Ex vivo cardiovascular magnetic resonance diffusion weighted imaging in congenital heart disease, an insight into the microstructures of tetralogy of Fallot, biventricular and univentricular systemic right ventricle

Abstract

Purpose Common types of congenital heart disease exhibit a variety of structural and functional variations which may be accompanied by changes in the myocardial microstructure. We aimed to compare myocardial architecture from magnetic resonance diffusion tensor imaging (DTI) in preserved pathology specimens. Materials and methods Pathology specimens (n = 24) formalin-fixed for 40.8 ± 7.9 years comprised tetralogy of Fallot (TOF, n = 10), dextro-transposition of great arteries (D-TGA, n = 8) five with ventricular septal defect (VSD), systemic right ventricle (n = 4), situs inversus totalis (SIT, n = 1) and levo-TGA (L-TGA, n = 1). Specimens were imaged using a custom spin-echo sequence and segmented automatically according to tissue volume fraction. In each specimen T1, T2, fractional anisotropy, mean diffusivity, helix angle (HA) and sheet angle (E2A) were quantified. Pathologies were compared according to their HA gradient, HA asymmetry and E2A mean value in each myocardial segment (anterior, posterior, septal and lateral walls). Results TOF and D-TGA with VSD had decreased helix angle gradient by − 0.34°/% and remained symmetric in the septum in comparison to D-TGA without VSD. Helix angle range was decreased by 45°. It was associated with a decreased HA gradient in the right ventricular (RV) wall, i.e. predominant circumferential myocytes. The sheet angle in the septum of TOF was opposing those of the left ventricular (LV) free wall. Univentricular systemic RV had the lowest HA gradient (− 0.43°/%) and the highest HA asymmetry (75%). HA in SIT was linear, asymmetric, and reversed with a sign change at about 70% of the depth at mid-ventricle. In L-TGA with VSD, HA was asymmetric (90%) and its gradients were decreased in the septum, anterior and lateral wall. Conclusion The organization of the myocytes as determined by DTI differs between TOF, D-TGA, L-TGA, systemic RV and SIT specimens. These differences in cardiac structure may further enlighten our understanding of cardiac function in these diverse congenital heart diseases.

Evaluation of Right Ventricular Function and Myocardial Microstructure in Fetal Hypoplastic Left Heart Syndrome

“…However, decreasing HA gradients indicated that oblique fibers in the ventricular septum were eliminated. Our research results were consistent with those of a preliminary study, all illustrating a reduction in the circumferential muscles, which are right-ventricular-dominant in the lateral wall, but increased oblique fibers [ 36 ]. Hence, the structure of the right ventricle in HLHS fetuses may be closer to a global helix.…”

A groupwise registration and tractography framework for cardiac myofiber architecture description by diffusion MRI: An application to the ventricular junctions

“…A larger number of diffusion directions is recommended for a better estimation of the diffusion tensor [ 67 ]. Recent ex vivo cardiac studies reported a number of gradient directions from 7 [ 68 ], 30 [ 69 ], 32 [ 70 ] to 61 [ 68 ]. Nevertheless, as demonstrated in [ 68 ], the trade-off between signal-to-noise ratio and angular resolution are not the only parameters to take into account.…”

Impact of intraventricular septal fiber orientation on cardiac electromechanical function

“…To limit the voxel averaging of the DTI metrics and depict the heterogeneity of diffusion directions, a relatively high isotropic voxel resolution of 600 µm was picked. Consequently, to maintain a reasonable acquisition time (from 9 to 12 h, depending on the matrix size), the acquisition suffered from a low angular resolution of the DW images in the six directions in comparison with recent studies in rodent species ( 65 ) or human species ( 66 , 67 ).…”