PHASIC CHARACTERISTICS OF ARTERIAL INFLOW AND VENOUS OUTFLOW OF RIGHT VENTRICULAR MYOCARDIUM IN DOGS

To clarify the characteristics and causes of phasic blood flow in coronary circulation of the right ventricle we measured blood velocities in peripheral portions of the right coronary artery and vein in dogs under three conditions: control, transient pulmonary stenosis, and isoproterenol administration. An optical fiber sensor of a laser Doppler velocimeter was fixed onto the vessels (150-500-mu-m OD) with cyanoacrylate. The phasic pattern of distal arterial velocity was compared with the proximal velocity in the right coronary artery measured with an ultrasound pulsed Doppler velocimeter. Systolic-to-total velocity area ratio in the small epicardial artery [0.38 +/- 0.03 (SE)] was found to be smaller than in the large epicardial artery (0.51 +/- 0.02, P < 0.01), indicating a capacitive filling of the epicardial artery during systole. The velocity waveform in small right coronary veins was predominantly systolic; i.e., it increased with a rise of right ventricular pressure and decreased with right ventricular relaxation. Comparison of the waveforms during isoproterenol infusion and pulmonary stenosis indicates that contraction of the ventricle is more important than right ventricular systolic pressure in retarding arterial inflow and accelerating venous outflow.