoag, Jeffrey B, Ellenbogen, Kenneth A, Wood, Mark A, Eckberg, Dwain L, Gilligan, David M
• Format: Journal Article
• Language: English
• Published: Legacy CDMS Elsevier Inc 20-03-2002; Elsevier Science; Elsevier Limited
• Subjects: Aerospace Medicine; Biological and medical sciences; Blood Flow Velocity - drug effects; Blood Flow Velocity - physiology; Blood pressure; Blood Pressure - drug effects; Blood Pressure - physiology; Cardiology; Cerebral Arteries - physiopathology; Cerebrovascular Circulation - physiology; Fainting; Female; Headache. Facial pains. Syncopes. Epilepsia. Intracranial hypertension. Brain oedema. Cerebral palsy; Heart; Heart Conduction System - drug effects; Heart Conduction System - physiopathology; Humans; Hypotension, Orthostatic - complications; Hypotension, Orthostatic - drug therapy; Hypotension, Orthostatic - physiopathology; Isoproterenol - therapeutic use; Male; Medical sciences; Middle Aged; Nervous system (semeiology, syndromes); Neurology; Patients; Software; Space life sciences; Studies; Sympathomimetics - therapeutic use; Syncope, Vasovagal - complications; Syncope, Vasovagal - drug therapy; Syncope, Vasovagal - physiopathology; Time Factors; Ultrasonography, Doppler, Transcranial; Variance analysis; Vascular Resistance - drug effects; Veins & arteries; CBFV; ANOVA; MAP; Non-Nasa Center; Nasa Discipline Cardiopulmonary; Sonography; Doppler ultrasound study; Human; Regional blood flow; Nervous system diseases; Pathophysiology; Consciousness impairment; Middle cerebral artery; Cardiovascular disease; Exploration; Vasovagal syncope; Tilt table; Transcranial route; Regulation(control); Arterial hypotension; Diseases of the autonomic nervous system; Blood pressure; Orthostatism; Neurological disorder; Brain (vertebrata); NASA Discipline Cardiopulmonary; Non-NASA Center
• ISSN: 0735-1097; 1558-3597
• DOI: 10.1016/S0735-1097(02)01719-9

We studied hemodynamic changes leading to orthostatic vasovagal presyncope to determine whether changes of cerebral artery blood flow velocity precede or follow reductions of arterial pressure.
Some evidence suggests that disordered cerebral autoregulation contributes to the occurrence of orthostatic vasovagal syncope. We studied cerebral hemodynamics with transcranial Doppler recordings, and we closely examined the temporal sequence of changes of cerebral artery blood flow velocity and systemic arterial pressure in 15 patients who did or did not faint during passive 70° head-up tilt.
We recorded photoplethysmographic arterial pressure, RR intervals (electrocardiogram) and middle cerebral artery blood flow velocities (mean, total, mean/RR interval; Gosling’s pulsatility index; and cerebrovascular resistance [mean cerebral velocity/mean arterial pressure, MAP]).
Eight men developed presyncope, and six men and one woman did not. Presyncopal patients reported light-headedness, diaphoresis, or a sensation of fatigue 155 s (range: 25 to 414 s) before anycerebral or systemic hemodynamic change. Average cerebral blood flow velocity (CBFV) changes (defined by an iterative linear regression algorithm) began 67 s (range: 9 to 198 s) beforereductions of MAP. Cerebral and systemic hemodynamic measurements remained constant in nonsyncopal patients.
Presyncopal symptoms and CBFV changes precede arterial pressure reductions in patients with orthostatic vasovagal syncope. Therefore, changes of cerebrovascular regulation may contribute to the occurrence of vasovagal reactions.