Keiichiro Mito

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.

An optical-fiber laser Doppler velocimeter and its application to measurements of coronary blood flow velocities

In this paper we describe a laser Doppler velocimeter (LDV) with an optical fiber that measures blood flow velocities accurately in a small sample volume. The principle, optical arrangement, spatial and the temporal resolutions and accuracy for blood flow measurements are delineated, followed by a report of the results of measurements of coronary artery and vein blood flow velocities in dogs. Finally, we touch upon some recent progress made in the LDV with an optical fiber pickup.

Evaluation of Coronary Blood Flow by Fiber-Optic Laser Doppler Velocimeter

Our laser Doppler velocimeter (LDV) with an optical fiber is a powerful tool for the measurement of both coronary artery and vein flow velocities because of its excellent accessibility to the coronary vessels of a moving heart. In this paper, we briefly describe the optical arrangement of the LDV and then introduce some results of measurements of the blood velocity patterns of epicardial large coronary vessels, and epicardial small arteries and veins obtained by two different routes of access of fiber probe. We also touch upon the dual-core-fiber system which is probably promising as a Doppler catheter for clinical use

A laser Doppler catheter for monitoring both phasic and mean coronary vein flow.

SummaryA new catheter-type laser Doppler velocimeter has been developed to monitor coronary vein flow. A thin graded-index multimode optical fiber (outer diameter of 125 µm) is set inside a 5-F catheter, and eight elastic silicon rubber spikes are arranged radially toward the vessel wall to fix the catheter tip in or near the axial region of the coronary vein. He-Ne laser light (wave length =632.8nm) is introduced into the blood through the optical fiber, and reflected light is collected by the same fiber. The Doppler signal is detected by a spectrum analyzer. To avoid any effect by the spikes on flow, the fiber is extended from the catheter tip by 3 mm at the time of measurement. Straight and curved tubing was used to examine the accuracy of flow measurement. The flow velocities recorded by the catheter, which were measured by an electromagnetic flowmeter, exhibited excellent linearity (r= straight: 0.982, curved: 0.996). The blood flow velocity in the great cardiac vein was measured by this method in five dogs. The predominantly systolic waveform, which is a characteristic of the coronary vein flow, was observed in all of the dogs. The great cardiac vein velocity increased around the beginning of the ventricular ejection and decreased gradually after the peak formation at mid- or end-diastole. In addition to this main peak, small flow components were frequently observed during isovolumic contraction and the atrial contraction phase, although these flow components varied in individual dogs. Following left anterior descending artery occlusion, the great cardiac vein flow velocity decreased significantly. Following reopening of the left anterior descending artery, the great cardiac vein flow velocity increased, showing a reactive hyperemic response, and then it returned to the control level. In conclusion, our catheter-type laser Doppler velocimeter holds promise for continuous monitoring of both mean and pulsatile coronary vein flow velocities in man.

Dual-fiber laser doppler velocimeter and its application to the measurements of coronary blood velocity

To obtain a smaller sample volume and a suitable sample position for the measurement of blood velocity, we fabricated a laser Doppler velocimeter (LDV) with a dual-fiber pickup. The two fibers (clad: 62.5 micron and core: 50 micron) were placed side by side. An He-Ne laser was introduced into the blood through one fiber and the backscattered light was collected by the other fiber. The Doppler signal was analyzed by a spectrum analyzer. The spectrum of the Doppler shift frequency showed a sharp peaked pattern for both forward and reverse flows and exhibited an excellent correlation with the known blood velocity. The blood velocity in the poststenotic portion of canine coronary artery was successfully measured by the dual-fiber LDV. These results indicate that the dual-fiber LDV is useful for measuring blood velocity accurately with a small sample volume even in disturbed flow fields.

Laser Doppler Blood Flow Velocimeter With An Optical Fiber And Its Application To Detailed Measurements Of The Coronary Blood Flow Velocities

In this study we present a new laser Doppler velocimeter (LDV) with an optical fiber to measure blood flow velocities accurately. After fundamental experiments to evaluate the accuracy and performances of this LDV in the blood velocimetry, blood flow velocity profiles in coronary arteries were evaluated in mongrel dogs. It was shown that this LDV is a feasible and useful to measure the dynamic blood flow velocity in coronary arteries. Finally, our LDV was remodeled to a catheter type for clinical application.

Evaluation of Blood Flow Velocity Waveforms in Intramyocardial Artery and Vein by Laser Doppler Velocimeter with an Optical Fiber

It is well established that the part of the left ventricle at greatest risk to ischemia is the subendocardium. Both in myocardial infarction in humans and experimental myocardial infarction in dogs, the subendocardial muscle shows the most extensive necrosis and the subepicardium is spared. Thus, it is important to evaluate phasic blood flow in deeper intramyocardial layers. Measurements, however, have been restricted in the region of epimyocardium because of the methodological limitations [1–3].

Evaluation of the Velocity Waveform in Intramyocardial Small Vessels

We measured the blood flow velocities in intramyocardial septal arteries and intramyocardial small veins by our laser Doppler velocimeter (LDV) with an optical fiber. The blood flow velocity pattern in the septal artery was almost exclusively diastolic and always accompanied by a reverse flow during isovolumic contraction. The blood flow velocity pattern of the intramyocardial vein increased rapidly during the isovolumic contraction phase and decelerated after the beginning of diastole. Following nitroglycerin administration, the forward flow in the intramyocardial small vein shows a reciprocal relation with the reverse flow in the intramyocardial artery, indicating that the phasic blood flow velocity patterns in the intramyocardial artery and vein are subject to the effect of myocardial contraction and relaxation on the intramyocardial capacitance vessels.

A Study of Coronary Circulation by Laser Doppler Velocimetry

Our laser Doppler velocimeter (LDV) with an optical fiber is a powerful tool for the measurement of both coronary artery and vein flow velocities because of its excellent accessibility to coronary vessels of the beating heart. We designed four different accesses of a fiber probe to measure blood velocities, depending upon the objectives of the measurements, i. e., epicardial large coronary vessels, the epicardial small artery and vein, the intramyocardial artery and vein, and a laser catheter. The blood flow velocities showed a diastolic-predominant pattern in the coronary artery and a systolic-predominant pattern in the coronary vein. The phase opposition between arterial and venous flows was more remarkable in intramyocardial vessels, i. e., the systolic reverse flow in the artery showed a reciprocal relation to the systolic forward flow in the vein. In veins, suction of blood from superficial veins to a deeper portion may occur during diastole. The laser Doppler catheter was found to be useful for monitoring coronary vein flows in the coronary sinus and the great cardiac vein. We found that the four different routes of access of optical fiber probe are useful for the evaluation of coronary flows.

Evaluation of Two Fiber Laser Doppler Velocimeter

Laser Doppler velocimetry has been considered to be a promising new technique capable of measuring blood flow velocity accurately in a small sample volume [1,2]. Application of the LDV in medical and biological fields, however, had been restricted to blood velocity measurements in superficial fine vessels with a thin wall [3,4,5,6], since blood and vessel walls have relatively low transparency for laser light. To overcome this restriction, Tanaka and Benedek [7] introduced laser light into the blood stream through an optical fiber catheter and measured the average blood flow in the rabbit femoral vein by taking an autocorrelation of scattering light. However, pulsatile blood velocity could not be measured in real time by this method nor could reverse flow be differentiated from forward flow. The optical fiber was too thick (500 μm o.d.) for practical use. In order to apply LDV to real-time observation of phasic arterial and venous blood flow velocity, one should be able to measure the blood flow velocity with a high temporal resolution and also to discriminate the reverse from the forward component. To apply the LDV to real-time observation of phasic arterial and venous blood flow velocities, we developed a high-resolution LDV using a thin optical fiber [8,9,10,11]. Kilpatrick also developed an LDV with an optical fiber and demonstrated its utility for blood velocity measurements in the coronary vein [12]. We particularly intended to apply our method to an analysis of the blood flow velocity in the coronary vascular system. Our LDV with an optical fiber has the following advantages: 1) high spatial resolution — (100 μm); 2) high temporal resolution (−8ms), and 3) excellent accessibility with a flexible thin fiber sensor [8,9,10,13]. Blood velocity measurements can be performed satisfactorily in non-disturbed flows, accurate flow detection is difficult with a single fiber system, since the Doppler signal contains the flow information from the fiber tip (zero velocity) to the actual velocity. To widen the applicability of an optical fiber type LDV, e.g. blood velocity measurements in a disturbed flow field,we tested an LDV with two fibers [14,15], which extends the sensing field away from the fiber tip [16]. We used the system to measure blood velocities at poststenotic portions of the canine coronary artery.