Flow velocity patterns in and distensibility of the carotid artery bulb in subjects of various ages.

Velocity patterns in and distensibility of the carotid artery bulb were studied in younger (20 to 30 years; n = 11) and older (50 to 60 years; n = 9) volunteers without detectable lesions of the cervical carotid arteries by means of a high-resolution, multigate, pulsed Doppler system coupled to a B mode imager. In the bulb the axial velocities were highest on the side of the flow divider, while regions of flow separation and recirculation were observed on the side opposite to this divider. Flow separation and recirculation were less pronounced and less common in the older subjects. Flow separation was not continuously present throughout the cardiac cycle. The distensibility of the carotid arteries was significantly diminished in older subjects, especially in the bulb. The velocity patterns in the carotid artery bulb of younger subjects corroborate the patterns observed in models. The diminished flow separation and recirculation in the older subjects might result from alterations in distensibility at the transition from common to internal carotid artery with increasing age.