Radiofrequency-based carotid wall tracking: a comparison between two different systems

Objectives: A direct measurement of carotid stiffness implies an accurate assessment of changes in carotid diameter and pressure during cardiac cycle. Radiofrequency-based wall-tracking systems (WTS) are capable to track arterial wall movement with adequate spatial and temporal resolution, and to provide carotid pressure estimate from calibrated distension waveforms. The aim of the present study was to compare the values of carotid distension and beta-stiffness index acquired in the same population by two commercially available WTS, in order to determine whether their measures can be pooled in clinical studies. In addition, a local carotid pulse pressure (PP) obtained from calibrated distension waveforms was compared with that obtained from pressure waveforms. Methods: In 105 patients, right common carotid artery (CCA) systo-diastolic excursions were assessed during the same session and by the same operator both by WTS implemented in Esaote system (QAS, MyLab) and in Aloka system (E-track; Alpha 10). In 78 patients, carotid PP was also estimated by applanation tonometry. Results: Despite comparable blood pressure and heart rate values during the two acquisitions, CCA distension was significantly lower (363±162 vs. 458±176μm, P<0.0001) and beta-stiffness index (11.9±5.5 vs. 9.4±3.8, P<0.0001) higher with Esaote as compared to Aloka. PP obtained from calibrated pressure and distension waveforms was comparable (42.6±11.4 vs. 43.0±10.7mmHg, P=0.51). Conclusions: The values of carotid distension and stiffness obtained by two different WTS are not interchangeable and cannot be merged into a common database. Calibrated distension curves may provide an acceptable estimate of local carotid pressure