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The pathophysiologic mechanisms associated with hypotensive susceptibility.

Ashish Chaddha1, Martina Rafanelli2, Michele Brignole3

  • 1Division of Cardiovascular Medicine, School of Medicine and Public Health, University of Wisconsin, H4/534 Clinical Science Center, 600 Highland Avenue, Madison, WI, 53792-3248, USA.

Clinical Autonomic Research : Official Journal of the Clinical Autonomic Research Society
|June 22, 2016
PubMed
Summary

Baroreflex gain is similar in patients with vasovagal syncope (VVS) and positive tilt table tests (TTT). However, an age-dependent decrease in baroreflex gain and increased vasodepressor response prevalence were observed in older individuals.

Keywords:
Baroreflex gainBlood pressureTilt table testVasovagal syncope

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Area of Science:

  • Cardiology
  • Autonomic Nervous System Function

Background:

  • Vasovagal syncope (VVS) is a common cause of syncope.
  • The ISSUE-3 trial indicated that pacing did not benefit VVS patients with positive tilt table tests (TTT), even with asystole.
  • Hypotensive susceptibility, revealed by TTT, is a potential explanation for VVS.
  • Understanding the pathophysiologic mechanisms of hypotensive susceptibility is crucial for VVS management.

Purpose of the Study:

  • To investigate the pathophysiologic mechanisms underlying hypotensive susceptibility in VVS patients.
  • To analyze baroreflex gain (BRG) and hemodynamic responses during TTT in VVS patients.
  • To compare these parameters between patients with positive and negative TTT results.

Main Methods:

  • 366 VVS patients undergoing TTT were analyzed.
  • Baroreflex gain (BRG), blood pressure (BP), and heart rate (HR) responses were measured during the initial 20 minutes of TTT.
  • Patients were categorized into positive (n=275) and negative (n=91) TTT groups.

Main Results:

  • Mean BRG was comparable between positive and negative TTT groups (12.5 ± 6.3 vs. 12.4 ± 6.3 ms/mmHg, p=0.72).
  • A significant age-dependent decrease in BRG was observed (p < 0.001).
  • Older patients showed a higher prevalence of vasodepressor response (p < 0.001).
  • While BP was similar, HR was significantly lower in the tilt-positive VVS group during the first 20 minutes of TTT.

Conclusions:

  • Baroreflex gain is similar in VVS patients with positive and negative tilt table tests.
  • An age-related decline in BRG and an increased tendency towards vasodepressor responses in older individuals were identified.
  • The clinical implications of the blunted heart rate response in tilt-positive VVS require further investigation.