Abstract
To elucidate the role of hemorheological properties of the perfusate in coronary circulation, the diastolic coronary pressure-flow relationships (PFR) were analysed when blood with various hematocrits (Ht; 10-68%) or fluorocarbon emulsion (Fc) was used as perfusate. The left anterior descending and circumflex coronary arteries in open-chest heart-blocked dogs were cannulated with a Y-shaped cannula the other end of which was connected to a pressure controllable reservoir. The coronary vascular bed was maximally dilated with adenosine. Initially, the coronary arteries were perfused with constant pressure from the reservoir which contains blood with certain Ht or Fc. A long diastole was induced by pacing-off and coronary perfusion pressure was decreased rapidly to a preset target pressure. This procedure was repeated changing target pressure at 5 different levels (0-70mmHg). An electrical analog model with proximal resistance R1, capacitance C, distal resistance R2 and back pressure Pb was derived from the observation of the PFR. Estimation of the parameter values was performed so as to fit all pressure-flow data of 5 pairs of experiments by a non-linear optimization method. When the Ht was reduced in 7 dogs, back pressure decreased significantly (r=0.50, p<0.001). The total resistance R1 + R2 and the resistance ratio R2/(R1 + R2) were correlated significantly with Ht (r=0.84 and 0.65). When Fc was used instead of blood in 7 dogs, back pressure and total resistance decreased whereas change in resistance value was not statistically significant. These results demonstrate a significant contribution of hemorheological characteristics of the coronary perfusate to the diastolic coronary artery pressure-flow relationship. (J. Jpn. Soc. Biorheol., 2(1), 41~50, 1988).
