Phasic coronary blood flow velocity in intramural and epicardial coronary arteries.

Abstract

SUMMARY. Knowledge concerning phasic coronary blood flow is based primarily on measurements obtained from epicardial coronary arteries, which, in part, function as capacitors. If present, epicardial capacitance effects could obscure the dynamic nature of phasic intramyocardial perfusion. To analyze this effect of epicardial capacitance, we simultaneously measured coronary blood flow velocity in an epicardial artery (left anterior descending) and an intramural artery (septal) in openchest, anesthetized dogs. During control conditions, the percentage of total coronary blood flow velocity occurring during diastole per cardiac cycle was significantly greater (P < 0.05) in the septal artery (92%) than in the left anterior descending artery (75%). Furthermore, blood flow velocity during mid-systole in the septal artery was retrograde (-7.2%), whereas blood flow velocity at this time was antegrade in the left anterior descending artery (+3.5%). Blood flow velocity measurements from small epicardial arteries just before they penetrated into the myocardium revealed a phasic pattern similar to that of the septal artery. This suggests that the phasic blood velocity pattern in penetrating coronary arteries, in general, is different than that in large epicardial arteries. During vasodilation following nitroglycerin, dipyridamole, or a 20-second occlusion of the left main coronary artery, the retrograde component of mid-systolic blood velocity persisted in the septal artery, despite large increases (300-400%) in the mid-systolic antegrade component of blood flow velocity in the left anterior descending artery. These qualitative and quantitative differences in phasic blood flow velocity between intramural and large epicardial arteries are best reconciled by postulating the existence of a significant coronary capacitor. (Cite Res 50: 775-781, 1982) IN 1963, Gregg and Fisher speculated about devices that measure phasic coronary blood flow in the following manner:"Since the change in mean vessel tone during a cardiac cycle in the superficial vessels (in which the flow measurements are made) is presumably different from that of the deeper vessels, such a device measures a combination of 'intramural' and 'extramural' flow. It does not, therefore, necessarily indicate correctly the intramural flow at all times."From 1963 to the present, most knowledge concerning phasic coronary flow patterns has been based on measurements obtained from epicardial coronary arteries. Because the epicardial arteries function in part as capacitors (Douglas and Greenfield, 1970), the phasic flow pattern in an epicardial coronary artery may not accurately reflect the phasic pattern of myocardial perfusion. Eckstein and his colleagues, in 1962, theorized that capacitance of epicardial arteries may distort the actual myocardial perfusion in three ways: (1) the magnitude of retrograde flow during systole is concealed because blood expelled from the deep myocardial layers distends the vessels and is not measured; (2) the antegrade systolic flow that is mea...

Scalability and in vivo validation of a multiscale numerical model of the left coronary circulation

“…6) followed a similar trend to that in canine data, reported by Chilian and Marcus (14), in which the early systolic flow transient (called "mid-systole" in Ref. 14) accounted for 3.5 vs. Ϫ7.2% of the total area under the flowvelocity curve in the LAD and septal artery, respectively.…”

“…This compares with 3.2 vs. Ϫ1.4% for our simulated adult group data and 4.3 vs. Ϫ0.7% for the newborn group data (both groups P Ͻ 0.001, LAD vs. septal). By contrast, the flow integral percentage during late systole was not different between these sites in Chilian and Marcus (14) or in our simulated adult group data; however, in the newborn group, LAD and septal arteries accounted for 7.9 and 4.9%, respectively (P Ͻ 0.001).…”

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