Abstract P1117: Dissimilarities Between and Carotid and Forearm Pressure-Decay and Windkessel Parameters: Implications for Circulatory Models

Abstract

We studied whether: 1) the carotid and forearm diastolic pressure-decay time constants (tau) are similar and 2) the associated Windkessel (WK)-derived compliance and stiffness values are also similar and are related to arterial stiffness. Ambulatory normotensive and hypertensive subjects were studied after 30 minutes of supine rest with radial and carotid arterial tonometry (Sphygmocor), standard oscillometric cuff BP, and central (heart-femoral, hf) and peripheral (femoral-ankle, fa) pulse wave velocity (PWV, Colin VP1000). Brachial and carotid Doppler flow studies were performed in a subset. Tonograms were photo-digitized and the pressure in late diastole was modeled as an exponential decay to an asymptote A with time constant tau and start-decay time t0. [Resistance = mean pressure/flow; WK compliance = tau/resistance and WK stiffness = 1/WK compliance.] Tonometry and PWV data were available in 98 individuals; carotid and forearm blood flow in 22: (mean[SD]) age 50[20] years, weight 81[17] kg, BP 134/77[17/12] mmHg, resting HR 66[12], 38% female. Data are presented in the Table; hfPWV and faPWV were well correlated (p<0.001) but neither was correlated with carotid or forearm tau or the corresponding regional WK stiffness. We conclude that diastolic pressure decay (tau) and WK stiffness (or compliance) are not systemic indicators but rather unique regional characteristics not related to central or peripheral large artery stiffness. These findings suggest that single-WK models do not adequately represent the arterial circulation.