DIASTOLIC PRESSURE UNDERESTIMATES AGE-RELATED HEMODYNAMIC IMPAIRMENT

It has been hypothesized that as large arteries become more rigid with age, the pattern of hypertension changes from diastolic to systolic. Thus, diastolic blood pressure (DBP) may lose its ability to reflect t he increase in vascular resistance with age. To assess this, we studie d the age-related changes in blood pressure pattern and its steady-sta te and pulsatile determinants. We performed an epidemiological analysi s based on a national survey of 10 462 subjects from Argentina. A hemo dynamic analysis (impedance cardiography) was then carried out in 636 consecutive hypertensive patients (age, 25 to 74 years). Whereas the r ate of increment in the prevalence of mild to moderate hypertension (M MH) reached a plateau after the sixth decade, isolated and borderline systolic forms of hypertension began a steep and sustained rise. Among patients with MMH, DBP remained stable from the third to the seventh decade, whereas SEP maintained a sustained increase. Despite similar D BP, the systemic vascular resistance index increased 47% (P<.01) and t he cardiac index decreased 27% (P<.01), whereas the ratio of stroke vo lume to pulse pressure, an index of arterial compliance, decreased 45% (P<.01). However, there were no significant differences be tween olde r patients with MMH and those with isolated systolic hypertension in t he level of SEP, vascular resistance, stroke volume, and cardiac index . Compared with age-matched normotensive control subjects, the ratio o f stroke volume to pulse pressure was much more reduced in isolated sy stolic hypertension (48%) than in MMH (30%). In summary, the present s tudy, carried out in a large sample of hypertensive subjects with a wi de age range, showed a simultaneous impairment in vascular resistance and arterial compliance associated with aging in different patterns of hypertension. The magnitude of these changes, with opposite effects o n DBP but additive effects on SEP, suggests that a hemodynamic mechani sm could determine the transition in the prevalence of diastolic hyper tension toward a systolic pattern of hypertension with aging. Also, th e results suggest that SEP, but not DBP, is a reliable indicator of th e underlying hemodynamic abnormalities (high resistance and low arteri al compliance) in the elderly.