Carotid artery plaque and arterial stiffness: about conflicts between ultrasound and tonometry and between local and global
The so-called arterial stiffness-related indices constitute an ever increasing collection of parameters obtained by methods as different as applanation tonometry, ultrasound, MRI and oscillometry and apply to specific locoregional segments and much longer trajectories of the arterial tree. Most of these indices with a few exceptions definitely belong to the field of experimental and (pre)clinical research. One of these exceptions termed pulse wave velocity (PWV) gained special attention and recently entered the field of clinical routine because of its physiology-based characteristics and robust performance in large cardiovascular outcome studies (evidence-based medicine) [1,2]. Evidence is most compelling for the carotid–femoral modification (cf-PWV), and the 2013 European Society of Hypertension/European Society of Cardiology Guidelines for the management of arterial hypertension  consider increased cf-PWV (>10 m/s) as a cost-effective indicator of asymptomatic organ damage. Brachial–ankle PWV and Cardio-Ankle Vascular Index are gaining popularity, and validation against cardiovascular endpoints is ongoing , but their physiological relevance is disputed by several research groups. Carotid wall thickening (intima–media thickness >0.9 mm) and occurrence of plaque are other accepted markers of asymptomatic organ damage.