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Effect of packed cell volume on diastolic coronary artery pressure-flow relations in the dog
F Kajiya1, K Tsujioka, Y Ogasawara
1Department of Medical Engineering, Kawasaki Medical School, Kurashiki, Japan.
Insights
Packed cell volume significantly influences coronary circulation dynamics. Higher packed cell volumes increase coronary artery pressure and resistance, impacting blood flow, while left ventricular pressures remain unaffected.
Area of Science:
- Cardiovascular Physiology
- Hemodynamics
- Biophysics
Background:
- Understanding coronary circulation is vital for cardiovascular health.
- Haemorheological properties, particularly packed cell volume, can affect blood flow dynamics.
- Minimal vasomotor tone in experimental models allows isolation of perfusate effects.
Purpose of the Study:
- To investigate the role of perfusate packed cell volume on coronary circulation.
- To analyze the diastolic pressure-flow relationship under varying packed cell volumes.
- To model coronary hemodynamics using an electrical analogue.
Main Methods:
- Studied diastolic pressure-flow relations in open-chest dogs using blood with varied packed cell volumes (12-67%).
- Developed an electrical analogue model (R1, C, R2, Pint) to analyze pressure-flow data.
- Measured stop-flow coronary artery pressure (Psf) after perfusion line clamping.
Main Results:
- Stop-flow coronary artery pressure (Psf) decreased with decreasing packed cell volume (r=0.45).
- Zero-flow pressure intercept correlated strongly with Psf (r=0.87).
- Total resistance (R1+R2) and distal resistance ratio (R2/(R1+R2)) decreased with lower packed cell volumes.
Conclusions:
- Packed cell volume is a key determinant of coronary circulation hemodynamics.
- Higher packed cell volumes lead to increased coronary artery pressure and resistance.
- Left ventricular end-diastolic and great cardiac vein pressures were not significantly affected by packed cell volume.
Abstract:
To elucidate the role of the haemorheological properties of the perfusate in the coronary circulation, the diastolic pressure-flow relation was studied in nine open chest heart blocked dogs with minimal vasomotor tone when blood with various packed cell volumes (12-67%) was used as perfusate. An electrical analogue model with proximal resistance R1, capacitance C, distal resistance R2, and the zero flow pressure intercept Pint was derived from the observation of the pressure-flow relation to support the data analysis. The diastolic pressure decay was then determined after the perfusion line had been clamped to calculate stop flow coronary artery pressure (Psf). The stop flow coronary artery pressure decreased in relation to packed cell volume (r = 0.45, p less than 0.01), and the value for the lowest packed cell volume (10-29%) was slightly higher than the great cardiac vein pressure (about 3 mmHg). The zero flow pressure intercept of the steady state pressure-flow relation showed a close correlation with the stop flow coronary artery pressure (r = 0.87, p less than 0.001). The value of R1 + R2, which reflects the inverse of the steady state pressure-flow slope, decreased simultaneously with the packed cell volume (r = 0.62, p less than 0.001). The resistance ratio R2/(R1 + R2) by our model prediction decreased in relation to packed cell volume (r = 0.5, p less than 0.001). The values of stop flow coronary artery pressure, zero flow pressure intercept, and R1 + R2 for the highest packed cell volume (50-69%) were 17.8(1.1) mmHg, 25.1(1.3) mmHg, and 0.48(0.05) mmHg.ml-1.min.100 g-1 respectively, whereas those for the lowest packed cell volume (10-29%) were 13.4(0.8) mmHg, 19.7(1.0) mmHg, and 0.24(0.02) mmHg.ml-1.min.100 g-1. The pressure difference between the stop flow coronary artery pressure and the zero flow pressure intercept may be due to the non-linearity in the pressure-flow relation at a low perfusion pressure. The left ventricular end diastolic pressure and great cardiac vein pressure did not change in relation to the packed cell volume of the coronary perfusate. Thus it is concluded that packed cell volume is one factor determining the high zero flow pressure.