Isometric Exercise, Cold Pressure Test, and Valsalva Maneuver in Subjects with Essential Hypertension and Normal Blood Pressure

Synpathetic overactivit)t has been considered to be one of the underlying causes of h5'pertension; however, the uanagenrent of hypertension u,ilh anti-q,upathetic drugs is often unsatisfactoôt. B! using autononùc reflex testing, i.e., isontetic exercise, cold pressor test, at'td Volsalva ,,nneu.ver, we invesligated the aufononic reJlet( patlerns before and afier lreatnent itl 8 (mean age 48, SE 2.7 ysa751 unconplicoted tnild to ,iloderate essenrial hypertensive patients. Six age-natched nonnotensive (nean age 40, SE 2 years) subiecîs served as a control group. Data collected in this study v,ere the percentages ofincreose of heart rale and blood pressure. Percentage increase of blood pressure during isouetric etercise and cold pressor test in the h1'pertension BrouP N,as le.ss than those in the control group. This attenuatio,l ,,n), be due to the already overactive $'npathelic nervous syslelt in the hypertensive group causing desensitization ôf baroreceptors, which nakesfurther increase of blood pressure dfficult. In phases II and III of Valsalva ilrcneuveL the percenrage increase in heart rale (s)'t,tpothetic activation) in the hypertensive groupwas less than that in the control group (p < 0.05); v,hile in phases I and IV of Valsalva t,raneuver, the h)'pertensive group also showed a significant less decrease (vagal activation) in heort rate compared u,ith rhe control group (p < 0.05). When blood pressure ofthe hypertettsive group had been reduced by diet or low dose thiazide, the dffirences in the percenlage increase of blood pressure'during isometric exercise and cold pressor test, and the perce,ltage increase in heart rate during phases II and III of the Valsalva naneuver between hypertensive group and control group were significanr. However, the less decrease ofheart rate in phases I and IV ofVaLsalva nrcneuver in hypertensive grouP was still unchanged Since there is avagal corûrol of sl,upathetic acrivit)', thisfinding suggested that iupairment of vagal contponent nq' be resPonsiblefor the developne,il of h)'pertension, secondarl'to increased s1'upalhetic adiviry. Keyworils: autononic reflet testing, essenlial h;pertensiotr.