Comparison of baroreflex sensitivity indices with standard tests of autonomic nervous system function

Objective: In order to further evaluate clinical usefulness of alpha- and 13-adrenergic components of the baroreflex sensitivity (BRS) index, the aim of this study was to compare them to standardized measures of the autonomic dysfunction. Methods: In 275 participants (mean age 40.57 +/- 15.19, range 18 to 89 years, 76.4% females) referred for testing of the autonomic nervous system, alpha-BRSa, 13-BRSa and BRSv were compared to heart rate (HR) and blood pressure (BP) values, adrenergic and cardiovagal indices of the Composite Autonomic Severity Score (CASS) and heart rate variability (HRV) parameters. Results: alpha-BRSa showed statistically significant positive correlation with HR in the supine position and negative with the adrenergic index. 13-BRSa showed statistically significant negative correlation with tests for parasympathetic nervous system function. BRSv showed statistically significant negative correlation with all HR and BP parameters and positive with all HRV parameters. In a univariable logistic regression analysis, alpha-BRSa was a negative predictor (Exp(B) 0.866, 95% CI 0.782-0.959, p = 0.006, respectively) of the pathological adrenergic index. To differentiate between subjects with normal and pathological adrenergic index, the optimal cutoff for alpha-BRSa was found to be 6.741, which gave a sensitivity of 61.0% and a specificity of 56.0%. Conclusion: BRSa indices showed a good correlation with standard measures of ANS function. The most promising test was alpha-BRSa, which performed well as a alpha adrenergic receptors mediated sympathetic nervous system marker.

Automated summary

The study aimed to compare the clinical usefulness of alpha- and beta-adrenergic components of the baroreflex sensitivity index with standardized measures of autonomic dysfunction. Results showed that alpha-BRSa had positive correlation with heart rate in the supine position and negative correlation with the adrenergic index, while beta-BRSa had negative correlation with tests for parasympathetic nervous system function. BRSv showed negative correlation with heart rate and blood pressure parameters and positive correlation with heart rate variability parameters.