Submillimeter diffusion tensor imaging and late gadolinium enhancement cardiovascular magnetic resonance of chronic myocardial infarction

• Published in: Journal of cardiovascular magnetic resonance Vol. 19; no. 1; p. 9
• Main Authors: Pashakhanloo, Farhad, Herzka, Daniel A, Mori, Susumu, Zviman, Muz, Halperin, Henry, Gai, Neville, Bluemke, David A, Trayanova, Natalia A, McVeigh, Elliot R
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 11.01.2017; BioMed Central
• Subjects: Aged, 80 and over; Animals; Anisotropy; Care and treatment; Chronic Disease; Contrast Media - administration & dosage; Diffusion Tensor Imaging; Disease Models, Animal; Female; Fibrosis; Gadolinium; Gadolinium DTPA - administration & dosage; Heart attack; Humans; Image Interpretation, Computer-Assisted; Imaging, Three-Dimensional; Magnetic resonance imaging; Magnetic Resonance Imaging - methods; Myocardial Infarction - diagnostic imaging; Myocardial Infarction - pathology; Myocardial Infarction - physiopathology; Myocardium - pathology; Predictive Value of Tests; Risk factors; Sus scrofa; Ventricular Remodeling; Myocardial infarction; Microstructural remodeling; Late gadolinium enhancement; Fiber structure; Diffusion tensor imaging
• ISSN: 1097-6647; 1532-429X
• DOI: 10.1186/s12968-016-0317-3

Knowledge of the three-dimensional (3D) infarct structure and fiber orientation remodeling is essential for complete understanding of infarct pathophysiology and post-infarction electromechanical functioning of the heart. Accurate imaging of infarct microstructure necessitates imaging techniques that produce high image spatial resolution and high signal-to-noise ratio (SNR). The aim of this study is to provide detailed reconstruction of 3D chronic infarcts in order to characterize the infarct microstructural remodeling in porcine and human hearts. We employed a customized diffusion tensor imaging (DTI) technique in conjunction with late gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) on a 3T clinical scanner to image, at submillimeter resolution, myofiber orientation and scar structure in eight chronically infarcted porcine hearts ex vivo. Systematic quantification of local microstructure was performed and the chronic infarct remodeling was characterized at different levels of wall thickness and scar transmurality. Further, a human heart with myocardial infarction was imaged using the same DTI sequence. The SNR of non-diffusion-weighted images was >100 in the infarcted and control hearts. Mean diffusivity and fractional anisotropy (FA) demonstrated a 43% increase, and a 35% decrease respectively, inside the scar tissue. Despite this, the majority of the scar showed anisotropic structure with FA higher than an isotropic liquid. The analysis revealed that the primary eigenvector orientation at the infarcted wall on average followed the pattern of original fiber orientation (imbrication angle mean: 1.96 ± 11.03° vs. 0.84 ± 1.47°, p = 0.61, and inclination angle range: 111.0 ± 10.7° vs. 112.5 ± 6.8°, p = 0.61, infarcted/control wall), but at a higher transmural gradient of inclination angle that increased with scar transmurality (r = 0.36) and the inverse of wall thickness (r = 0.59). Further, the infarcted wall exhibited a significant increase in both the proportion of left-handed epicardial eigenvectors, and in the angle incoherency. The infarcted human heart demonstrated preservation of primary eigenvector orientation at the thinned region of infarct, consistent with the findings in the porcine hearts. The application of high-resolution DTI and LGE-CMR revealed the detailed organization of anisotropic infarct structure at a chronic state. This information enhances our understanding of chronic post-infarction remodeling in large animal and human hearts.