Abstract
Pressure–velocity-based analysis of arterial wave intensity gives clinically relevant information about the performance of the heart and vessels, but its utility is limited because accurate pressure measurements can only be obtained invasively. Diameter–velocity-based wave intensity can be obtained noninvasively using ultrasound; however, due to the nonlinear relationship between blood pressure and arterial diameter, the two wave intensities might give disparate clinical indications. To test the magnitude of the disagreement, we have generated an age-stratified virtual population to investigate how the two dominant nonlinearities, viscoelasticity and strain-stiffening, cause the two formulations to differ. We found strong agreement between the pressure–velocity and diameter–velocity methods, particularly for the systolic wave energy, the ratio between systolic and diastolic wave heights, and older subjects. The results are promising regarding the introduction of noninvasive wave intensities in the clinic.
Highlights
Analysis of wave intensity (WI)[1] is clinically useful, as arterial waves carry information about the performance of the heart and blood vessels,[2,3,4,5,6] but its utility is restricted by its reliance upon measurements of blood pressure with high temporal resolution, which can only be measured invasively or estimated inaccurately from noninvasive methods
The prefix n refers to the noninvasive method, and invasive and noninvasive WI refer to those calculated with the theoretical pulse wave velocity (PWV), unless otherwise stated
The separated waves calculated with the loop-derived PWV match those calculated with the theoretical PWV well, except in the case of the invasive WI in the carotid, where instead they are close to the unseparated WI
Summary
Analysis of wave intensity (WI)[1] is clinically useful, as arterial waves carry information about the performance of the heart and blood vessels,[2,3,4,5,6] but its utility is restricted by its reliance upon measurements of blood pressure with high temporal resolution, which can only be measured invasively or estimated inaccurately from noninvasive methods. To obviate this restriction, Feng and Khir[7] introduced a new formulation of WI that instead relies only upon diameter and velocity; both can be obtained from spatiotemporally coincident ultrasound images, but there is a lack of research on the efficacy of this noninvasive formulation as a surrogate for conventional WI. This reduced-order modelling provides an effective means of studying arterial wave propagation, as it has the capacity to simulate complex networks with reasonable computational cost[10,11] and has been validated against in-vitro[10,12] and in-vivo[13,14,15] data
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