[Effect of hypoxia on maximal myocardial blood flow in right ventricle]

In order to study the changes of coronary reserve capacity, the effects of hypoxia on hemodynamics and maximal myocardial blood flow in right ventricle were observed. Rats wre divided into 3 groups:normoxic group (control), acute hypoxic group and chronic hypoxic group. Maxmimal myocardial blood flow in the right ventricle was measured with 99 m Tc radiolabelled from RBC during adenosine infusion. The results showed that cardiac output, PaO2 and oxygen delivery were decreased during acute hypoxia, but myocardial blood flow in right ventricle was increased, as compared with the control group. There were no significant change of maximal myocardial blood flow in the right ventricle in acute hypoxic rats. Hematocrit and blood viscosity at different shear rate and RV weight index were augmented, whereas oxygen delivery and myocardial blood flow became normal during chronic hypoxia. Maximal blood flow in RV was significantly decreased whereas arterial wall thickness and collagen in arterial adventitia were increased in chronic hypoxic rats. The above results suggest that the decreased coronary reserve might beresulted from the increasedblood viscosity, arterial wall thickness and collagen in arterial adventitia and right ventricular hypertrophy.