Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 54, Issue 1 M17-M24, Copyright © 1999 by The Gerontological Society of America
Effects of age and gender on cardiovascular responses to phenylephrine
MJ Turner, CM Mier, RJ Spina and AA Ehsani
Section of Applied Physiology, Washington University School of Medicine, St. Louis, Missouri, USA.
BACKGROUND: The age-associated impairment in left ventricular (LV) systolic
function appears to be mostly detectable during exercise or sympathetic
stimulation. We hypothesized that the decline in cardiac function could be
unmasked by an acute increase in afterload induced by phenylephrine. We
further sought to examine whether the deterioration in cardiac function is
influenced by gender. METHODS: We studied 17 young (20-31 years old) and 21
older healthy subjects (60-75 years old) who were given infusions of
incremental doses of phenylephrine following cardiac muscarinic receptor
blockade with atropine. Left ventricular systolic function was assessed
with 2-D echocardiography. RESULTS: The young subjects exhibited a
paradoxical increase in heart rate in response to alpha-adrenergic
stimulation, but the older subjects did not (p < .01). The increase in
systolic blood pressure in response to phenylephrine was influenced by age
and gender (i.e., greater in the younger men and older women), whereas the
increase in diastolic blood pressure was greater in the younger than the
older subjects of both sexes. The changes in LV end-diastolic diameter with
phenylephrine were unaffected by age or gender. The slope of the systolic
shortening-end systolic wall stress relationship was significantly steeper
in the older subjects, suggesting a decline in the contractile response to
an acute increase in afterload with aging. CONCLUSIONS: This study's
findings suggest that age can significantly influence the cardiovascular
responses to alpha-adrenergic stimulation and that phenylephrine, by
acutely increasing afterload, is effective in unmasking the age-associated
deterioration in left ventricular systolic function. Further, it appears
that the increase in systolic blood pressure in response to an
alpha-adrenergic challenge is significantly influenced not only by age but
also by gender.
