Static versus Dynamic Distensibility of the Carotid Artery in Humans

In clinical studies, the elastic behavior of central arteries is usually assessed by measuring dynamic distensibility. In this study, we aimed to investigate how dynamic and static distensibility of the common carotid artery (Ddyn and Dstat, respectively) are related in 28 healthy volunteers of 20–71 years. The carotid diameter and its change with the pressure pulse were measured using an ultrasound echo-tracking device. Arterial blood pressure was measured by Finapres and carotid pressure was determined by applanation tonometry. Ddyn was determined at rest using the pressure pulse, while Dstat was determined during pressor responses induced by handgrip or cold pressor test. Data are given as mean ± 1 SD. In younger subjects (<35 years), Dstat did not differ from Ddyn (7.0 ± 3.4 vs. 6.5 ± 2.1·10–³·mm Hg–¹, respectively), whereas in older subjects (>35 years), Dstat was significantly higher than Ddyn (3.8 ± 1.4 vs. 2.1 ± 0.9· 10–³·mm Hg–¹, p < 0.001). For all subjects, Dstat and Ddyn decreased with increasing age and mean arterial pressure (MAP). Using stepwise multiple regression analysis, the strongest predictor of Dstat proved to be MAP, while that of Ddyn was age. Dstat was found to be linearly related to the hysteresis loop area of the pressure-diameter relation (r = 0.94), i.e. to vessel wall viscosity. It is concluded that, with increasing age, static distensibility overestimates the distension capacity of large arteries.