Regional ventricular wall thickening reflects changes in cardiac fiber and sheet structure during contraction: quantification with diffusion tensor MRI. Export

@article{citeulike:904280, abstract = {Dynamic changes of myocardial fiber and sheet structure are key determinants of regional ventricular function. However, quantitative characterization of the contraction-related changes in fiber and sheet structure has not been reported. The objective of this study was to quantify cardiac fiber and sheet structure at selected phases of the cardiac cycle. Diffusion tensor MRI was performed on isolated, perfused Sprague-Dawley rat hearts arrested or fixed in three states as follows: 1) potassium arrested (PA), which represents end diastole; 2) barium-induced contracture with volume (BV+), which represents isovolumic contraction or early systole; and 3) barium-induced contracture without volume (BV-), which represents end systole. Myocardial fiber orientations at the base, midventricle, and apex were determined from the primary eigenvectors of the diffusion tensor. Sheet structure was determined from the secondary and tertiary eigenvectors at the same locations. We observed that the transmural distribution of the myofiber helix angle remained unchanged as contraction proceeded from PA to BV+, but endocardial and epicardial fibers became more longitudinally orientated in the BV- group. Although sheet structure exhibited significant regional variations, changes in sheet structure during myocardial contraction were relatively uniform across regions. The magnitude of the sheet angle, which is an index of local sheet slope, decreased by 23 and 44\% in BV+ and BV- groups, respectively, which suggests more radial orientation of the sheet. In summary, we have shown for the first time that geometric changes in both sheet and fiber orientation provide a substantial mechanism for radial wall thickening independent of active components due to myofiber shortening. Our results provide direct evidence that sheet reorientation is a primary determinant of myocardial wall thickening.}, address = {Cardiovascular Magnetic Resonance Laboratories, Department of Medicine, Washington University, St Louis, Missouri, USA.}, author = {Chen, J. and Liu, W. and Zhang, H. and Lacy, L. and Yang, X. and Song, S. K. and Wickline, S. A. and Yu, X.}, citeulike-article-id = {904280}, citeulike-linkout-0 = {http://dx.doi.org/10.1152/ajpheart.00041.2005}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/16219812}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=16219812}, doi = {10.1152/ajpheart.00041.2005}, issn = {0363-6135}, journal = {Am J Physiol Heart Circ Physiol}, keywords = {fiber, geometry}, month = {November}, number = {5}, posted-at = {2006-10-18 23:00:15}, priority = {5}, title = {Regional ventricular wall thickening reflects changes in cardiac fiber and sheet structure during contraction: quantification with diffusion tensor MRI.}, url = {http://dx.doi.org/10.1152/ajpheart.00041.2005}, volume = {289}, year = {2005} }

TY - JOUR ID - citeulike:904280 L3 - citeulike-article-id:904280 N2 - Dynamic changes of myocardial fiber and sheet structure are key determinants of regional ventricular function. However, quantitative characterization of the contraction-related changes in fiber and sheet structure has not been reported. The objective of this study was to quantify cardiac fiber and sheet structure at selected phases of the cardiac cycle. Diffusion tensor MRI was performed on isolated, perfused Sprague-Dawley rat hearts arrested or fixed in three states as follows: 1) potassium arrested (PA), which represents end diastole; 2) barium-induced contracture with volume (BV+), which represents isovolumic contraction or early systole; and 3) barium-induced contracture without volume (BV-), which represents end systole. Myocardial fiber orientations at the base, midventricle, and apex were determined from the primary eigenvectors of the diffusion tensor. Sheet structure was determined from the secondary and tertiary eigenvectors at the same locations. We observed that the transmural distribution of the myofiber helix angle remained unchanged as contraction proceeded from PA to BV+, but endocardial and epicardial fibers became more longitudinally orientated in the BV- group. Although sheet structure exhibited significant regional variations, changes in sheet structure during myocardial contraction were relatively uniform across regions. The magnitude of the sheet angle, which is an index of local sheet slope, decreased by 23 and 44% in BV+ and BV- groups, respectively, which suggests more radial orientation of the sheet. In summary, we have shown for the first time that geometric changes in both sheet and fiber orientation provide a substantial mechanism for radial wall thickening independent of active components due to myofiber shortening. Our results provide direct evidence that sheet reorientation is a primary determinant of myocardial wall thickening. IS - 5 JF - Am J Physiol Heart Circ Physiol SN - 0363-6135 AD - Cardiovascular Magnetic Resonance Laboratories, Department of Medicine, Washington University, St Louis, Missouri, USA. TI - Regional ventricular wall thickening reflects changes in cardiac fiber and sheet structure during contraction: quantification with diffusion tensor MRI. VL - 289 KW - fiber KW - geometry AU - Chen, J AU - Liu, W AU - Zhang, H AU - Lacy, L AU - Yang, X AU - Song, SK AU - Wickline, SA AU - Yu, X PY - 2005/11// UR - http://dx.doi.org/10.1152/ajpheart.00041.2005 ER -