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Orthostatic decrease in cardiac chaos during the head-up tilt test in patients with vasovagal syncope.

Masaru Suzuki1, Shingo Hori, Yutaka Tomita

  • 1Department of Emergency Medicine, School of Medicine, Keio University, Tokyo, Japan. suzuki@sc.itc.keio.ac.jp

Circulation Journal : Official Journal of the Japanese Circulation Society
|June 27, 2006
PubMed
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Nonlinear analysis of heart rate variability (HRV) reveals decreased cardiac chaos during tilt tests in vasovagal syncope (VVS) patients. This finding aids in identifying VVS, even with negative tilt test results.

Area of Science:

  • Cardiology
  • Neuroscience
  • Physiology

Background:

  • Autonomic dysfunction is implicated in vasovagal syncope (VVS)-related orthostatic intolerance.
  • Traditional spectral analysis of heart rate variability (HRV) has not identified this autonomic dysfunction.
  • Nonlinear HRV analysis is hypothesized to detect orthostatic intolerance in VVS.

Purpose of the Study:

  • To investigate if nonlinear analysis of HRV can identify orthostatic intolerance in VVS patients.
  • To determine if cardiac chaos during a head-up tilt test is specific to VVS.

Main Methods:

  • Twenty-six VVS patients and 14 controls underwent an 80-degree head-up tilt test.
  • Spectral analysis of HRV was performed.
  • The Lyapunov exponent (LE) was calculated to assess cardiac chaos, defined by a positive finite LE.

Related Experiment Videos

Main Results:

  • No differences in orthostatic HRV spectral analysis indices were found between VVS patients and controls.
  • VVS patients (both tilt-positive and tilt-negative) exhibited orthostatic decreases in cardiac chaos.
  • Control subjects did not show a decrease in cardiac chaos during orthostatic stress.
  • Cardiac chaos during tilt testing demonstrated high sensitivity (85.7%) and specificity (96.2%) for identifying VVS.

Conclusions:

  • A decrease in cardiac chaos during tilt testing is a specific indicator for VVS.
  • This finding is valid even in VVS patients who have a negative response to the tilt test.