Mapping cardiac microstructure of rabbit heart in different mechanical states by high resolution diffusion tensor imaging: A proof-of-principle study.
Myocardial microstructure and its macroscopic materialisation are fundamental to the function of the heart. Despite this importance, characterisation of cellular features at the organ level remains challenging, and a unifying description of the structure of the heart is still outstanding. Here, we optimised diffusion tensor imaging data to acquire high quality data in ex vivo rabbit hearts in slack and contractured states, approximating diastolic and systolic conditions. The data were analysed with a suite of methods that focused on different aspects of the myocardium. In the slack heart, we observed a similar transmural gradient in helix angle of the primary eigenvector of up to 23.6°/mm in the left ventricle and 24.2°/mm in the right ventricle. In the contractured heart, the same transmural gradient remained largely linear, but was offset by up to +49.9° in the left ventricle. In the right ventricle, there was an increase in the transmural gradient to 31.2°/mm and an offset of up to +39.0°. The application of tractography based on each eigenvector enabled visualisation of streamlines that depict cardiomyocyte and sheetlet organisation over large distances. We observed multiple V- and N-shaped sheetlet arrangements throughout the myocardium, and insertion of sheetlets at the intersection of the left and right ventricle. This study integrates several complementary techniques to visualise and quantify the heart's microstructure, projecting parameter representations across different length scales. This represents a step towards a more comprehensive characterisation of myocardial microstructure at the whole organ level.
Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom.
Irvin
I
Teh
Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
Rebecca A B
RA
Burton
Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom.
Darryl
D
McClymont
Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
Rebecca A
RA
Capel
Department of Pharmacology, University of Oxford, Oxford, United Kingdom.
Daniel
D
Aston
National Heart and Lung Institute, Imperial College London, London, United Kingdom; Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg - Bad Krozingen, Medical School of the University of Freiburg, Germany.
Peter
P
Kohl
Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom. Electronic address: jurgen.schneider@cardiov.ox.ac.uk.
Jürgen E
JE
Schneider
D000818:Animals; D001696:Biomechanical Phenomena; D003971:Diastole; D056324:Diffusion Tensor Imaging; D006321:Heart / Q000502:physiology*; D006801:Humans; D008297:Male; D055595:Mechanical Phenomena; D009206:Myocardium / Q000166:cytology*; D011817:Rabbits; D013599:Systole
Diastole; Diffusion tensor imaging; Myocardial tissue characterisation; Rabbit heart; Systole; Tractography