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TECHNICAL BRIEFS

Wave Intensity Analysis of Left Ventricular Filling

[+] Author and Article Information
L. L. Lanoye1

Hydraulics Laboratory, Institute of Biomedical Technology,  Ghent University, BelgiumLieve.Lanoye@UGent.be

J. A. Vierendeels

Department of Flow, Heat and Combustion Mechanics,  Ghent University, Belgium

P. Segers, P. R. Verdonck

Hydraulics Laboratory, Institute of Biomedical Technology,  Ghent University, Belgium

1

Corresponding Author. Telephone: +3292648927; Fax: +3292643595.

J Biomech Eng 127(5), 862-867 (Mar 24, 2005) (6 pages) doi:10.1115/1.1992534 History: Received March 01, 2004; Revised March 24, 2005

Wave intensity analysis (WIA) is a powerful technique to study pressure and flow velocity waves in the time domain in vascular networks. The method is based on the analysis of energy transported by the wave through computation of the wave intensity dI=dPdU, where dP and dU denote pressure and flow velocity changes per time interval, respectively. In this study we propose an analytical modification to the WIA so that it can be used to study waves in conditions of time varying elastic properties, such as the left ventricle (LV) during diastole. The approach is first analytically elaborated for a one-dimensional elastic tube-model of the left ventricle with a time-dependent pressure-area relationship. Data obtained with a validated quasi-three dimensional axisymmetrical model of the left ventricle are employed to demonstrate this new approach. Along the base-apex axis close to the base wave intensity curves are obtained, both using the standard method and the newly proposed modified method. The main difference between the standard and modified wave intensity pattern occurs immediately after the opening of the mitral valve. Where the standard WIA shows a backward expansion wave, the modified analysis shows a forward compression wave. The proposed modification needs to be taken into account when studying left ventricular relaxation, as it affects the wave type.

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Copyright © 2005 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

Panel (a): The flow velocity profile imposed at the mitral valve in the computational model. At the start of the relaxation (t=0s) the valves are closed and the imposed flow velocity is zero. Once the ventricular pressure drops below the left atrial pressure the velocity profile is no longer zero and the early filling phase starts (E-peak). After t=0.3s a second peak A occurs due to atrial contraction. The imposed profile is uniform. Panel (b): Plot of the flow velocity pattern in the left ventricle at the top of the A-peak (atrial contraction).

Grahic Jump Location
Figure 2

Panel (a): The profile of the flow velocity-component parallel to the base-apex axis at 0.5cm starting from the base along the base-apex axis. For all panels time t=0s corresponds to the closure of the aortic valve. After 0.08s the mitral valve opens and the filling phase starts. Panel (b): The ventricular pressure as a function of time at 0.5cm starting from the base along the base-apex axis. Full line: Simulation where the mitral valve opens after 0.08s as described above. Dashed line: Simulation where the mitral valve remains closed during relaxation, this situation was simulated by imposing a mitral velocity zero during diastole. Panel (c): The wave intensity at 0.5cm starting from the base along the base-apex axis. The curve dI′ gives the modified wave intensity, the curve labelled dI gives the standard wave intensity. C: compression wave; E: expansion wave.

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