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Identical pattern of cerebral hypoperfusion during different types of syncope

Journal of Human Hypertension volume 24, pages 458–466 (2010)Cite this article

Abstract

Syncope is caused by insufficient oxygen supply to the brain. There have been attempts to classify syncope on the basis of defects in the venous system, arterial system (that is impaired systemic vascular resistance) or a combination of the two (that is mixed). We examined the hypothesis that a comparable decrease in cerebral perfusion would be evident at pre-syncope irrespective of the category of dysfunction. Young healthy volunteers (N=37) participated. The protocol consisted of 15 min supine rest, followed by 60° head-up tilt and lower body suction in increments of −10 mm Hg for 5 min each until pre-syncope. Beat-to-beat blood pressure (BP) (Finometer or intra-arterial), cardiac output (Finometer), middle cerebral artery blood velocity (MCAv), end-tidal CO2 and cerebral oxygenation were monitored continuously. At pre-syncope, mixed dysfunction was common (21 out of 37 participants), followed by venular dysfunction (15 out of 37 participants). In the venular and mixed groups, comparable orthostatic tolerance and declines in BP (−37 vs −43% from baseline, respectively), end-tidal PCO2, MCAv (−35 vs −38%) and cerebral oxygenation (−5 vs −7%) were evident despite distinct mechanisms purportedly being responsible for the hypotension. Although different determinants of hypotension do exist, cerebral hypoperfusion occurs to a similar extent.

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Acknowledgements

Funding from the Department of Physiology.

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Authors and Affiliations

  1. Department of Physiology, University of Otago, Dunedin, New Zealand

    K N Thomas & C K Willie

  2. Department of Medical and Surgical Sciences, University of Otago, Dunedin, New Zealand

    S D Galvin & M J A Williams

  3. O'Brien Centre, Faculty of Medicine, University of Calgary, Calgary, Canada

    C K Willie

  4. Department of Human Kinetics, University of British Columbia Okanagan, Kelowna, Canada

    P N Ainslie

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Correspondence to P N Ainslie.

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Thomas, K., Galvin, S., Williams, M. et al. Identical pattern of cerebral hypoperfusion during different types of syncope. J Hum Hypertens 24, 458–466 (2010). https://doi.org/10.1038/jhh.2009.93

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