Effect of salt intake on beat-to-beat blood pressure nonlinear dynamics and entropy in salt-sensitive versus salt-protected rats.
Blood pressure exhibits substantial short- and long-term variability (BPV). We assessed the hypothesis that the complexity of beat-to-beat BPV will be differentially altered in salt-sensitive hypertensive Dahl rats (SS) versus rats protected from salt-induced hypertension (SSBN13) maintained on high-salt versus low-salt diet. Beat-to-beat systolic and diastolic BP series from nine SS and six SSBN13 rats (http://www.physionet.org) were analyzed following 9 weeks on low salt and repeated after 2 weeks on high salt. BP complexity was quantified by detrended fluctuation analysis (DFA), short- and long-range scaling exponents (αS and αL), sample entropy (SampEn), and traditional standard deviation (SD) and coefficient of variation (CV(%)). Mean systolic and diastolic BP increased on high-salt diet (P < 0.01) particularly for SS rats. SD and CV(%) were similar across groups irrespective of diet. Salt-sensitive and -protected rats exhibited similar complexity indices on low-salt diet. On high salt, (1) SS rats showed increased scaling exponents or smoother, systolic (P = 0.007 [αL]) and diastolic (P = 0.008 [αL]) BP series; (2) salt-protected rats showed lower SampEn (less complex) systolic and diastolic BP (P = 0.046); and (3) compared to protected SSBN13 rats, SS showed higher αL for systolic (P = 0.01) and diastolic (P = 0.005) BP Hypertensive SS rats are more susceptible to high salt with a greater rise in mean BP and reduced complexity. Comparable mean pressures in sensitive and protective rats when on low-salt diet coupled with similar BPV dynamics suggest a protective role of low-salt intake in hypertensive rats. This effect likely reflects better coupling of biologic oscillators.
Hariri School of Nursing, American University of Beirut, Beirut, Lebanon.
Souha A
SA
Fares
Vascular Medicine Program and Department of Internal Medicine, American University of Beirut, Beirut, Lebanon.
Joseph R
JR
Habib
Department of Anesthesiology, University of Michigan, Ann Arbor, Michigan.
Milo C
MC
Engoren
Vascular Medicine Program and Department of Internal Medicine, American University of Beirut, Beirut, Lebanon.
Kamal F
KF
Badr
Vascular Medicine Program and Department of Internal Medicine, American University of Beirut, Beirut, Lebanon Outcomes Research Unit - Clinical Research Institute, American University of Beirut, Beirut, Lebanon rh106@aub.edu.lb.
Robert H
RH
Habib
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D001795:Blood Pressure Determination; D004039:Diet, Sodium-Restricted; D019277:Entropy; D008297:Male; D017711:Nonlinear Dynamics; D051381:Rats; D020303:Rats, Inbred Dahl; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage*
D017673:Sodium Chloride, Dietary
Beat‐to‐beat variability; complexity; detrended fluctuation analysis