Pulsed Tissue Doppler Imaging and Aortic Stiffness

There is a growing interest regarding the link between arterial stiffness and cardiovascular (CV) risk. A boost in this area of research was the publication in 2006 of an expert consensus document on methodological issues and clinical applications of arterial stiffness. In this document, the aorta was identified as the major vessel of interest when determining regional arterial stiffness and aortic pulse wave velocity (aPWV) measured by applanation tonometry as the most simple, noninvasive, robust, and reproducible method. Based on the growing body of evidence and standardization of the methods to evaluate arterial stiffness, aPWV was included in the 2007 European Society of Cardiology/European Society of Hypertension Guidelines for the management of arterial hypertension. Increased aortic stiffness was considered as a measure of subclinical target organ damage and a vascular biomarker. Despite these acknowledgements, the measurement of arterial stiffness remains confined to research purposes. One of the main limitations for a wider use of applanation tonometry to measure aPWV is that this technique requires dedicated devices and expert operators. Therefore, it is difficult to implement applanation tonometry in daily clinical practice. It follows that current research is focused on developing cheaper and easier to use devices. As previously reported, aPWV is a measure of the mean stiffness of the arterial segment (regional stiffness) and it does not include the ascending aorta which makes an important contribution to total aortic compliance. To overcome these limitations, at least in part, several methods and devices have been proposed. Only few of them, such as magnetic resonance imaging and pulsed tissue Doppler imaging, are able to evaluate aortic elasticity of the ascending aorta. In particular, the latter is an interesting and promising technique requiring standard ultrasound equipment which is widely available and skills already acquired by expert sonographers. In this issue of Angiology, Ren et al provide a systematic review on aortic elasticity evaluated by pulsed tissue Doppler imaging of the ascending aorta in different diseases. Pulsed tissue Doppler imaging, measuring aortic wall motion velocity and diameters during systole and diastole, estimates aortic distensibility and aortic stiffness index. Ren et al report that aortic elasticity is not only decreased in CV diseases but also in diseases of other systems that affect the CV system. This is in line with the current concept that increased aortic stiffness could mediate the effect of several diseases (including chronic kidney disease and chronic inflammatory diseases) on the heart and explain, at least in part, why CV risk is increased. More data are needed to confirm that increased ascending aorta stiffness is associated with greater CV risk and to test whether reducing this variable decreases CV risk. Ren et al reported study heterogeneity regarding methodology and outcomes. Similar issues, referred to applanation tonometry and classic techniques for the study of local stiffness, led to the consensus document on methodological issues and clinical applications of arterial stiffness. Considering the potential advantages of pulsed tissue Doppler imaging for the study of the ascending aorta (not explorable with applanation tonometry or current echotracking devices), a standardization of methodology and outcomes is required. In this regard, future validation studies could be designed to compare measures of arterial stiffness calculated by pulsed tissue Doppler imaging with (a) those obtained by gold standard invasive techniques for measuring ascending aorta stiffness, and (b) reference noninvasive techniques for the study of local arterial stiffness (ie, vascular echotracking) in an arterial segment explorable by both techniques (ie, common carotid artery). Moreover, considering that results of pulsed tissue Doppler imaging are operator dependent, a reproducibility test and a Bland-Altman plot could be reported at least in a first article and cited