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Front. Physiol. | doi: 10.3389/fphys.2018.00826

Microstructural Infarct Border Zone Remodeling in the Post-Infarct Swine Heart Measured by Diffusion Tensor MRI

Geoffrey L. Kung1, 2, 3, Marmar Vaseghi3, 4,  Jin K. Gahm1, 3, 5, Jane Shevtsov3,  Alan Garfinkel3,  Kalyanam Shivkumar3, 4 and  Daniel B. Ennis1, 2, 3*
  • 1Department of Radiological Sciences, University of California, Los Angeles, United States
  • 2Department of Bioengineering, University of California, Los Angeles, United States
  • 3Department of Medicine (Cardiology), University of California, Los Angeles, United States
  • 4Cardiac Arrhythmia Center, University of California, Los Angeles, United States
  • 5Computer Science Department, University of California, Los Angeles, United States

Introduction – Computational models of the heart increasingly require detailed microstructural information to capture the impact of tissue remodeling on cardiac electromechanics in , for example, hearts with myocardial infarctions. Myocardial infarctions are surrounded by the infarct border zone (BZ), which is a site of electromechanical property transition. Magnetic resonance imaging (MRI) is an emerging method for characterizing microstructural remodeling and focal myocardial infarcts and the BZ can be identified with late gadolinium enhanced (LGE) MRI. Microstructural remodeling within the BZ, however, remains poorly characterized by MRI due, in part, to the fact that LGE and DT-MRI are not always available for the same heart. Diffusion tensor MRI (DT-MRI) can evaluate microstructural remodeling by quantifying the DT apparent diffusion coefficient (ADC, increased with decreased cellularity), fractional anisotropy (FA, decreased with increased fibrosis), and tissue mode (decreased with increased fiber disarray). The purpose of this work was to use LGE MRI in post-infarct porcine hearts (N=7) to segment remote, BZ, and infarcted myocardium, thereby providing a basis to quantify microstructural remodeling in the BZ and infarcted regions using co-registered DT-MRI.

Methods – Chronic porcine infarcts were created by balloon occlusion of the LCx. 6-8 weeks post-infarction, MRI contrast was administered, and the heart was potassium arrested, excised, and imaged with LGE MRI (0.33x0.33x0.33mm) and co-registered DT-MRI (1x1x3mm). Myocardium was segmented as remote, BZ, or infarct by LGE signal intensity thresholds. DT invariants were used to evaluate microstructural remodeling by quantifying ADC, FA, and tissue mode.

Results – The BZ significantly remodeled compared to both infarct and remote myocardium. BZ demonstrated a significant decrease in cellularity (increased ADC), significant decrease in tissue organization (decreased FA), and a significant increase in fiber disarray (decreased tissue mode) relative to remote myocardium (all p<0.05). Microstructural remodeling in the infarct was similar, but significantly larger in magnitude (all p<0.05).

Conclusion – DT-MRI can identify regions of significant microstructural remodeling in the BZ that are distinct from both remote and infarcted myocardium.

Keywords: Cardiac computational models, Diffusion Tensor MRI, Border zone, cardiac remodeling, Cardiac electromechanics

Received: 02 Nov 2017; Accepted: 12 Jun 2018.

Edited by:

Julius Guccione, University of California, San Francisco, United States

Reviewed by:

Gernot Plank, Medizinische Universität Graz, Austria
Joakim Sundnes, Simula Research Laboratory, Norway  

Copyright: © 2018 Kung, Vaseghi, Gahm, Shevtsov, Garfinkel, Shivkumar and Ennis. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Daniel B. Ennis, University of California, Los Angeles, Department of Radiological Sciences, Los Angeles, United States, daniel.ennis@gmail.com