Abstract-Several methodologically independent measures of arterial stiffness derived from either the systolic or diastolic segments of the arterial pulse have been proposed. The exact nature of the large and small artery elasticity indices (C1 and C2, respectively) derived from diastolic pulse contour analysis remains largely unexplored, although C2 has controversially been termed to be "oscillatory" and "reflective." We investigated the relation between C2 and, respectively, a prototype of arterial reflectivity (ie, the augmentation index, AIx) and a covariate of arterial reflectivity (body height). A validated transfer function is used to transform a tonometrically obtained radial pressure wave into an ascending aortic pressure wave, from which AIx is derived using systolic pulse contour analysis. Diastolic pulse contour analysis using a modified Windkessel model is used to derive C1 and C2. H emodynamics research has shifted away from a steadyflow approach toward a pulsatile flow approach, because the former was less predictive in relation to cardiovascular morbidity and mortality. [1][2][3][4][5] The growing importance of pulsatile pressure indices (systolic blood pressure [SBP] and pulse pressure) paralleled the notion that not only increases in systemic vascular resistance (SVR) but also increases in arterial stiffness are important in the pathophysiology of hypertension. 6,7 This interest in the arterial cushioning function of pulsatile flow has given us a myriad of arterial stiffness indices generated by a wide array of methodologically varied noninvasive measurement techniques. 8 -10 Several working definitions of arterial stiffness have been introduced: parameters of compliance or distensibility, which essentially express changes in mono-dimensional, bidimensional, or tridimensional space for a given pressure difference; parameters quantifying speed of wave propagation along an arterial segment (pulse-wave velocity); and parameters of global vascular elastic behavior derived from the arterial pressure pulse waveform.Given the complexity of the latter approach, simplified mathematical models have been developed. 9 The arterial pressure pulse waveform can be regarded as the result of incident (anterograde) and reflected (retrograde) pressure waves. [11][12][13] Wave reflection occurs at sites of discontinuity in calibre (bifurcations, branching points, and arterioles) or discontinuity in elastic properties (atherosclerosis) along the arterial tree. 14 Changes in amplitude and timing of wave reflections play a key role in aortic hemodynamics and, on a broader level, give us information on how the arterial vasculature affects the heart. [15][16][17][18][19] The SphygmoCor BPAS-1/A device (model SPT-301, PWV Medical Pty Ltd) calculates a number of parameters of ventriculo-arterial coupling and wave reflectance, of which the augmentation index (AIx) is preeminent. 11,20,21 Another approach in analyzing the arterial pulse is to regard the waveform as a basic pattern of exponential decay on which damped oscil...

No abstract