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24 1 Biomechanics
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2
K ¼ λ þ
μ ð1:12Þ
3
known as the bulk modulus. The bulk modulus is a measure of the compressibility of
the solid. For an incompressible material, K and hence λ are unbounded (!1). If a
hydrostatic pressure is to be accompanied by a volume decrease, then the bulk
modulus K must be positive. Since shearing should occur in the direction of the
shearing stress, the following constrains holds for the parameters:
1 λ þ
2
μ
> 0, 1 > μ > 0 ð1:13aÞ
3
The corresponding bounds on E and v are given by:
0 < E 3μ, 1 < v
1
2
ð1:13bÞ
Hence, a simple tension is always accompanied by an extension. On the other hand,
in a direction normal to the direction of this tension, a contraction may take place.
Appendix 3: Equations for Fluids and Solids
The governing equations for the fluid domain are the Navier–Stokes (NS) and
continuity equations (Fefferman, 2000):
!
!
∂ V
∂t
þ V
∇!V!þ
∇!p
ρ
∇! V!¼ 0
where V is fluid velocity, P is fluid pressure, ρ is fluid mass density, η is fluid
dynamic viscosity, ∇
!
is the gradient operator, and D is the fluid rate of deformation
tensor.
The governing equations for the solid are the momentum and equilibrium equations (Fung, 1997):
2
η
ρ
!
∇
!
D ¼ 0
s
where
Ω(t) is the structural domain at time t, t1is surface traction vector, σijis stress
of the solid, and a
ρa
σ
i
σ
ijnj
is the acceleration of the material point along the ith direction.
i
ρfi¼ 0insΩ tðÞ
ij, j
ti¼ 0on
s
Γ tðÞ
References 25
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References
Bao, X., Lu, C., & Frangos, J. A. (2001). Mechanism of temporal gradients in shear-induced ERK1/
2 activation and proliferation in endothelial cells. American Journal of Physiology-Heart and
Circulatory Physiology, 281, H22–H29. https://doi.org/10.1152/ajpheart.2001.281.1.H22
Bathe, K. J. (1995). Finite element procedures. Englewood Cliffs: Prentice-Hall.
Bergel, D. H. (1972). In Y. C. Fung, N. Perrone, & M. Anliker (Eds.), Biomechanics: Its
foundations and objectives (pp. 105–138). Englewood Cliffs, NJ: Prentice- Hall.
Berger, S. A., & Jou, L. D. (2002). Flows in stenotic vessels. Annual Review of Fluid Mechanics,
32, 347–382. https://doi.org/10.1146/annurev.fluid.32.1.347
Buchanan, J. R., Jr., Kleinstreuer, C., Truskey, G. A., & Lei, M. (1999). Relation between
non-uniform hemodynamics and sites of altered permeability and lesion growth at the rabbit
aorto-celiac junction. Atherosclerosis, 143,27–40. https://doi.org/10.1016/S0021-9150(98)
00264-0
Chen, H., & Kassab, G. S. (2016). Microstructure-based biomechanics of coronary arteries in health
and disease. Journal of Biomechanics, 49(12), 2548–2559. https://doi.org/10.1016/j.jbiomech.
2016.03.023
Chen, H., Liu, Y., Zhao, X., Lanir, Y., & Kassab, G. S. (2011). A micromechanics finite-strain
constitutive model of fibrous tissue. Journal of the Mechanics and Physics of Solids, 59,
1823–1837. https://doi.org/10.1016/j.jmps.2011.05.012
Chen, H., Luo, T., Zhao, X., Lu, X., Huo, Y., & Kassab, G. S. (2013). Microstructural constitutive
model of active coronary artery media. Biomaterials, 34(31), 7575–7583. https://doi.org/10.
1016/j.biomaterials.2013.06.035
Chen, H., Zhao, X., Lu, X., & Kassab, G. S. (2013). Nonlinear micromechanics of soft tissue.
International Joural of Non-linear Mechanics, 56,79–85. https://doi.org/10.1016/j.
ijnonlinmec.2013.03.002
Chorin, A. J. (1968). Numerical solution of the Navier-Stokes equations. Mathematics of Compu-
tation, 22, 745–762. https://doi.org/10.1090/S0025-5718-1968-0242392-2
Chorin, A. J. (1969). On the convergence of discrete approximations to the Navier-Stokes equa-
tions. Mathematics of Computations, 23, 341–353. https://doi.org/10.2307/2004428
DeBakey, M. E., Lawrie, G. M., & Glaeser, D. H. (1985). Patterns of atherosclerosis and their
surgical significance. Annals of Surgery, 201(2), 115–131. https://doi.org/10.1097/00000658-
198502000-00001
Dobrin, P. B. (1978). Mechanical properties of arteries. Physiological Reviews, 58, 397–460.
https://doi.org/10.1152/physrev.1978.58.2.397
Donea, J., Giuliani, S., & Halleux, J. P. (1982). An arbitrary Lagrangian Eulerian fi
method for transient dynamic fluid structure interactions. Computer Methods in Applied
Mechanics and Engineering, 33, 689–723. https://doi.org/10.1016/0045-7825(82)90128-1
Douglas, J. E., & Greenfield, J. C. (1970). Epicardial coronary artery compliance in the dog.
Circulation Research, 27, 921–929. https://doi.org/10.1161/01.RES.27.6.921
Farmakis, T. M., Soulis, J. V., Giannoglou, G. D., Zioupos, G. J., & Louridas, G. E. (2004). Wall
shear stress gradient topography in the normal left coronary arterial tree: Possible implications
for atherogenesis. Current Medical Research and Opinion, 20(5), 587–596. https://doi.org/10.
1185/030079904125003340
Fefferman, C. L. (2000). Existence and smoothness of the Navier–Stokes equation. Princeton, NJ:
Princeton University.
Formaggia, L., & Nobile, F. (1999). A stability analysis for the arbitrary Lagrangian Eulerian
formulation with finite elements. East-West Journal of Numerical Mathematics, 7, 105–131.
Fung, Y. C. (1983). What principle governs the stress distribution in living organs? In Y. C. Fung,
E. Fukada, & J. Wang (Eds.), Biomechanics in China, Japan and USA (pp. 1–13). Beijing,
China: Science.
Fung, Y. C. (1990). Biomechanics: Motion, flow, stress and growth. New York: Springer.
nite element
26 1 Biomechanics
https://t.me/med1917
Fung, Y. C. (1993). Biomechanics: Mechanical properties of living tissues (2nd ed.). New York:
Springer.
Fung, Y. C. (1994). A first course in continuum mechanics (3rd ed.). Englewood Cliffs, NJ: Prentice
Hall.
Fung, Y. C. (1997). Biomechanics: Circulation. New York: Springer.
Giezeman, M. J., VanBavel, E., Grimbergen, C. A., & Spaan, J. A. (1994). Compliance of isolated
porcine coronary small arteries and coronary pressure-flow relations. American Journal of
Physiology-Heart and Circulatory Physiology, 36, H1190–H1198. https://doi.org/10.1152/
ajpheart.1994.267.3.H1190
Glowinski, R., Pan, T. W., Hesla, T. I., Joseph, D. D., & Periaux, J. (2001). A fictitious domain
approach to the direct numerical simulation of incompressible viscous flow past moving rigid
bodies: Application to particulate flow. Journal of Computational Physics, 169(2), 363–426.
https://doi.org/10.1006/jcph.2000.6542
Glowinski, R., Pan, T. W., & Periaux, J. (1994). A fictitious domain method for Dirichlet problem
and applications. Computer Methods in Applied Mechanics and Engineering, 111(3–4),
283–303. https://doi.org/10.1016/0045-7825(94)90135-X
Green, A. E., & Adkins, J. E. (1960). Large deformations and nonlinear continuum mechanics.
Oxford: Oxford University Press.
Gregersen, H., & Kassab, G. S. (1996). Biomechanics of the gastrointestinal tract.
Neurogastroenterology & Motility, 8, 277–297. https://doi.org/10.1111/j.1365-2982.1996.
tb00267.x
Gregg, D. E., Green, H. D., & Wiggers, C. J. (1935). Phasic variations in peripheral coronary
resistance and their determinants. American Journal of Physiology, 112, 362–373. https://doi.
org/10.1152/ajplegacy.1935.112.2.362
Guccione, J. M., Kassab, G., & Ratcliffe, M. (Eds.). (2010). Computational cardiovascular
mechanics: Modeling and applications in heart failure. New York: Springer.
He, X., & Ku, D. N. (1996). Pulsatile flow in the human left coronary artery bifurcation: Average
conditions. Journal of Biomechanical Engineering, 118,74–82. https://doi.org/10.1115/1.
2795948
Hughes, T. J. R., Liu, W. K., & Zimmermann, T. K. (1981). Lagrangian Eulerian finite element
formulation in incompressible viscous flows. Computer Methods in Applied Mechanics and
Engineering, 29, 329–349. https://doi.org/10.1016/0045-7825(81)90049-9
Kassab, G. S. (2001). Analysis of coronary circulation: A bioengineering approach. In Y. C. Fung
(Ed.), Introduction to bioengineering (pp. 93–105). Singapore: World Scienti
Kleinstreuer, C., Hyun, S., Buchanan, J. J. R., Longest, P. W., Archie, J. P., Jr., & Truskey, G. A.
(2001). Hemodynamic parameters and early intimal thickening in branching blood vessels.
Critical Reviews in Biomedical Engineering, 29,1–64. https://doi.org/10.1615/
CritRevBiomedEng.v29.i1.10
Kovacs, S. J., McQueen, D. M., & Peskin, C. S. (2001). Modelling cardiac fluid dynamics and
diastolic function. Philosophical Transactions of the Royal Society of London Series
A-Mathematical Physical and Engineering Sciences, 359(1783), 1299–1314. https://doi.org/
10.1098/rsta.2001.0832
Ku, D. N. (1997). Blood flow in arteries. Annual Review of Fluid Mechanics, 29, 399–434. https://
doi.org/10.1146/annurev.fluid.29.1.399
Kuo, L., Chilian, W. M., & Davis, M. J. (1991). Interaction of pressue- and flow-induced responses
in porcine coronary resistance vessels. American Journal of Physiology, 261, H1706–H1715.
https://doi.org/10.1152/ajpheart.1991.261.6.H1706
Kuo, L., Davis, M. J., & Chilian, W. M. (1988). Myogenic activity in isolated subepicardial and
subendocardial coronary arterioles. American Journal of Physiology, 255, H1558–H1562.
https://doi.org/10.1152/ajpheart.1988.255.6.H1558
Lei, M., Kleinstreuer, C., & Truskey, G. A. (1996). A focal stress gradient-dependent mass transfer
mechanism for atherogenesis in branching arteries. Medical Engineering & Physics, 18(4),
326–332. https://doi.org/10.1016/1350-4533(95)00045-3
fic.
References 27
https://t.me/med1917
Manor, D., Beyar, R., Shofti, R., & Sideman, S. (1994). In-vivo study of the mechanical properties
of epicardial coronary arteries. Journal of Biomechanical Engineering, 116, 131–132. https://
doi.org/10.1115/1.2895697
McQueen, D. M., & Peskin, C. S. (1983). Computer-assisted design of pivoting-disc prosthetic
mitral valves. The Journal of Thoracic and Cardiovascular Surgery, 86, 126–135.
McQueen, D. M., & Peskin, C. S. (1985). Computer-assisted design of butterfly bileaflet valves for
the mitral position. Scandinavian Journal of Thoracic and Cardiovascular Surgery, 19,
139–148. https://doi.org/10.3109/14017438509102709
McQueen, D. M., & Peskin, C. S. (2000). A three-dimensional computer model of the human heart
for studying cardiac fluid dynamics. Computer & Graphics, 34(1), 56–60. https://doi.org/10.
1145/563788.604453
McQueen, D. M., Peskin, C. S., & Yellin, E. L. (1982). Fluid dynamics of the mitral valve:
Physiological aspects of a mathematical model. American Journal of Physiology, 242,
H1095–H1110. https://doi.org/10.1152/ajpheart.1982.242.6.H1095
Nakayama, K., Osol, G., & Halpern, W. (1988). Reactivity of isolated porcine coronary resistance
arteries to cholinergic and adrenergic drugs and transmural pressure changes. Circulation
Research, 62, 741–748.
Patankar, S. V. (1980). Numerical heat transfer and fluid flow. New York: Hemisphere Publishing
Corporation.
Patel, D. J., & Janicki, J. S. (1970). Static elastic properties of the left coronary circumflex artery and
the common carotid artery in dogs. Circulation Research, 2, 149–158. https://doi.org/10.1161/
01.RES.27.2.149
Perktold, K., Resch, M., & Florian, H. (1991). Pulsatile non-Newtonian flow characteristics in a
three-dimensional human carotid bifurcation model. Journal of Biomechanical Engineering,
113, 464–475. https://doi.org/10.1115/1.2895428
Perktold, K., Resch, M., & Peter, R. O. (1991). Three dimensional numerical analysis of pulsatile
flow and wall shear stress in the carotid artery bifurcation. Journal of Biomechanics, 24,
409–420. https://doi.org/10.1016/0021-9290(91)90029-M
Peskin, C. S. (1972). Flow patterns around heart valves: A digital computer method for solving the
equations of motion. (Ph.D.), Albert Einstein College of Medicine, Univ. Microfilms.
Peskin, C. S. (1977). Flow patterns around heart valves: A numerical method. Journal of Compu-
tational Physics, 25, 220–252. https://doi.org/10.1016/0021-9991(77)90100-0
Peskin, C. S. (2002). The immersed boundary method. Acta Numerica, 11, 479–517. https://doi.
org/10.1017/S0962492902000077
Peskin, C. S., & McQueen, D. M. (1993). Computational biofluid dynamics. In A. Y. Cheer & C. P.
van Dam (Eds.), Fluid dynamics in biology (Vol. 141, pp. 161–186). Oxford: Oxford University
Press.
Ramaswamy, S. D., Vigmostad, S. C., Wahle, A., Lia, Y. G., Olszewski, M. E., Braddy, K. C., ...
Chandran, K. B. (2004). Fluid dynamics in a human left anterior descending coronary artery
with arterial motion. Annals of Biomedical Engineering, 32, 1628–1641. https://doi.org/10.
1007/s10439-004-7816-3
Reneman, R. S., & Arts, T. (1985). Dynamic capacitance of epicardial coronary arteries in vivo.
Journal of Biomechanical Engineering, 107,29–33. https://doi.org/10.1115/1.3138515
Sankaranarayanan, M., Ghista, D. N., Poh, C. L., Seng, T. Y., & Kassab, G. S. (2006). Analysis of
blood flow in an out-of-plane CABG model. American Journal of Physiology-Heart and
Circulatory Physiology, 291, H283–H295. https://doi.org/10.1152/ajpheart.01347.2005
Santamarina, A., Weydahl, E., Sigel, J. M., & Moore, J. S. (1998). Computational analysis of flow
in a curved tube model of the coronary arteries: Effects of time-varying curvature. Annals of
Biomedical Engineering, 26, 944–954. https://doi.org/10.1114/1.113
Singer, C. (1959). A short history of scientific ideas to 1900. New York: Oxford University Press.
Spaan, J. A. E. (1985). Coronary diastolic pressure-flow relation and zero-flow pressure explained
on the basis of intramyocardial compliance. Circulation Research, 56(3), 293–309. https://doi.
org/10.1161/01.RES.56.3.293
28 1 Biomechanics
https://t.me/med1917
Stroud, J. S., Berger, S. A., & Saloner, D. (2002). Numerical analysis of flow through a severely
stenotic carotid artery bifurcation. Journal of Biomechanical Engineering, 124,9–20. https://
doi.org/10.1115/1.1427042
Taylor, C. A., Hughes, T. J. R., & Zarins, C. K. (1998). Finite element modeling of three-
dimensional pulsatile flow in the abdominal aorta: Relevance to atherosclerosis. Annals of
Biomedical Engineering, 26, 975–987. https://doi.org/10.1114/1.140
Tomoike, H., Ootsubo, H., Sakai, K., Kikuchi, Y., & Nakamura, M. (1981). Continuous measure-
ment of coronary artery diameter in situ. American Journal of Physiology-Heart and Circula-
tory Physiology, 240, H73–H79. https://doi.org/10.1152/ajpheart.1981.240.1.H73
Vigmond, E. J., Clements, C., McQueen, D. M., & Peskin, C. S. (2008). Effect of bundle branch
block on cardiac output: A whole heart simulation study. Progress in biophysics & molecular
biology, 97(2–3), 520–542. https://doi.org/10.1016/j.pbiomolbio.2008.02.022
Weydahl, E. S., & Moore, J. E. (2001). Dynamic curvature strongly affects wall shear rates in a
coronary artery bifurcation model. Journal of Biomechanics, 34, 1189–1196. https://doi.org/10.
1016/S0021-9290(01)00051-3
Zeng, D., Ding, Z., Friedman, M. H., & Ethier, C. R. (2003). Effect of cardiac motion on right
coronary artery hemodynamics. Annals of Biomedical Engineering, 31, 420–429. https://doi.
org/10.1114/1.1560631
Zhang, W., Chen, H. Y., & Kassab, G. S. (2007). A novel rate insensitive linear viscoelastic model
for soft tissues. Biomaterials, 28(24), 3579–3586. https://doi.org/10.1016/j.biomaterials.2007.
04.040
Chapter 2
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Morphometry of Coronary Vasculature
2.1 Introduction
The morphological (i.e., geometric) features (e.g., diameter, length, vessel wall
thickness, branching pattern) of the coronary vasculature (i.e., arteries, capillaries,
and veins) are necessary to understand the circulation, to predict the pressure–flow
relationship, to determine the longitudinal pressure and flow distribution, to understand the distensibility of the blood vessels, to study atherogenesis or restenosis, and
to determine the effect of hypertension, hypertrophy, flow-overload, and tissue
remodeling on the coronary circulation. This is analogous to the need to know the
structure of the circuitry as well as the distribution of the resistors, capacitors, and
inductors in an electric circuit if one wishes to analyze an electric instrument. Trying
to understand the coronary circulation without the morphometric data is like exploring a continent without a map. Specifically, in a netw ork analysis of coronary blood
flow, the circuit must agree with the anatomical data on the branching pattern and
geometry of the coronary vasculature, and the basic hemodynamic equations and
boundary conditions must be satisfied.
In this chapter, we provide a quantitative overview of the morphometry of the
entire coronary vasculature including the geometry and branching pattern of coronary vasculature, 3D coronary reconstruction, image-based segmentation and extraction, and grid generation. We shall employ the reductionist approach to reduce the
coronary vasculature into measurable vessel segments and subsequently use the
integrationist approach to reconstruct the entire coronary vasculature. The chapter
also describes the evolution of the automated process of reconstruction of the
coronary vasculature, which results in significant time savings and translates to
creation of patient-specific models of the coronary arteries which can be used to
Electronic supplementary material The online version of this chapter (https://doi.org/10.1007/
978-3-030-14819-5_2) contains supplementary material, which is available to authorized users.
© Springer Science+Business Media, LLC, part of Springer Nature 2019
G. S. Kassab, Coronary Circulation, https://doi.org/10.1007/978-3-030-14819-5_2
29
30 2 Morphometry of Coronary Vasculature
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Fig. 2.1 Schematic
illustration of major
coronary arteries on the
surface of the heart
Right
Coronary
Artery
Aorta
Left Coronary
Artery
Circumflex
Artery
Left
Anterior
Descending
Artery
model disease, aid in diagnosis, and advance the implementation of therapeutic
interventions.
2.2 Coronary Vasculature
The heart muscle is nourished by a complex system of blood vessels that make up the
coronary circulation. The function of the coronary circulation is to continually
supply blood to meet the metabolic requirements of cardiac tissue that is critical to
the health of the heart. The coronary arterial system consists of large epicardial
coronary arteries that span the surface of the heart and give rise to intramyocardial
coronary arteries that penetrate the inner layers of the heart. The branching pattern of
the coronary arterial tree is rather complex and gives rise to millions of capillary
blood vessels that nourish the myocardium.
The epicardial coronary arteries consist of the right coronary artery (RCA) and
the left common coronary artery (LCCA) which bifurcates into the left anterior
descending (LAD) artery and left circumflex (LCx) artery (Fig. 2.1). The RCA gives
rise to several right ventricular and atrial branches that perfuse the right ventricle and
atrium, respectively. The distal portion of the RCA becomes the posterior
descending artery which supplies the posterior septum and a portion of the left
ventricle (LV). The LCx artery largely supplies the LV while the LAD artery
supplies the anterior LV and septum. The large arteries branch into smaller arteries
and eventually connect to the capillaries.
There are two routes by which the capillary flow returns to the heart via the
coronary venous circulation. In one route, blood flows from the great cardia c vein to
2.3 Reduction of Coronary Vasculature 31
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the posterior vein of the LV, to the posterior interventricular vein, to the oblique vein
of Marshal, to the anterior cardiac vein, and into the coronary sinus on the epicardial
surface and finally empties into the right atrium. In another route, blood flows
through the smallest cardiac veins of Thebesius to the endocardial surface and drains
directly into the heart chambers (predominantly into the right ventricle). The
Thebesian venous system is relatively small in volume as compared to the coronary
sinusal venous system (Kassab, Lin, & Fung, 1994b).
2.3 Reduction of Coronary Vasculature
There is signifi cant variability in the coronary anatomy at the level of large epicardial
sub-networks both “globally” at the level of the heart (left or right dominance where
either the left or right coronary artery perfuses the majority of myocardium, respectively) as well as “locally” at the level of bifurcations (Bruschke & Buis, 1987;
Zamir, 1990). The vessels are characterized by highly irregular and asymmetric
branching patterns (Kaimovitz, Huo, Lanir, & Kassab, 2008; Kalsho & Kassab,
2004). Due to the fractal nature of the coronary vasculature (Zamir, 1999, 2001), the
number of vessels increases in a geometric fashion towards the capillary vessels.
This leads to an overwhelming number of vessels which preclude a deterministic
description of the coronary anatomy beyond the epicardial vessels which can be
made subject specific. For these reasons, a statistical representation of the anatomy is
necessary to facilitate a reconstruction of the entire coronary vasculature.
The reduction–integration approach will be used to first dissect the coronary
vasculature to quantify the geometry of individual vessels (this section), followed
by a mathematical reconstruction to integrate the system ranging from the major
coronary arteries to the major veins with all vessels in between (next section). There
are several differences between the coronary arteries compared to veins. The
branching pattern of the coronary arteries is largely tree-like with few collaterals in
the swine model which is similar to health humans (Kassab, Rider, Tang, & Fung,
1993; Weaver, Pantely, Bristow, & Ladley, 1986). The venous system, on the other
hand, has significant intra- and inter-venous connections (Kassab et al., 1994b). In
diastole, the cross section of a coronary artery or arteriole is circular, while that of
veins and venules is approximately elliptical (Kassab et al., 1993, 1994b). A very
detailed description of the features of the geometry (morphometry) of the porcine
coronary vasculature was quantitatively characterized based on a vessel ordering
scheme (Kassab, Berkley, & Fung, 1997; Kassab et al., 1993, 1994b ; Kassab &
Fung, 1994) described below. Kassab (2000) reviewed the methodologies used to
dissect the entire coronary vasculature to quantify its morphometry. The methodology utilized to describe the morphology of the porcine coronary vasculature is
briefly outlined below.
32 2 Morphometry of Coronary Vasculature
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2.3.1 Casting Material
The silicone elastomer (GE Compound 88017) casting method, now widely used for
studying intravascular anatomy and geometry, was developed by So bin and colleagues (Sobin, 1965; Sobin, Tremer, & Frasher, 1964). The catalyzed elastomer is
initially a liquid which solidifies over time. The rate of increase in viscosity is
determined by the concentration of catalyst used (Fung, Sobin, Tremer, Yen, &
Ho, 1983). A catalyst concentration of 6.0% stanneous 2-ethylhexoate and 3.0%
ethyl silicate leads to complete hardening of the material within 1 h. Silicone
elastomer has many desirable properties such as relatively low viscosity and surface
tension so that it can readily pass through the capillary bed, negligible volume
change on catalysis, non-exothermic controlled polymerization, does not extravasate, and is nontoxic (acutely) to the endothelium.
2.3.2 Animal and Isolated Heart Preparation
Some of the most extensive studies on the morphometry of porcine coronary
vasculature have been performed by Kassab and colleagues (see review in Kassab
(2000)). These studies were performed on healthy young farm pigs of either sex
(Kassab et al., 1993). In these studies, the heart was exposed, the animal was
heparinized to prevent coagulation of blood and the heart was KCl arrested to obtain
a relaxed state of the myocardium. The heart was then excised with the ascending
aorta clamped to keep air bubbles out of the coronary arteries. The RCA, LAD, and
LCx arteries were cannulated under cold (0
A cardioplegic solution containing BDM (2,3-butanedione monoxime) and adenosine was used to perfuse the coronary vessels to maintain the myoca rdium in a
relaxed state and the vasculature in a dilated state, respectively (Kassab et al., 1993).
C) saline to avoid air bubbles (Fig. 2.2).
2.3.3 Polymer Cast of Coronary Vasculature
A freshly catalyzed and well-stirred elastomer solution was degassed under a
vacuum to remove air bubbles formed by stirring. The degassed elastomer was
then perfused through the coronary arteries. The perfusion pressure was set initially
at 130 mmHg for 5 min and then lowered and maintained at 80 mmHg until the
elastomer was hardened, in approximately 1 h (Fig. 2.2). The heart was then
refrigerated in saline for several days to increase the strength of the silicone rubber
in preparation for the histological and cast studies of coronary vasculature.
2.3 Reduction of Coronary Vasculature 33
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Fig. 2.2 Schematic
illustration of elastomer
perfusion apparatus and
isolated heart preparation.
Reproduced from Kassab
et al. (1993) with permission
2.3.4 Histological and Cast Specimens
The morphometric data on the coronary microvessels (arterioles, capillaries, and
venules) of diameters <40 μm was obtained from histological specimens (Kassab
et al., 1993, 1994b). To obtain this data, plugs of myocardial tissue were removed
from the left ventricles (LV) and right ventricles (RV) of cast hearts. Each plug
(approximately 5 5mm wall thickness) was mounted on a freezing microtome,
and serial sections of 60–80 μm thickness were cut. Each section was dehydrated
with 100% alcohol and cleared with methyl salicylate to render the myocardium
transparent and the elastomer-filled microvasculature visible in light microscopy.
Figure 2. 3a shows an example of a histological section from the LV of a porcine
heart showing coronary microvessels.
The morphometric data on the coronary arterial and venous vessels of diameters
>40 μm was obtained from cast studies. The cast heart, after removing several plugs
as described above, was corroded with a 30% KOH solution for several days. The
coronary venous system was pruned away leaving the major coronary arteries (RCA,
LAD, and LCx arteries) with clusters of capillaries. Separate hearts were used to
obtain casts of the coronary veins (coronary sinus and Thebesian veins) by pruning
away the arteries. Figure 2.3b shows an example of a cast of LAD artery of porcine
heart.
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