A Novel Assessment of Baroreflex Activity Through the Similarity of Ternary Codes of Oscillations Between Arterial Blood Pressure and R–R Intervals

Abstract

Arterial baroreflex plays a crucial role in the homeostasis of blood pressure. Elevated blood pressure stimulates baroreceptors and slows the heart rate consequently. Baroreflex activity has been quantified as the relationship between systolic blood pressure (SBP) and ECG R–R intervals (RRI), which is called baroreflex sensitivity (BRS). The purpose of this study is to define a new parameter of BRS and verify the reproducibility and validity of this indicator as compared with a popular BRS estimated by sequence method and a traditional BRS evaluated by pharmacological intervention. At first, the spontaneous oscillations of SBP and RRI were defined by ternary arithmetic codes: decrease as 0, unchanged as 1 and increase as 2. The new BRS was quantified as the similarity between these two ternary coded series after decimalization with different digits from 3 to 5. The validity and reproducibility of this method were verified in vivo in 10 adult male Wistar Kyoto rats. This new parameter correlated well with the BRS estimated by the sequence method and pharmacological intervention. The reproducibility of this novel method was good according to the Bland–Altman plot. This study offered a simple and reliable algorithm to estimate BRS, which can be embed in current instruments for clinical research.