The use of non‐linear analyses in the characterization of hypertension and associated autonomic dysfunction

Abstract

To assess the relative merits of linear vs non‐linear analysis methods for detecting early autonomic changes in prehypertensive (PHT) subjects, we compared 24hr ambulatory blood pressure (BP) recordings for 6 PHT and 6 matched normotensive (NT) subjects. Along with linear techniques (BP variability, heart rate variability and baroreflex using the alpha method), we used non‐linear techniques (approximate entropy, detrended fluctuation analysis and return map/Poincare plot). Analysis was blinded. RESULTS: While standard linear methods did not discriminate between PHT and NT, non‐linear techniques showed significant differences. Approximate entropy analysis of systolic BP data exhibited higher values throughout the 24hr period (p < 0.05). Detrended fluctuation analysis of the daytime BP revealed elevated alpha‐1 of systolic BP in the PHT subjects (p < 0.05). The return map/Poincare plot of the 2 groups failed to reveal any clearly statistically significant changes. In summary, non‐linear analysis tools appeared superior to linear analyses in detecting PHT from NT subjects, and should be considered when dealing with non stationary and difficult data sets. Support: VIDDA foundation.