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Technical Brief

Computational Investigation of Transmural Differences in Left Ventricular Contractility

[+] Author and Article Information
Hua Wang, Xiaoyan Zhang

Department of Mechanical Engineering,
University of Kentucky,
Lexington, KY 40506-0503

Shauna M. Dorsey, Jason A. Burdick

Department of Bioengineering,
University of Pennsylvania,
Philadelphia, PA 19104-6321

Jeremy R. McGarvey, Joseph H. Gorman, III, Robert C. Gorman

Gorman Cardiovascular Research Group,
University of Pennsylvania,
Philadelphia, PA 19104-5156;
Department of Surgery,
University of Pennsylvania,
Philadelphia, PA 19104

Kenneth S. Campbell

Department of Physiology,
University of Kentucky,
Lexington, KY 40536-0298

James J. Pilla

Gorman Cardiovascular Research Group,
University of Pennsylvania,
Philadelphia, PA 19104-5156;
Department of Surgery,
University of Pennsylvania,
Philadelphia, PA 19104;
Department of Radiology,
University of Pennsylvania,
Philadelphia, PA 19104

Jonathan F. Wenk

Department of Mechanical Engineering,
University of Kentucky,
Lexington, KY 40506-0503;
Department of Surgery,
University of Kentucky,
Lexington, KY 40536-0298
e-mail: jonathan.wenk@uky.edu

1Corresponding author.

Manuscript received May 13, 2016; final manuscript received August 18, 2016; published online October 21, 2016. Assoc. Editor: Jessica E. Wagenseil.

J Biomech Eng 138(11), 114501 (Oct 21, 2016) (6 pages) Paper No: BIO-16-1197; doi: 10.1115/1.4034558 History: Received May 13, 2016; Revised August 18, 2016

Myocardial contractility of the left ventricle (LV) plays an essential role in maintaining normal pump function. A recent ex vivo experimental study showed that cardiomyocyte force generation varies across the three myocardial layers of the LV wall. However, the in vivo distribution of myocardial contractile force is still unclear. The current study was designed to investigate the in vivo transmural distribution of myocardial contractility using a noninvasive computational approach. For this purpose, four cases with different transmural distributions of maximum isometric tension (Tmax) and/or reference sarcomere length (lR) were tested with animal-specific finite element (FE) models, in combination with magnetic resonance imaging (MRI), pressure catheterization, and numerical optimization. Results of the current study showed that the best fit with in vivo MRI-derived deformation was obtained when Tmax assumed different values in the subendocardium, midmyocardium, and subepicardium with transmurally varying lR. These results are consistent with recent ex vivo experimental studies, which showed that the midmyocardium produces more contractile force than the other transmural layers. The systolic strain calculated from the best-fit FE model was in good agreement with MRI data. Therefore, the proposed noninvasive approach has the capability to predict the transmural distribution of myocardial contractility. Moreover, FE models with a nonuniform distribution of myocardial contractility could provide a better representation of LV function and be used to investigate the effects of transmural changes due to heart disease.

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Figures

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Fig. 1

Representative animal-specific FE model of a porcine LV with three transmural layers. (a) 3D view, (b) short axis view, and (c) long axis view.

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Fig. 2

Visual representation of transmural distribution of maximum isometric tension in case 3

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Fig. 3

Visual representation of transmural distribution of maximum isometric tension in case 4

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Fig. 4

Transmural distribution of (a) circumferential, (b) longitudinal,and (c) circumferential–longitudinal strain at end-systole in the free wall of mid-LV. Values were mean ± standard error of the mean (SEM); n = 4 animals. Circles: experimental values. Triangles: FE results using uniformly distributed reference sarcomere length and maximum isometric tension (case 1). Squares: FE results using transmurally varying reference sarcomere length and maximum isometric tension (case 3).

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Fig. 5

Apex twist angle (degrees) calculated in the FE models for each of the cases. Values were mean±SEM; n = 4 animals.

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