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Research Papers

Computational Study of Hemodynamic Effects of Abnormal E/A Ratio on Left Ventricular Filling

[+] Author and Article Information
Xudong Zheng

Assistant Professor
Department of Mechanical Engineering,
University of Maine,
Boardman Hall 213 A,
Orono, ME 04473
e-mail: xudong.zheng@maine.edu

Qian Xue

Department of Mechanical Engineering,
University of Maine,
Orono, ME 04473

Rajat Mittal

Department of Mechanical Engineering,
Johns Hopkins University,
Baltimore, MD 21218

1Corresponding author.

Manuscript received July 2, 2013; final manuscript received March 14, 2014; accepted manuscript posted March 24, 2014; published online April 25, 2014. Assoc. Editor: Dalin Tang.

J Biomech Eng 136(6), 061005 (Apr 25, 2014) (10 pages) Paper No: BIO-13-1292; doi: 10.1115/1.4027268 History: Revised March 14, 2014; Accepted March 24, 2014; Received June 02, 2014

Three-dimensional numerical simulations are employed to investigate the hemodynamic effects of abnormal E/A ratios on left ventricular filling. The simulations are performed in a simplified geometric model of the left ventricle (LV) in conjunction with a specified endocardial motion. The model has been carefully designed to match the important geometric and flow parameters under the physiological conditions. A wide range of E/A ratios from 0 to infinity is employed with the aim to cover all the possible stages of left ventricle diastolic dysfunction (DD). The effects of abnormal E/A ratios on vortex dynamics, flow propagation velocity, energy consumption as well as flow transport and mixing are extensively discussed. Our results are able to confirm some common findings reported by the previous studies, and also uncover some interesting new features.

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Figures

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Fig. 1

(a) The geometric model of the left ventricle and (b) the time history of the ventricular volume flow rate for various cases

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Fig. 2

The time evolution of the vortical structure during the diastole phase for the normal filling case (E/A = 1.88). The vortical structure is visualized by using the eigenvalue of velocity gradient. (a) t = 0.06T, (b) t = 0.156T, (c) t = 0.22T, (d) t = 0.272T, (e) t = 0.316T, (f) t = 0.448T, (g) t = 0.488T, and (h) t = 0.648T. T is the time for one cardiac cycle. T = 1 s.

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Fig. 3

The velocity vectors and 3D swirl strength at the midaxial plane at three time instants. (a) t = 0.272T, (b) t = 0.316T, and (c) t = 0.648T.

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Fig. 4

The time evolution of the vortical structure during the diastole phase for the case with E/A = 0.129. The vortical structure is visualized by using the eigenvalue of velocity gradient. (a) t = 0.156T, (b) t = 0.568T, (c) t = 0.604T, (d) t = 0.64T, and (e) t = 0.668T.

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Fig. 5

The flow propagation speed versus the vortex formation time for each E wave and A wave of all the cases. Grey region represents the “strong” filling waves associated with complex vortical structures.

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Fig. 6

(a) A spatiotemporal contour of the flow velocity along the long axis for the normal filling. (b) The variations of the flow propagation speeds with vortex formation number for the E wave and A wave.

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Fig. 7

(a) The instantaneous time rate of the changes of five energetics components of the normal case (E/A = 1.88) during the diastole. The volume flow rate is superimposed at the bottom. (b) The total energy of five components during the diastole versus E/A ratio.

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Fig. 8

(a) The time variation of the volume-averaged pressure inside the LV for the normal filling case; (b) the magnitude of the peak averaged pressure during the acceleration and deceleration for both E wave and A wave versus the amplitude of inflow acceleration

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Fig. 9

The contour of the volume content of the atrial blood inside the LV at five instants during one cycle. (a) t = 0.152TE, (b) t = 0.316T, (c) t = 0.488T, (d) t = 0.568T, and (e) t = 0.648T. The first row is from the normal case (E/A = 1.88) and the second raw is from the diseased case (E/A = 0.129).

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Fig. 10

The variations of the standard deviation of the volume content of the atrial blood from the EF (std) and the volume percentage of the stagnation region inside the LV (stag) with the varying E/A ratio

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