Baroreflex sensitivity and essential hypertension in adolescents

It has been known for many years that baroreflex sensitivity islowered in hypertensive patients. There are several knownfactors implicating this association, e.g. high blood pressure leadsto remodeling of the carotid arterial wall, to its stiffness and to adiminished activation of baroreceptors; leptin released from afatty tissue activates the sympathetic nervous system etc. On theother hand, low baroreflex sensitivity (BRS, usually quantified inms/mmHg) can be inborn. Studies on primary hypertension inchildren and adolescents have brought new information aboutthe role of baroreflex in the development of an early stage ofprimary hypertension. BRS lower than 3.9 ms/mmHg was foundin 5 % of healthy subjects. This value approaches the criticalvalue for the risk of sudden cardiac death in patients aftermyocardial infarction and corresponds to the value present inhypertensive patients. A decreased BRS and BRSf (baroreflexsensitivity expressed in mHz/mmHg, index independent of themean cardiac interval), was found not only in children withhypertension, but also in those with white-coat hypertension.This is in accordance with a single interpretation. The decrease ofBRS/BRSf precedes a pathological blood pressure increase. Thecontribution of obesity and BRS/BRSf to the development ofhypertension in adolescents was also compared. Both factorsreach a sensitivity and a specificity between 60 % and 65 %, butthere is no correlation between the values of the body massindex and BRS either in the group of hypertensive patients or inhealthy controls. If a receiver operating curve (sensitivity versusspecificity) is plotted for both values together using logisticregression analysis, a sensitivity higher than 70 % and aspecificity over 80 % are reached. This means that low baroreflexsensitivity is an independent risk factor for the development ofprimary hypertension. Studies demonstrate that adolescents withincreased blood pressure and with BRS under 7 ms/mmHg shouldbe given care and intensively motivated to change their lifestyleincluding a change in diet and increase in physical activity.