Pressure-corrected carotid stiffness and Young's modulus: evaluation in an outpatient clinic setting.

BACKGROUND Conventional measures for assessing arterial stiffness are inherently pressure-dependent. Whereas statistical pressure adjustment is feasible in (larger) populations, it is unsuited for the evaluation of an individual patient. Moreover, statistical "correction" for blood pressure may actually correct for: (1) the acute dependence of arterial stiffness on blood pressure at the time of measurement; and/or (2) the remodelling effect that blood pressure (hypertension) may have on arterial stiffness, but it cannot distinguish between these processes. METHODS We derived - assuming a single-exponential pressure-diameter relationship - three theoretically pressure-independent carotid stiffness measures suited for individual patient evaluation: (1) stiffness index β0, (2) pressure-corrected carotid pulse wave velocity (cPWVcorr), and (3) pressure-corrected Young's modulus (Ecorr). Using linear regression analysis, we evaluated in a sample of the CATOD study cohort changes in mean arterial pressure (∆MAP) and comparatively the changes in the novel (∆β0, ∆cPWVcorr, ∆Ecorr) as well as conventional (∆cPWV, ∆E) stiffness measures after a 2.9±1.0-year follow-up. RESULTS We found no association between ∆MAP and ∆β0, ∆cPWVcorr, or ∆Ecorr. In contrast, we did find a significant association between ∆MAP and conventional measures ∆cPWV and ∆E. Additional adjustments for biomechanical confounders and traditional risk factors did neither materially change these associations nor the lack thereof. CONCLUSIONS Our newly proposed pressure-independent carotid stiffness measures avoid the need for statistical correction. Hence, these measures (β0, cPWVcorr, Ecorr) can be used in a clinical setting for (1) patient-specific risk assessment and (2) investigation of potential remodelling effects of (changes in) blood pressure on intrinsic arterial stiffness.