Carotid vascular resistance in long-term estrogen users

Objective: To compare cartoid vascular resistance in long- term estrogen us ers with that of age-matched nonusers. Methods: Pairwise comparisons between 18 long-term users of 17 beta -estrad iol (E2) implants (mean age 67.8 years, mean duration of treatment 18.8 yea rs, range 5.8-33.9 years) and 18 age-matched (+/- 2 years) nonusers. We use d color Doppler ultrasound to assess pulsatility index (PI) and resistance index (RI) in common, external, and internal cartoid arteries. Results: Estrogen users compared with age-matched non-users had significant ly lower mean values for common cartoid RI, -4%; -0.04 (95% confidence inte rval [Cl] -0.07, -0.03, P = .36) and marginally significant for PI, 12%; -0 ,25 (95% Cl -0.54, 0.04, P = .087). Difference in external and internal car toids were smaller and insignificant. Age was a determinant of internal car toid vascular resistance in estrogen users and nonusers. Increasing pairwis e differences in external cartoids vascular resistance with advancing age ( r = 0.55; P = .02), with magnitudes of mean group differences indicate a mo dest but true effect of long-term estrogen therapy on vascular resistance i n common cartoids, less in external, and negligible in internal cartoid art eries. The study had an 80% power to detect a 10% mean difference (0.08 uni ts) in common cartoid RI at the 5% level. The standard deviation was consid erably lower for estimates of RI than for PL. Conclusion: Long-term estrogen therapy was associated with minor reduction of vascular resistance in common cartoid, less in external, and negligible in internal cartoid arteries. Effects on cartoid vascular resistance do not seem to be a major mechanism in the long-term protective effect of estroge n therapy on cardiovascular. (C) 2001 by The American College of Obstetrici ans and Gynecologists.