Pulsatility index in internal carotid artery in relation to transdermal oestradiol and time since menopause

The protection afforded by postmenopausal oestrogen replacement against cardiovascular disease is not fully explained by changes in plasma lipoproteins. To investigate the effect of oestrogen on arterial tone, Doppler ultrasound was used to assess blood flow characteristics in the internal carotid arteries of 12 postmenopausal women. Patients were studied pretreatment and at weeks 4, 6, 9, and 22 of therapy with transdermal oestradiol 50 micrograms/day. The pulsatility index (PI), which is thought to represent impedance to blood flow distal to the point of sampling, was measured from the flow velocity waveform. 11 of the 12 patients were within 5 years of menopause; 1 was 8 years postmenopausal but had experienced bleeding 4 years after menopause. In the 11 women there was a highly significant correlation (r = 0.77) between time since menopause and baseline PI. A similar correlation (r = 0.74) was observed when the episode of postmenopausal bleeding was redefined as time of menopause in the twelfth patient. For all 12 patients, there was a significant negative correlation (r = -0.70) between change in PI during transdermal oestradiol therapy and mean of baseline plus week 22 PI value. For all correlations between changes in PI and time since menopause, the longer the time the greater the fall in PI. These results, and previous observations of a reduction in uterine artery PI with oestradiol treatment, suggest that oestrogen has a generalised effect on the arterial system.