The study of cardiovascular parameters in exercise is intriguing, since this evaluation could provide information about dynamic conditions, mimicking patient’s real life. Therefore, we evaluated carotid cross-sectional distensibility coefficient (DC), systemic vascular resistance corrected by cardiac frequency (SVRI_T), arterial elastance (Ea) and left-ventricular elastance (Elv) during graded bicycle semi-supine exercise test.

In 18 healthy subjects (9 men, 34±3 years) cardiac volumes were estimated from 2D transthoracic echocardiography, right carotid diameter and distension by an automatic system (Carotid Studio, IFC-CNR) applied to ultrasound B-mode image sequences and central pressures by tonometry. All measurements were performed at 60%, 70%, 80% and 85% (peak) of the age-dependent maximal heart rate.

During exercise DC decreased (peak versus rest: −17.8% and p<0.05), and SVRI_T did not significantly change. Ea increased (+21.3%, p<0.01) and, since Elv presented a greater variation (+69.2%, p<0.001), arterial ventricular coupling (Ea/Elv) decreased (−22.6%, p<0.05). As expected, central pulse pressure was significantly increased (+81.8%, p<0.01).

In conclusion, carotid stiffness increased during exercise, possibly due to the recruitment of more collagen fibers and the consequent different mechanical behavior of arterial walls at higher pressures. Since SVRI_T did not change significantly, the increased arterial stiffness, observed at carotid site, might represent the main determinant of Ea variation. Finally, a decrease in arterial-ventricular coupling during exercise was confirmed.

Our results show the feasibility of a simultaneous multi-sites approach that could help in the understanding of arterial physiology and patho-physiology in stress conditions.