Pressure and tone dependence of coronary diastolic input impedance and capacitance

Abstract

To quantify reactive elements of the coronary circulation, we have characterized in vivo diastolic coronary input impedance by introducing sinusoidal pressure oscillations of constant amplitude and varying frequency at constant mean pressure levels during prolonged diastoles in heart-blocked dogs anesthetized with pentobarbital. The behavior of coronary input impedance is similar to that observed in other peripheral vascular beds and is a function of both mean distending pressure and vasomotor tone. The behavior of impedance modulus and phase at each pressure level could be described by a lumped resistive-capacitive (RC) parallel model over a frequency range of 1-5 Hz. At higher frequencies the phase angle response could be characterized by adding a Voigt viscoelastic element to the original RC model. Calculated coronary capacitances for both models were similar in magnitude and varied inversely with mean coronary distending pressure. Values for the RC and RC viscoelastic model in the maximally dilated coronary bed were 14.1 and 21.6 X 10(-3) ml X mmHg X 100 g-1 at 30 mmHg and 2.65 and 2.70 X 10(-3) ml X mmHg-1 X 100 g-1 at 110 mmHg. With vasomotor tone intact, calculated coronary capacitance at each pressure level was reduced by a factor of two. These results indicate that an RC parallel model with pressure- and vasomotor tone-dependent capacitance adequately describes diastolic coronary input impedance at frequencies encountered during ordinary diastoles. The addition of a viscoelastic element provides adequate fits up to frequencies of 10 Hz.

Model of the coronary circulation based on pressure dependence of coronary resistance and compliance

“…2,10,24,27,29). Because of this compliance, the volume of the micro-vessels will vary depending on the difference between luminal pressure and tissue pressure: transmural pressure.…”

Coronary structure and perfusion in health and disease

“…Moreover, all vessels are elastic and their diameters change as a function of the transmural pressure difference across the vascular wall (Spaan et al 2006). Despite these complicated interactions, linear system analysis is often applied and vascular compartments are described by simple resistances and compliances (Canty et al 1985;De Bruyne et al 1994). Since nonlinear systems behave linearly within a limited range of signal variations, these models may be successful in predicting pressure and flow variations, but the estimated parameters from such models rarely bear a direct relationship to biophysical properties.…”

Epicardial Coronary Capacitive Blood Flow

“…For RC model with normal vascular tone, a = 0.0173, b = 0.02203; for RC model with vasodilation, a = 0.02318, b = 0.02403; for RC viscoelastic model with normal vascular tone, a = 0.03103, b = 0.02485; and for RC viscoelastic model with vasodilation, a = 0.05346, b = 0.02891. The capacitance is calculated for 100 g myocardium, while in the simulation, a was multiplied by 0.4 because the LADsupplied myocardium was assumed to be 40 g. The value of the viscoelastic coefficient K under different perfusion Canty (1985) as an exponential function of the perfusion pressure.…”

“…† To whom correspondence should be addressed at Cardiovascular Engineering Laboratory, Department of Biomedical Engineering, 617 Bowser Road, Piscataway, New Jersey 08854-8014. E-mail: jli@biomed.rutgers.edu occluding some portion of the coronary system (Eng and Kirk, 1983;Spaan, 1981), perfusion pressure perturbation and model-based system identification (Canty et al, 1985(Canty et al, , 1987Judd et al, 1991a;van Huis et al, 1987), and measurement of pressure wavefront velocity (Arts and Reneman, 1985). While these methods provide insights about the elastic property of the coronary vessels, they cannot be applied safely in clinical environment.…”