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Cardiovascular reflex responses in patients with unexplained syncope.

M M Wahbha1, C A Morley, Y M al-Shamma

  • 1Department of Cardiovascular Studies, University of Leeds, U.K.

Clinical Science (London, England : 1979)
|November 1, 1989
PubMed
Summary

Recurrent unexplained fainting may indicate abnormal cardiovascular reflex control. This study found that patients with postural hypotension showed impaired blood pressure regulation and reduced cardiac output during head-up tilt tests.

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Area of Science:

  • Cardiology
  • Physiology
  • Neurology

Background:

  • Recurrent syncopal attacks often lack an apparent cause.
  • Cardiovascular reflex control may be implicated in unexplained syncope.

Purpose of the Study:

  • To investigate abnormal cardiovascular reflex control in patients with recurrent syncopal attacks.
  • To assess blood pressure, heart rate, and cardiac output responses during head-up tilting.
  • To evaluate baroreceptor sensitivity through carotid stimulation.

Main Methods:

  • Non-invasive assessment of cardiovascular responses to head-up tilting in 67 patients.
  • Measurement of steady-state responses of blood pressure, heart rate, and cardiac output.
  • Carotid baroreceptor stimulation via neck suction to assess pulse interval response.

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Main Results:

  • Two patients experienced vasovagal attacks during tilting; five developed attacks during prolonged tilting.
  • Eighteen patients exhibited postural hypotension, characterized by significant blood pressure drops.
  • Postural hypotension patients demonstrated a larger fall in cardiac output and diminished pulse interval response to baroreceptor stimulation compared to controls.

Conclusions:

  • Abnormal cardiovascular reflex control, particularly impaired baroreceptor function, is evident in some patients with recurrent unexplained syncope.
  • Postural hypotension is a significant finding in this patient group, linked to reduced cardiac output regulation.
  • Further investigation into cardiovascular reflexes is warranted for patients with unexplained recurrent syncope.