Estimation of mean aortic pressure

Novel theory and potential applications of central diastolic pressure decay time constant

Central aortic diastolic pressure decay time constant ( τ ) is according to the two-element Windkessel model equal to the product of total peripheral resistance ( R ) times total arterial compliance ( C ). As such, it is related to arterial stiffness, which has considerable pathophysiological relevance in the assessment of vascular health. This study aimed to investigate the relationship of the constant τ with the product T MBP cPP , given by heart period ( T ) times the ratio of mean blood pressure (MBP) to central pulse pressure ( cPP ). The relationship was derived by performing linear fitting on an in silico population of n1 = 3818 virtual subjects, and was subsequently evaluated on in vivo data (n2 = 2263) from the large Asklepios study. The resulted expression was found to be τ = k ' T MBP cPP , withk ' = 0.7 (R2 = 0.9). The evaluation of the equation on the in vivo human data reported high agreement between the estimated and reference τ values, with a correlation coefficient equal to 0.94 and a normalized RMSE equal to 5.5%. Moreover, the analysis provided evidence that the coefficient k ' is age- and gender-independent. The proposed formula provides novel theoretical insights in the relationship between τ and central blood pressure features. In addition, it may allow for the evaluation of τ without the need for acquiring the entire central blood pressure wave, especially when an approximation of the cPP is feasible. This study adds to the current literature by contributing to the accessibility of an additional biomarker, such as the central diastolic pressure decay time constant, for the improved assessment of vascular ageing.

Mean arterial pressure values calculated using seven different methods and their associations with target organ deterioration in a single-center study of 1878 individuals

To assess the differences among seven different methods for the calculation of mean arterial pressure (MAP) and to identify the formula that provides MAP values that are more closely associated with target organ deterioration as expressed by the carotid cross-sectional area (CSA), carotid-to-femoral pulse-wave velocity (cf-PWV) and left ventricular mass (LVM). The study population consisted of 1878 subjects who underwent noninvasive cardiovascular risk assessment. Blood pressure (BP) was assessed in all subjects, and MAP was calculated by direct oscillometry and six different formulas. Carotid artery ultrasound imaging was performed in 1628 subjects. The CSA of the right and left common carotid artery (CCA) were calculated and used as surrogates of arterial wall mass and hypertrophy. Aortic stiffness was evaluated in 1763 subjects by measuring the cf-PWV. Finally, 218 subjects underwent echocardiographic examination for the assessment of LVM. Among the examined methods of MAP calculation, the formula MAP1=[diastolic BP]+0.412 × [pulse pressure] yielded the strongest correlations with the LVM, cf-PWV and CSA of the right and left CCA, even after adjusting for age and gender. The MAP calculation using the 0.412 was superior compared with the traditional formula that uses the 0.33 for the discrimination of subjects with left ventricular and carotid wall hypertrophy, as well as subjects with increased aortic stiffness. MAP estimated with the 0.412 is better correlated with target organ deterioration compared with other formulas. Future studies are needed to explore the accuracy of these formulas for MAP estimation compared with direct intra-arterial BP measurement.