Objectives: Contractile function in the normally perfused infarct borderzone (BZ) is depressed. However, the impact of reduced BZ contractility on left ventricular (LV) pump function is unknown. As a consequence, there have been no therapies specifically designed to improve BZ contractility. We tested the hypothesis that an improvement in borderzone contractility will improve LV pump function. Methods: From a previously reported study, magnetic resonance imaging (MRI) images with non-invasive tags were used to calculate 3D myocardial strain in five sheep 16 weeks after anteroapical myocardial infarction. Animal-specific finite element (FE) models were created using MRI data and LV pressure obtained at early diastolic filling. Analysis of borderzone function using those FE models has been previously reported. Chamber stiffness, pump function (Starling’s law) and stress in the fiber, cross fiber, and circumferential directions were calculated. Animal-specific FE models were performed for three cases: (a) impaired BZ contractility (INJURED); (b) BZ-contractility fully restored (100% BZ IMPROVEMENT); or (c) BZ-contractility partially restored (50% BZ IMPROVEMENT). Results: 100% BZ IMPROVEMENT and 50% BZ IMPROVEMENT both caused an upward shift in the Starling relationship, resulting in a large (36 and 26%) increase in stroke volume at LVPED = 20 mmHg (8.0 ml, p < 0.001). Moreover, there were a leftward shift in the end-systolic pressure volume relationship, resulting in a 7 and 5% increase in LVPES at 110 mmHg (7.7 ml, p < 0.005). It showed that even 50% BZ IMPROVEMENT was sufficient to drive much of the calculated increase in function. Conclusion: Improved borderzone contractility has a beneficial effect on LV pump function. Partial improvement of borderzone contractility was sufficient to drive much of the calculated increase in function. Therapies specifically designed to improve borderzone contractility should be developed.
Keywords: myocardial Infarction, borderzone, finite element
Citation: Zhang Z, Sun K, Saloner DA, Wallace AW, Ge L, Baker AJ, Guccione JM and Ratcliffe MB (2012) The benefit of enhanced contractility in the infarct borderzone: a virtual experiment. Front. Physio. 3:86. doi: 10.3389/fphys.2012.00086
Received: 14 December 2011; Accepted: 22 March 2012;
Published online: 09 April 2012.
Edited by:Guillermo A. Cecchi, IBM Watson Research Center, USA
Reviewed by:Flavio H. Fenton, Cornell University, USA
Copyright: © 2012 Zhang, Sun, Saloner, Wallace, Ge, Baker, Guccione and Ratcliffe. This is an open-access article distributed under the terms of the Creative Commons Attribution Non Commercial License, which permits non-commercial use, distribution, and reproduction in other forums, provided the original authors and source are credited.
*Correspondence: Mark B. Ratcliffe, Surgical Service (112), San Francisco Veterans Affairs Medical Center, 4150 Clement Street, San Francisco, CA 94121, USA. e-mail: firstname.lastname@example.org