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

Abstract

BackgroundKnowledge 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.MethodsWe 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.ResultsThe 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.ConclusionsThe 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12968-016-0317-3) contains supplementary material, which is available to authorized users.

Imaging-Based Simulations for Predicting Sudden Death and Guiding Ventricular Tachycardia Ablation

“…Fiber orientation in GZ, as estimated by the methodology described above, was the subject of concern, as there could be some level of fiber rearrangement not captured by those methodologies. The high-resolution imaging study by by Pashakhanloo et al 30 who used sub-millimeter-resolution DT and LGE-MRI on a clinical scanner to examine the detailed organization of the infarct structure in the ventricles. The study demonstrated that the epi-to-endo progression of the diffusion tensor primary eigenvector is preserved in infarcted parts of the wall in human (Figure 2) and in porcine hearts, justifying the adoption of a rule-based approach to fiber orientation estimation in the zone of infarct.…”

“…C Transmural angle profiles measured in two segments from non-infarcted and infarcted regions ( a and b in panel A left ). Modified from Pashakhanloo et al 30 under the Creative Commons license.…”

Myocardial Scar Delineation Using Diffusion Tensor Magnetic Resonance Tractography

“…In addition, abnormalities in HA may not be seen in all cases of myocardial injury,40 although calculating HA variance improves sensitivity for infarct detection 41. PA, in contrast, is highly uniform throughout the normal LV except for small areas at the apex and right ventricular insertion points.…”

Automatic estimation of Purkinje‐Myocardial junction hot‐spots from noisy endocardial samples: A simulation study

“…For instance, the arrangement of cardiomyocytes in the atria and ventricles follows a specific configuration that has been studied both in animal and human hearts and has permitted the definition of mathematical models that describe it . To obtain the patient‐specific fibre orientation of the ventricular tissue, non‐trivial techniques such as diffusion tensor MRI have to be used . However, because of the long acquisition times required and the fact that the heart is beating only a few heart planes can be imaged in vivo, and the rest have to be interpolated, which hampers the original goal.…”

“…8 To obtain the patient-specific fibre orientation of the ventricular tissue, non-trivial techniques such as diffusion tensor MRI have to be used. 9 However, because of the long acquisition times required and the fact that the heart is beating only a few heart planes can be imaged in vivo, and the rest have to be interpolated, which hampers the original goal.…”