To analyze the effect of coronary stenosis on the phasic pattern of blood flow velocity into the myocardium, we measured septal artery blood velocities under control conditions, i.e., no stenosis (N), with moderate (S1) and severe (S2) proximal coronary arterial stenosis, and during complete occlusion. In eight anesthetized open-chest dogs, the blood velocity measurements were performed using our 20-MHz multichannel pulsed Doppler method before and after intracoronary adenosine administration. Under N, the coronary perfusion pressure was set to approximately 100 mmHg, with S1 the poststenotic pressure was approximately 60 mmHg, and with S2 it was decreased to 35 mmHg. Septal arterial blood velocity area, which is the time-integrated envelope of the velocity, was divided into three components; systolic retrograde velocity area, systolic anterograde velocity area, and diastolic anterograde velocity area. There were no significant changes from N to S1 in any of the three velocity areas, which is a measure of the flow. Total inflow decreased from N to S2 by 52% (P less than 0.05). Diastolic anterograde flow decreased from N to S2 by 32% (P less than 0.05). Systolic retrograde flow increased from N to S2 by 75% (P less than 0.05). Systolic anterograde flow was almost unchanged by increasing stenosis. After complete occlusion, the septal artery exhibited a to-and-fro flow pattern. Adenosine-induced vasodilation reduced poststenotic pressure (P less than 0.05) and enhanced systolic retrograde flow without a significant increase in diastolic anterograde flow. Systolic retrograde flow increased at S1 by 49% (P less than 0.05) and at S2 by 27% (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)