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Quantitative Autonomic Testing
11:40

Quantitative Autonomic Testing

Published on: July 19, 2011

Evaluation of the autonomic function in patients with hypertrophic cardiomyopathy with and without syncope

Milena Frota Macatrão-Costa1, Edmundo Arteaga-Fernandez, Fábio Sandoli de Brito

  • 1Instituto do Coração, Hospital das Clínicas, FM, USP, São Paulo, SP, Brasil. milenamacatrao@cardiol.br

Arquivos Brasileiros De Cardiologia
|March 19, 2013
PubMed

Insights

Patients with hypertrophic cardiomyopathy and unexplained syncope show reduced parasympathetic activity. Autonomic function testing, including head-up tilt, has limited value in diagnosing syncope in this population.

Area of Science:

  • Cardiology
  • Autonomic Neuroscience
  • Medical Diagnostics

Background:

  • Hypertrophic cardiomyopathy (HCM) patients may experience syncope due to hemodynamic collapse, potentially linked to autonomic imbalance.
  • Understanding autonomic function is crucial for managing syncope in HCM.

Purpose of the Study:

  • To compare autonomic function in HCM patients with unexplained syncope (US) versus those without syncope.
  • To assess the utility of baroreflex sensitivity (BRS) and heart rate variability (HRV) in differentiating these groups.

Main Methods:

  • Autonomic function was evaluated in 37 HCM patients (16 with US, 21 without) using spontaneous and phenylephrine-induced BRS.
  • Heart rate variability (HRV) was analyzed in time and frequency domains during 24-hour Holter monitoring and head-up tilt (HUT) tests.

Main Results:

  • No significant differences in spontaneous or phenylephrine-induced BRS, or overall HRV (SDNN) were found between groups.
  • HCM patients with US exhibited significantly lower parasympathetic indicators (RMSSD, pNN50, and high-frequency HRV) compared to controls.
  • Head-up tilt (HUT) testing showed poor sensitivity and specificity for identifying the cause of syncope in this cohort.

Conclusions:

  • HCM patients with unexplained syncope demonstrate reduced parasympathetic tone, though its clinical significance requires further investigation.
  • Head-up tilt (HUT) testing is not a reliable diagnostic tool for evaluating syncope etiology in HCM patients due to low specificity.
Abstract

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