Abstract
Background: A large amount of engineering and medical research has been devoted to the assessment of aortic valve stenosis severity in the past decades. The net transvalvular pressure drop has been recognized as one of the parameters that better reflect stenosis effects on left ventricle overload, and its adoption in clinical assessment of stenosis has been proposed. Flow unsteadiness has been shown to have a non-negligible impact on the net drop; however, a simple formulation for net drop calculation that includes not only flow pulsatility but also the effects of valve dynamics is still lacking. Objective: The present contribution is hence aimed at developing a complete unsteady one-dimensional model of the net aortic transvalvular pressure drop that just requires non-invasive data to be implemented. Methods: Transvalvular flow is described as a jet of incompressible viscous fluid through a circular orifice placed in a concentric rigid circular tube. The classical one-dimensional mass and total head conservation equations are applied. The effective orifice area and transvalvular flow rate are assumed to vary with time throughout the ejection period. Results: The model is found to capture pressure drop oscillations occurring when the valve opens/closes and/or leaflets flutter, thanks to the inclusion of valve dynamics effects. The model is also proposed as a numerical tool for the calculation of the instantaneous effective orifice area once net pressure drop and flow rate are known. Conclusion: The model may contribute to the improvement of non-invasive aortic stenosis assessment.
Highlights
Clinical non-invasive assessment of heart valves hemodynamics and in-vitro assessment of prosthetic valves performance are fundamental issues widely investigated in the literature in the past decades
The model may contribute to the improvement of non-invasive aortic stenosis assessment
The instantaneous net pressure drop predicted by the present model for the hemodynamic conditions depicted in Fig. (3a) is shown in Fig. (5a), together with the Δpnet waveform measured in in-vitro tests [19]
Summary
Clinical non-invasive assessment of heart valves hemodynamics and in-vitro assessment of prosthetic valves performance are fundamental issues widely investigated in the literature in the past decades. Native aortic valve stenosis (AS) is the most common valvular disease in the western countries, and its incidence is destined to increase due to the aging population. It is a pathologic state characterized by a valvular orifice area smaller than the healthy one. A large amount of engineering and medical research has been devoted to the assessment of aortic valve stenosis severity in the past decades. The net transvalvular pressure drop has been recognized as one of the parameters that better reflect stenosis effects on left ventricle overload, and its adoption in clinical assessment of stenosis has been proposed. Flow unsteadiness has been shown to have a non-negligible impact on the net drop; a simple formulation for net drop calculation that includes flow pulsatility and the effects of valve dynamics is still lacking
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