Geometry of the carotid arteries and tilt-up hypotension in subjects with essential arterial hypertension.

Dysfunction of the baroreceptor structures located in the carotid bulb is considered responsible for hypotensive responses to orthostatic posture in hypertensive subjects. Because of a recurrent vascular impairment in essential hypertensives, the authors hypothesized that in these cases the baroreceptive dysfunction could be related to some peculiar vascular disarrangement of the carotid arteries, at the level of the bulb. To test this, they compared two groups of mild essential hypertensives, divided into group A--15 subjects considered hyporeacting because of a decrease in mean blood pressure > or = 10 mmHg at the first minute of a passive orthostatic stress--and group B--15 subjects considered normoreacting because of an increase in mean blood pressure > or = 5 mmHg. They evaluated by high definition echo Doppler ultrasonography: (1) an arterial compliance index, (2) the volume of the carotid bulb, and (3) a score expressing the degree of arteriopathy at the level of the carotid arteries. In group A, results demonstrated a significant impairment of the carotid artery structure, expressed by an increase in volume of the carotid bulb (389.4 +/- 134.7 vs 233.2 +/- 116.5 mm3, P < 0.05) and a higher vascular score (2.7 vs 1, P < 0.001), while the index of arterial compliance was similar in the two groups. In conclusion, in mild essential hypertension a baroreceptor dysfunction could be strictly linked to a derangement of the carotid artery structure, while arterial compliance does not seem to involve the baroreceptor function.