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Coronary oscillatory flow amplitude is more affected by perfusion pressure than ventricular pressure
R Krams1, P Sipkema, N Westerhof
1Laboratory for Physiology, Free University, Amsterdam, The Netherlands.
Insights
This study reveals that coronary blood flow changes are significantly influenced by perfusion pressure, not just left ventricular pressure. Time-varying elastance best explains these findings in cat hearts.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
Background:
- Cardiac contraction affects coronary blood flow.
- Understanding the relationship between left ventricular pressure and coronary flow is crucial.
Purpose of the Study:
- Investigate the relationship between left ventricular developed pressure (delta Piv) and coronary oscillatory flow amplitude (delta F).
- Examine these relationships at varying constant perfusion pressures (Pp).
- Test the hypothesis that changing elastic properties of cardiac muscle influence phasic coronary flow.
Main Methods:
- Utilized an isolated, blood-perfused cat heart model.
- Maintained constant perfusion pressure (Pp) levels.
- Measured left ventricular developed pressure (delta Piv) and coronary oscillatory flow amplitude (delta F).
Main Results:
- At a perfusion pressure of 10 kPa, delta F was significantly related to delta Piv (delta F = (4.71 +/- 3.08).delta Piv + 337 +/- 75).
- At a constant delta Piv of 10 kPa, delta F was significantly related to perfusion pressure (delta F = 51.Pp + 211).
- The observed relationships were best predicted by the time-varying elastance concept.
Conclusions:
- Perfusion pressure has a considerable effect on coronary oscillatory flow amplitude.
- Left ventricular pressure has a smaller effect on coronary oscillatory flow amplitude.
- The time-varying elastance model effectively explains the observed hemodynamic relationships in the coronary circulation.
Abstract:
In this study on the isolated, maximally vasodilated, blood-perfused cat heart we investigated the relation between left ventricular developed pressure (delta Piv) and coronary oscillatory flow amplitude (diastolic minus systolic flow, delta F) at different levels of constant perfusion pressure (Pp). We hypothesized that the effect of cardiac contraction on the phasic flow results from the changing elastic properties of cardiac muscle. The coronary vessel compartment can, as can the left ventricular lumen compartment, be described by a time-varying elastance. This concept predicts that the effect of left ventricular pressure on delta F is small, whereas the effect of Pp is considerable. Both the waterfall model and the intramyocardial pump model predict the inverse. The relation between delta Piv and delta F at a Pp of 10 kPa is delta F = (4.71 +/- 3.08).delta Piv + 337 +/- 75 (slope in ml.min-1.100 g-1.kPa-1 and intercept in ml.min-1.100 g-1; n = 7); the relation between (constant levels of) Pp and delta F at a constant delta Piv of 10 kPa is delta F = 51.Pp + 211 (slope in ml.min-1.100 g-1.kPa-1 and intercept in ml.min-1.100 g-1; n = 6). The differences in slope are best predicted by the time-varying elastance concept.