Blood Velocity Profiles Along Poststenotic Coronary Artery and Stenotic Intramyocardial Flow
To evaluate the effect of coronary stenosis on coronary flow, we evaluated: (1) the blood velocity profiles across the vessel at portions distal to stenosis, (2) the velocity waveform in the septal artery during left main coronary artery stenosis with or without vasodilators, and (3) transmural flow distribution with low perfusion pressure as in stenosis before and after intracoronary nitroglycerin. The experiments were performed in 29 dogs using our 80-channel 20 MHz ultrasound velocimeter. The poststenotic velocity configuration was characterized by a narrow region of high velocity with diastolic reverse flows near the wall which may dissipate energy. Septal artery blood flow velocity which reflected myocardial inflow showed a diastolic-predominant waveform always accompanied by a systolic retrograde blood velocity component. Coronary artery stenosis enhanced the systolic retrograde flow with a decrease in diastolic flow, reducing myocardial inflow. The systolic retrograde flow was augmented further by coronary vasodilation (intracoronary adenosine or nitroglycerin) and did not improve myocardial inflow (or decreased it). Intracoronary nitroglycerin increased epimyocardial flow, but did not increase endomyocardial flow. In conclusion, an augmented retrograde flow which is increased by vasodilators plays an important role in disturbing myocardial inflow during coronary artery stenosis. This could be called a “coronary slosh phenomenon”. Thus, increased systolic retrograde flow and the decreased diastolic flow are closely related in reducing myocardial flow, especially subendocardial flow.
KeywordsLeft Anterior Descend Coronary Artery Stenosis Blood Velocity Left Main Coronary Artery Velocity Waveform
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