VASCULAR DYNAMICS IN ISOLATED SYSTOLIC ARTERIAL-HYPERTENSION

With a growing elderly population, the incidence of isolated systolic hypertension (ISH) has increased. This study characterizes dynamic vas cular changes that occur with advanced age and with ISH. Fifty-five he althy individuals and seven with ISH were distributed in seven age gro ups from the second to the seventh decade. An index of aortic stiffnes s (Delta P/Delta V) was derived using a mercury sphygmomanometer to ob tain pulse pressure, and ultrasonographic measurements were used to es timate aortic volumes applying the ''cylinder formula.'' The mathemati c derivation of this formula is explained in detail. Pulse pressure sh owed no significant change with age, but showed a significant increase with ISH. A decrease in volume change from systole to diastole was fo und with advanced age. Normotensive subjects aged 65 +/- 2 years had a 2.6-fold increase in aortic stiffness compared with young individuals . Elderly patients with ISH had a 7-fold increase in aortic stiffness compared with Group 1 (15 +/- 2 years) (p < 0.001) and a 2.7-fold incr ease compared with Group 6 (normotensive subjects aged 65 + 2 years). A strong correlation between systolic pressure and arterial stiffness was observed (r = 0.953) (p < 0.001). The proposed stiffness index was compared with the one described by Hirai, obtaining a high correlatio n, that is, r = 0.989 (p < 0.001). When compared with Stefanadis's ind ex of distensibility, our index showed a correlation of r = 0.932 (p < 0.003). It is concluded that while systolic pressure is a main determ inant of arterial stiffness, the Delta P/Delta V is a more sensitive m ethod to estimate dynamic changes in elastic arteries such as the aort a.