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CLINICAL STUDY: ELECTROPHYSIOLOGY

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

^a Departments of Medicine and Physiology, Medical College of Virginia at Virginia Commonwealth University, Richmond, Virginia, USA
^b Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Richmond, Virginia, USA

Manuscript received March 29, 1999; revised manuscript received October 17, 2001, accepted December 20, 2001.

^* Reprint requests and correspondence: Dr. Dwain L. Eckberg, Hunter Holmes McGuire Department of Veterans Affairs Medical Center, 1201 Broad Rock Boulevard, Richmond, Virginia 23249, USA
deckberg{at}aol.com

OBJECTIVES: 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.

BACKGROUND: 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.

METHODS: 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]).

RESULTS: 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 any cerebral 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) before reductions of MAP. Cerebral and systemic hemodynamic measurements remained constant in nonsyncopal patients.

CONCLUSIONS: 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.

Abbreviations and Acronyms   ANOVA   ANOVA   analysis of variance   CBFV   cerebral blood flow velocity   MAP   mean arterial pressure

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