Identification of canine coronary resistance and intramyocardial compliance on the basis of the waterfall model
- 196 Downloads
This study was performed to elucidate the effects of cardiac contraction on coronary pressure-flow relations. On the basis of the waterfall mechanism, a lumped model of the coronary arterial system is presented consisting of a proximal (epicardial) compliance, a coronary resistance, and an intramyocardial compliance. A “back”-pressure, assumed to be proportional (constant k) to left ventricular pressure, impedes flow. From steady-state measurements of circumflex coronary artery flow and inflow pressure, together with left ventricular pressure, the values of the three model parameters and the constant k have been estimated. In the control condition proximal compliance is found to be 1.7×10−12 m4s2kg−1, intramyocardial compliance 110×10−12m4s2kg−1, and resistance 7.5×109kgm−4s−1. The proportionality constant k is close to unity. Effects of changes in left ventricular pressure and inflow pressure and the effect of vasoactive drugs on the parameters are also investigated. Changes in coronary resistance are always opposite to changes in intramyocardial compliance. Sensitivity analysis showed that epicardial compliance plays its major role during isovolumic contraction and relaxation; resistance plays a role throughout the cardiac cycle but is more important in diastole than in systole, whereas intramyocardial compliance plays a role in systole and in early diastole.
KeywordsWaterfall Intramyocardial compliance Coronary resistance Coronary pressure-flow relation
Unable to display preview. Download preview PDF.
- 6.Canty, J.M., F.J. Klocke, and R.E. Mates. Coronary capacitance calculated from in vivo measurement of diastolic coronary input impedance.Fed. Proc. 40:1097, 1982.Google Scholar
- 7.Canty, J.M., R.E. Mates, and F.J. Klocke. Rapid determination of capacitance-free pressure-flow relationships during single diastoles.Fed. Proc. 42:1092, 1983.Google Scholar
- 8.Collatz, L.The Numerical Treatment of Differential Equations. Berlin: Springer-Verlag, 1966, pp. 78–97.Google Scholar
- 12.Downey, J.M. Comments on flow through collapsible tubes at low Reynolds numbers. Letter.Circ. Res. 48:299–301, 1981.Google Scholar
- 13.Eng, C. and E.S. Kirk. The arterial component of the coronary capacitance.Circulation 68(Suppl II): [Abstract 1232], 1983.Google Scholar
- 15.Johnson, J.R. and J.R. DiPalma. Intramyocardial pressure and its relation to aortic blood pressure.Am. J. Physiol. 125:234–243, 1939.Google Scholar
- 16.Kamm, R.D. and A.H. Shapiro. Unsteady flow in a collapsible tube subjected to external pressure or body forces.J. Fluid. Mech. 95:1–78, 1979.Google Scholar
- 22.Pedley, T.J.The Fluid Mechanics of Large Blood Vessels. Cambridge: Cambridge University Press, 1980, pp. 301–368.Google Scholar
- 24.Powell, M.J.D. An efficient method for finding the minimum of a function of several variables without calculating derivatives.Computer J. 65:735–740, 1964.Google Scholar
- 25.Rabiner, L.R. and B. Gold.Theory and Application of Digital Signal Processing. Englewood Cliffs N.J.: Prentice Hall, 1975, pp. 75–294.Google Scholar