Go Tomonaga

Evaluation of phasic blood flow velocity in the great cardiac vein by a laser Doppler method.

SummaryIn the present study, characteristics of the phasic flow pattern in the great cardiac vein and the mechanism of such pattern formation were investigated using a laser Doppler velocimeter with an optic fiber probe. The laser Doppler velocimeter allowed measurements of venous blood velocity under more physiological conditions than were possible with previous methods. Moreover, venous blood flow measurement in the great cardiac vein mirrors the effects of myocardial contraction on the venous flow more directly than does measurement in the coronary sinus. Thus, our method is considered very useful. Results obtained from the present study are as follows: 1) Measurement of the phasic flow in the great cardiac vein was made in 11 anesthetized dogs using our laser Doppler method. The blood velocity curve obtained in the great cardiac vein was always characterized by a prominent systolic flow wave (SFW). The mean value for the maximum velocities under control conditions in 11 cases was 40±13 cm/s. The blood velocity increased with the onset of left ventricular ejection and decreased gradually after the peak formation at mid- or late systole. — 2) Besides the above SFW, one or two small wave components were frequently observed during the atrial contraction period and/or during the isovolumic contraction phase. On the waveform during the atrial contraction period, two cases showed forward flow, while one case showed reverse flow. The small reverse flow waves during the isovolumic contraction phase were found in seven cases. — 3) Pharmacological interventions of dipyridamole and isoproterenol increased the maximum velocity. Compared with dipyridamole, isoproterenol accelerated the rate of rise in the SFW. — 4) No significant coronary venous flow was observed during the diastolic period prolonged by vagal nerve stimulation. However, after coronary vasodilator drugs were administered, there was a transient significant coronary venous flow during the prolonged diastole. This may be the overflow from the coronary capacitance vessels. — 5) During a reactive hyperemic response, the flow velocity of the great cardiac vein increased with the increment of the blood flow volume of the left anterior descending artery. However, its phasic change did not always correspond to that of intramyocardial pressure.

Measurement of point velocity in the canine coronary artery by laser Doppler velocimeter with optical fiber

A laser Doppler velocimeter with an optical fiber was developed to investigate point blood velocity in the arteries and was applied to the measurement of blood velocity in the canine coronary artery Fundamental experiments revealed that the accuracy of this method was satisfactory, since an excellent linear relation was found between the known blood velocity and the Doppler shift frequency (r=0.998). The fiber tip (0.1 mm diam.) was inserted into the proximal portion of the left circumflex coronary artery and was traversed across the vascular lumen to measure the point velocity at each sampling point. Detailed velocity profiles were then reconstructed sequentially in three dimensional coordinates, i.e., velocity, diameter and time. In general the velocity waveform showed a diastolic dominant pattern which is characteristic of coronary arterial flow. One peak in early systole and two peaks in early and in late diastole were commonly observed in the velocity waveform near the center-line of the vessel. The volocity profiles were flat in the axial region and decined abruptly near the vessel wall. These results indicate that the laser Doppler velocimetry with an optical fiber proved to be an accurate and feasible method of evaluating the point velocity of coronary artery flow.