Noninvasive hemodynamic assessment of the effect of mean arterial pressure on the amplitude of pulse pressure

Abstract

The present study compares the relationships between mean arterial pressure (MAP) and pulse pressure (PP) in young and older men and whether MAP determines age-related changes in PP. Impedance cardiography was used to evaluate systemic hemodynamics noninvasively in 189 unmedicated men referred to our hypertension unit. Patients were divided by age according to the median value (< and >/=40 years). In younger patients, increasing supine MAP was associated with a transition in the blood pressure pattern from systolic to diastolic, whereas in older patients, increasing MAP was associated with change from diastolic to systolic hypertension. In young patients elevation in MAP was associated with a parallel decrease in PP (P < .001) and stroke volume index (SVI) (P < .001), whereas in older patients higher MAP was associated with higher PP (P < .001) and PP/SVI ratio (P < .001), a measure of arterial stiffness. When the sample was divided according to the median value of MAP (< and >/=101 mm Hg), differences in the age-related change in PP and SVI became apparent. With a lower MAP, changes in PP and SVI remained parallel until the sixth decade, after which they began a progressive dissociation. In contrast, at higher MAP, the dissociation between PP and SVI began two decades earlier, indicating an acceleration of the age-related increase in arterial stiffness. Therefore, the relationship between MAP and PP was negative in younger men at the expense of a decrease in SVI, and positive in older men due to increasing arterial stiffness. Noninvasive hemodynamic parameters from impedance cardiography provide a useful method to characterize the mechanism of increased blood pressure.