Pulsed Doppler: Diameter, Blood Flow Velocity

Diameter, blood flow velocity and volumic flow of the brachial artery were measured in 36 patients with sustained essential hypertension and compared with 25 normal subjects. Both hypertensives and control subjects were classified according to age into those younger than and those older than 40 years. For the determinations, a pulsed Doppler velocimeter with an adjustable range-gated time system and a double transducer probe was used. With the apparatus, the error in the determination of the angle between the ultrasound beam and the flowing stream of blood was less than 2%. In addition, the overestimation of the arterial diameter due to the sample volume size did not exceed 0.035 ± 0.015 cm. In hypertensives, the diameter of the brachial artery was significantly increased. The value was 0.482 ± 0.013 cm in subjects younger than 40 years and 0.517 ± 0,013 cm in those older than 40 years; in the corresponding controls, the values were 0.422 ± 0.011 cm and 0.436 + 0.013 cm (p < 0.01; p < 0.001). Blood flow velocity was reduced (p < 0.05; p < 0.01) and volumic flow remained within normal ranges. Both in the younger and the older groups, a significant positive correlation was observed between mean arterial pressure and the arterial diameter (r = 0.75; r = 0.60). In hypertensives, i.v. dihydralazine decreased mean arterial pressure from 120 ± 7 to 102 ± 7 mm Hg (p < 0.001). Arterial diameter also significantly decreased (p < 0.01) and returned toward normal. The study demonstrated that the diameter of the brachial artery was significantly increased in sustained essential hypertension and suggested that, with the chronic elevation of blood pressure, the large arteries dilate excessively, contributing to the maintainence of arterial blood flow within normal ranges.