• biomarcatori cardiovascolari
• carotide
• elasticità arteriosa
• esercizio

The behaviour of cardiovascular parameters during exercise remains unsettled. Arterial stiffness is one of the most promising and innovative vascular biomarkers; this vessel property is usually evaluated at rest, but, since it aims to describe a stress-strain vessel behaviour, it is not a static parameter. Hence, our aim was to develop a method able to evaluate carotid elasticity dynamically in order to investigate if this analysis can provide information regarding differences between populations (i.e. patients and healthy subjects). We developed an approach based on a contour tracking algorithm applied to ultrasound B-mode image sequences and used it in conjunction with a local pressure estimation to assess carotid distensibility. The method's reproducibility was evaluated by analyzing a group of healthy volunteers during two sessions 3 days apart. Repeatability was expressed as coefficient of variation and satisfactory results were obtained in exercise.
After testing the robustness of the technique, the approach was applied during graded bicycle semi-supine exercise session in patients with known or suspected coronary artery disease (CAD) and results were compared with a control group. 36 consecutive patients (20 men, 61±8years), and 18 healthy volunteers (9 men, 34±3 years) were recruited. Right carotid diameter (D) and distension (ΔD) were estimated by the developed ultrasound B-mode image processing method, and central pulse pressure (PPa) by radial tonometry; then, carotid elasticity was expressed as cross-sectional distensibility coefficient (DC). Besides the vascular evaluation we introduced the estimation of left-ventricular elastance (ElvI) by echocardiography, in order to obtain a more integrated dynamic picture including arterial-ventricular coupling. All measurements were performed at rest, peak of age-dependent maximal heart rate and during recovery.
At rest, D and PPa were higher in patients than in controls, whereas no significant differences were observed in ΔD and mean blood pressure; DC and ElvI were lower in patients than in healthy volunteers. At peak mean blood pressure increased both in patients and controls; DC significantly decreased and D increased in healthy subjects but not in patients. Finally ElvI highly increased in controls but not in patients. Behaviours of the two populations during recovery were similar.
Hence, we can conclude that the developed approach provides a suitable reproducibility for clinical studies and was able to dynamically discriminate between different kind of subjects. In particular, in patients with known or suspected CAD, carotid distensibility, which at rest is lower than in healthy controls, remains unchanged during maximal exercise, despite a similar increase in mean blood pressure in the two populations. This difference is underlined also by the absence of strong cardiac response and carotid vasodilation in the pathologic population.
From our preliminary results, the importance of a dynamic assessment of carotid elasticity was confirmed, and there is evidence of a clinical need including a simple and robust device to more easily perform this kind of analysis than by ultrasound. In our lab a first prototype based on vibration approach was designed and might be the suitable solution for implementing low-cost and easy carotid elasticity dynamic evaluation.
In the future, the cardiologist ambulatory might provide, besides cardiac and pressure monitoring, additive relevant clinical information from an arterial elasticity 24-hours device.