New modalities of ultrasound-based intima-media thickness, arterial stiffness and non-coronary vascular calcifications detection to assess cardiovascular risk

BACKGROUND

Carotid intima-media thickness (c-IMT), arterial stiffness (AS) and vascular calcification (VC) are now considered important new markers of atherosclerosis and have been associated with increased prevalence of cardiovascular events. An accurate, reproducible and easy detection of these parameters could increase the prognostic value of the traditional cardiovascular risk factors in many subjects at low and intermediate risk. Today, c-IMT and AS can be measured by ultrasound, while cardiac computed tomography is the gold standard to quantify coronary VC, although concern about the reproducibility of the former and the safety of the latter have been raised. Nevertheless, a safe and reliable method to quantify non-coronary (i.e., peripheral) VC has not been detected yet.

AIM

To review the most innovative and accurate ultrasound-based modalities of c-IMT and AS detection and to describe a novel UltraSound-Based Carotid, Aortic and Lower limbs Calcification Score (USB-CALCs, simply named CALC), allowing to quantify peripheral calcifications. Finally, to propose a system for cardiovascular risk reclassification derived from the global evaluation of "Quality Intima-Media Thickness", "Quality Arterial Stiffness", and "CALC score" in addition to the Framingham score.

Physical and technical principles

Ultrasound is an important technique for studying neurovascular pathology. As with any measurement or imaging technique, it has strengths and weaknesses, and there are a number of potential pitfalls for those interpreting its results. This chapter describes the basic physics and instrumentation behind both imaging and Doppler ultrasound techniques, with a special emphasis on their application to the cerebral circulation. The nature of ultrasound propagation in tissue is described, and the speed of ultrasound, its attenuation, and its behaviour at boundaries of various types are discussed. A description of pulse-echo B-mode techniques includes a section on transducers and artefacts. Doppler ultrasound is particularly important in the study of blood flow, and embolus detection, and its basic principles and various instrument types are described. The uses of transcranial Doppler for the measurement of velocity, flow changes, cerebrovascular resistance, and embolus detection are described. Finally the safety of ultrasound techniques in the context of cerebral vessels and in particularly transcranial Doppler is discussed.

Pulsed Doppler sonography for the guidance of vein puncture: a prospective study

Blind deep venous puncture is an invasive procedure with risks of serious complications compromising the availability of veins for future punctures or endangering the patient's life. We designed a new hand-held pulsed Doppler probe for coaxial guidance of the puncture needle and a dedicated pulsed Doppler device displaying the depth of the measurement volume. We used this technique prospectively in two independent centers (the nephrology department and the intensive care unit) involving senior as well as junior staff members. Either the non-Doppler or the Doppler method were randomly selected for subclavian vein catheterization in 100 patients and for internal jugular vein catheterization in 30 patients. The success rate on the first attempt was 86.2% for the non-Doppler method versus 96.8% for the Doppler method (p = 0.03). The failure rate of the non-Doppler method used by junior staff members was 9.2%, reduced to 1.5% (p = 0.05) by secondary use of the Doppler method and/or help from a senior staff member (rescue procedure). Pulsed Doppler guidance reduced significantly the failure rate of venous punctures especially when used by seniors or by juniors after a training period.