Spontaneous baroreflex sensitivity: sequence method at rest does not quantify causal interactions but rather determines the heart rate to blood pressure variability ratio

N Wessel,K Berg,A Gapelyuk,J F Kraemer,J Kurths

doi:10.1088/1361-6579/ab7edc

Abstract

Objective:In order to quantify spontaneous baroreflex sensitivity (BRS) many groups use the sequence method (SME). In this paper we test the hypothesis that SME is quantifying causal interactions of spontaneous BRS at rest rather than, alternatively, being solely dominated by heart rate variability (HRV) and/or systolic blood pressure variability (BPV).Approach:Therefore, we retrospectively analyzed 1828 beat-to-beat time series and their corresponding systolic blood pressure during resting conditions.Main results:We found a high correlation between short-term HRV and the SME of baroreflex sensitivity of r = 0.85 (p < 0.001). The correlation is even higher between SME and the root mean square ratio of HRV and BPV (r = 0.93, p < 0.001). Surrogate analyses revealed that SME is not able to quantify causal relationships between both signals, it cannot differentiate between random and baroreflex driven sequences, and rather determines the HRV-BPV variability ratio.Significance:We conclude that SME has a potentially large methodological bias in the characterization of the capacity of the arterial baroreflex during resting conditions.

Highlights

The baroreflex exerts a strong influence on the regulation of the cardiovascular system in order to sustain homeostasis
Main results: We found a high correlation between short-term heart rate variability (HRV) and the sequence method (SME) of baroreflex sensitivity of r = 0.85 (p < 0.001)
The correlation coefficients r between SME and further HRV and blood pressure variability (BPV) parameters are given in table 2

Summary

Introduction

The baroreflex exerts a strong influence on the regulation of the cardiovascular system in order to sustain homeostasis. Modelling and quantifying this reflex have a high importance to understand the current state of the cardiovascular system and its behavior. The spontaneous sensitivity of the arterial baroreflex (BRS) is commonly estimated with the sequence method (SME) (Bertinieri et al 1985, Rothlisberger et al 2003), that supposedly quantifies this reflex directly. Several previous attempts exist that try to tune parameters in the SME, they did not verify if their method determines a causal bivariate relationship (Laude et al 2009, Silva et al 2019). In this letter we test whether SME is able to quantify causal interactions between heart rate and blood pressure, and estimate spontaneous BRS. Three surrogate analyses were performed where any actual relationship between blood pressure and heart rate signal was non-existent by construction

Methods

Results

Conclusion