Systolic blood pressure (SBP) changes control the cardiac interbeat intervals (IBI) duration via baroreflex. Conversely, SBP is influenced by IBI via non- baroreflex mechanisms. Both causal pathways (feedback - baroreflex and feedforward - non- baroreflex) form a closed loop of the SBP- IBI interaction. The aim of this study was to assess the age -related changes in the IBI - SBP interaction. We have non -invasively recorded resting beat -to- beat SBP and IBI in 335 healthy subjects of different age, ranging from 11 to 23 years. Using a linear autoregressive bivariate model we obtained gain (Gain SBP,IBI, used traditionally as baroreflex sensitivity) and coherence (CohSBP,IBI) of the SBP-IBI interaction and causal gain and coherence in baroreflex (Gain SBP → IBI , Coh SBP → IBI ) and coherence in non- baroreflex (CohIBI→SBP) directions separately. A non -linear approach was used for causal coupling indices evaluation (C SBP → IBI , C IBI → SBP ) quantifying the amount of information transferred between signals. We performed a correlation to age analysis of a ll measures. CohIBI→SBP and CIBI→SBP were higher than CohSBP→IBI and CSBP→IBI, respectively. Gain SBP,IBI increased and Coh SBP → IBI decreased with age. The coupling indices did not correlate with age. We conclude that the feedforward influence dominated at rest. The increase of Gain SBP,IBI with age was not found in the closed loop model. A decrease of Coh SBP → IBI could be related to a change in the cardiovascular control system complexity during maturation., J. Svačinová, M. Javorka, Z. Nováková, E. Závodná, B. Czippelová, N. Honzíková., and Obsahuje bibliografii
We studied the relationship between blood pressure (BP), body mass index (BMI, kg/m2) and baroreflex sensitivity (BRS, ms/mmHg) in adolescents. We examined 34 subjects aged 16.2±2.4 years who had repeatedly high causal BP (H) and 52 controls (C) aged 16.4±2.2 years. Forty-four C and 22 H were of normal weight (BMI between 19-23.9), and 8 C and 12 H were overweight (BMI between 24-30). Systolic BP was recorded beat-to-beat for 5 min (Finapres, controlled breathing 0.33 Hz). BRS was determined by the cross-spectral method. The predicting power of BMI and BRS for hypertension was evaluated by sensitivity, specificity, and receiver operating curve (ROC - plot of sensitivity versus specificity). H compared with C had lower BRS (p<0.01) and higher BMI (p<0.05). Multiple logistic regression analysis (p<0.001) revealed that a decreased BRS (p<0.05) and an increased BMI (p<0.01) were independently associated with an increased risk of hypertension. No correlation between BMI and BRS was found either in H or in C. Following optimal critical values by ROC, the sensitivity, specificity and area under ROC were determined for: BMI - 22.2 kg/m2, 61.8 %, 69.2 %, 66.0 %; BRS - 7.1 ms/mmHg, 67.7 %, 69.2 %, 70.0 %; BMI and BRS - 0.439 a.u., 73.5 %, 82.7 %, and 77.3 %. Decreased BRS and overweight were found to be independent risk factors for hypertension., K. Krontorádová, N. Honzíková, B. Fišer, Z. Nováková, E. Závodná, H. Hrstková, P. Honzík., and Obsahuje bibliografii a bibliografické odkazy