title: Myocardial Perfusion: Characteristics of Distal Intramyocardial Arteriolar Trees.
abstract: A combination of experimental, theoretical, and imaging methodologies is used to examine the hierarchical structure and function of intramyocardial arteriolar trees in porcine hearts to provide a window onto a region of myocardial microvasculature which has been difficult to fully explore so far. A total of 66 microvascular trees from 6 isolated myocardial specimens were analyzed, with a cumulative number of 2438 arteriolar branches greater than or equal to 40 μm lumen diameter. The distribution of flow rates within each tree was derived from an assumed power law relationship for that tree between the diameter of vessel segments and flow rates that are consistent with that power law and subject to conservation of mass along hierarchical structure of the tree. The results indicate that the power law index increases at levels of arteriolar vasculature closer to the capillary level, consistent with a concomitant decrease in shear stress acting on endothelial tissue. These results resolve a long standing predicament which could not be resolved previously because of lack of data about the 3D, interconnected, arterioles. In the context of myocardial perfusion, the results indicate that the coefficient of variation of flow rate in pre-capillary distal arterioles is high, suggesting that heterogeneity of flow rate in these arterioles is not entirely random but may be due at least in part to active control.
authors.affiliation: Departments of Applied Mathematics and of Medical Biophysics, Western University, 1151 Richmond Street, London, ON, N6A 5B7, Canada.
authors.forename: Mair
authors.initials: M
authors.lastname: Zamir
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Vercnocke
authors.affiliation: Biomedical Imaging Resource, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA.
authors.forename: Phillip K
authors.initials: PK
authors.lastname: Edwards
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA.
authors.forename: Jill L
authors.initials: JL
authors.lastname: Anderson
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA.
authors.forename: Steven M
authors.initials: SM
authors.lastname: Jorgensen
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic College of Medicine, 200 First Street S.W., Rochester, MN, 55905, USA. elran@mayo.edu.
authors.forename: Erik L
authors.initials: EL
authors.lastname: Ritman
mesh_terms: D000818:Animals; D001160:Arterioles / Q000502:physiology*; D003326:Coronary Circulation / Q000502:physiology*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000502:physiology; D006321:Heart / Q000000981:diagnostic imaging / Q000502:physiology*; D055806:Microvessels / Q000000981:diagnostic imaging / Q000502:physiology; D009206:Myocardium; D013552:Swine; D055114:X-Ray Microtomography
keywords: Cube law; Microvasculature; Murray’s law; Pre-capillary arterioles; Shear stress