On the Estimation of Total Arterial Compliance from Aortic Pulse Wave Velocity
Total arterial compliance (C (T)) is a main determinant of cardiac afterload, left ventricular function and arterio-ventricular coupling. C (T) is physiologically more relevant than regional aortic stiffness. However, direct, in vivo, non-invasive, measurement of C (T) is not feasible. Several methods for indirect C (T) estimation require simultaneous recording of aortic flow and pressure waves, limiting C (T) assessment in clinical practice. In contrast, aortic pulse wave velocity (aPWV) measurement, which is considered as the "gold standard" method to assess arterial stiffness, is noninvasive and relatively easy. Our aim was to establish the relation between aPWV and C (T). In total, 1000 different hemodynamic cases were simulated, by altering heart rate, compliance, resistance and geometry using an accurate, distributed, nonlinear, one-dimensional model of the arterial tree. Based on Bramwell-Hill theory, the formula was found to accurately estimate C (T) from aPWV. Coefficient k was determined both analytically and by fitting C (T) vs. aPWV data. C (T) estimation may provide an additional tool for cardiovascular risk (CV) assessment and better management of CV diseases. C (T) could have greater impact in assessing elderly population or subjects with elevated arterial stiffness, where aPWV seem to have limited prognostic value. Further clinical studies should be performed to validate the formula in vivo.