Carotid vascular resistance in long-term estrogen users.
OBJECTIVE
To compare carotid vascular resistance in long-term estrogen users with that of age-matched nonusers.


METHODS
Pairwise comparisons between 18 long-term users of 17beta-estradiol (E2) implants (mean age 67.8 years, mean duration of treatment 18.8 years, range 5.8-33.9 years) and 18 age-matched (+/- 2 years) nonusers. We used color Doppler ultrasound to assess pulsatility index (PI) and resistance index (RI) in common, external, and internal carotid arteries.


RESULTS
Estrogen users compared with age-matched nonusers had significantly lower mean values for common carotid RI, -4%; -0.04 (95% confidence interval [CI] -0.07, -0.03, P =.036) and marginally significant for PI, -12%; -0.25 (95% CI -0.54, 0.04, P =.087). Differences in external and internal carotids were smaller and insignificant. Age was a determinant of internal carotid vascular resistance in estrogen users and nonusers. Increasing pairwise differences in external carotid vascular resistance with advancing age (r = 0.55; P =.02), with magnitudes of mean group differences indicate a modest but true effect of long-term estrogen therapy on vascular resistance in common carotids, less in external, and negligible in internal carotid arteries. The study had an 80% power to detect a 10% mean difference (0.08 units) in common carotid RI at the 5% level. The standard deviation was considerably lower for estimates of RI than for PI.


CONCLUSIONS
Long-term estrogen therapy was associated with minor reduction of vascular resistance in common carotid, less in external, and negligible in internal carotid arteries. Effects on carotid vascular resistance do not seem to be a major mechanism in the long-term protective effect of estrogen therapy on cardiovascular risk.
Department of Women's and Children's Health, Section of Obstetrics and Gynecology, University Hospital, Uppsala, Sweden. tord.naessen@kbh.uu.se
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Naessen
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Bakos
D000368:Aged; D002318:Cardiovascular Diseases / Q000517:prevention & control; D002339:Carotid Arteries / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000502:physiology*; D016022:Case-Control Studies; D004958:Estradiol / Q000097:blood / Q000494:pharmacology*; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D011673:Pulsatile Flow; D018615:Ultrasonography, Doppler, Color; D014655:Vascular Resistance
D004958:Estradiol