1a_It has been known for many years that baroreflex sensitivity is lowered in hypertensive patients. There are several known factors implicating this association, e.g. high blood pressure leads to remodeling of the carotid arterial wall, to its stiffness and to a diminished activation of baroreceptors; leptin released from a fatty tissue activates the sympathetic nervous system etc. On the other hand, low baroreflex sensitivity (BRS, usually quantified in ms/mmHg) can be inborn. Studies on primary hypertension in children and adolescents have brought new information about the role of baroreflex in the development of an early stage of primary hypertension. BRS lower than 3.9 ms/mmHg was found in 5 % of healthy subjects. This value approaches the critical value for the risk of sudden cardiac death in patients after myocardial infarction and corresponds to the value present in hypertensive patients. A decreased BRS and BRSf (baroreflex sensitivity expressed in mHz/mmHg, index independent of the mean cardiac interval), was found not only in children with hypertension, but also in those with white-coat hypertension. This is in accordance with a single interpretation. The decrease of BRS/BRSf precedes a pathological blood pressure increase., 2a_The contribution of obesity and BRS/BRSf to the development of hypertension in adolescents was also compared. Both factors reach a sensitivity and a specificity between 60 % and 65 %, but there is no correlation between the values of the body mass index and BRS either in the group of hypertensive patients or in healthy controls. If a receiver operating curve (sensitivity versus specificity) is plotted for both values together using logistic regression analysis, a sensitivity higher than 70 % and a specificity over 80 % are reached. This means that low baroreflex sensitivity is an independent risk factor for the development of primary hypertension. Studies demonstrate that adolescents with increased blood pressure and with BRS under 7 ms/mmHg should be given care and intensively motivated to change their lifestyle including a change in diet and increase in physical activity., and N. Honzíková, B. Fišer.
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