Baroreflex sensitivity and its implication in neurally mediated syncope in children

Neurally mediated syncope(NMS)refers to an entity of syncopal disorders that can be triggered by a psychological stimulus,standing for a long time,sudden position change from supine to upright,or a muggy environment.Vasovagal syncope(VVS),also known as acute orthostatic intolerance(OI),is the main form of NMS[1]and seriously affects the quality of life of children.However,the pathogenesis of NMS has not yet been fully clarified.The mechanisms underlying NMS are considered to involve autonomic regu-lation abnormalities,low blood volume,abnormal vascular function,etc.Baroreflex sensitivity(BRS)is the sensitivity of baroreceptor reflex regulation,which controls cardio-vascular autonomic function.Abnormal regulation of the baroreflex has been identified as a fundamental mechanism underlying NMS.Arterial BRS describes the effectiveness of baroreflex during an alteration in blood pressure(BP)and is determined by evaluating changes in heart rate(HR)in response to BP alterations.