Shinichiro Tadaoka

Analysis of flow characteristics in poststenotic regions of the human coronary artery during bypass graft surgery.

Poststenotic blood flow velocities were evaluated in nine patients with 75% to 99% stenosis of the left anterior descending coronary artery (LAD) during coronary artery bypass graft surgery. We used the 20 MHz 80-channel pulsed Doppler velocimeter developed in our laboratory. An operator placed a specially designed probe on the native LAD with his fingers. Before induction of extracorporeal circulation, LAD blood velocities were measured at several locations distal to the stenosis. The poststenotic flow velocities were rich in systolic flow component with reduced diastolic component. The velocity configuration in the poststenotic portions was characterized by the presence of reverse flow velocities and/or irregularity of the velocity pattern near the vessel wall, indicating the existence of flow separation and recirculation in the regions. The broadening of the velocity spectrum observed at central axial regions suggested the occurrence of flow disturbances. After grafting, the velocity waveform in the LAD beyond a vein bypass graft changed to a diastolic-predominant pattern with a relatively small systolic component. A transient bypass graft occlusion caused a marked reduction in diastolic flow velocity. The systolic-to-diastolic velocity ratio increased from 0.27 +/- 0.07 to 1.50 +/- 0.50 (p less than .01) by the graft occlusion.

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.

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

Measurement accuracy of the flow velocity in pulsed ultrasound Doppler velocimeter

This paper presents a numerical simulation method for evaluating the measurement accuracy of the high-frequency pulsed ultrasound Doppler velocimeter (PUDV). The frequency distribution of the Doppler signal from a sample volume is calculated by dividing the sample volume into small cells and using the statistics of the velocities of the cells. The distribution is used to analyze the accuracy of the poststenotic velocity measurements of a 20-MHz 80-channel PUDV. The target flow field is obtained by solving Navier-Stokes equations numerically. It was shown that the velocities evaluated by the zero-cross and Fourier transform methods agreed well with the given velocities, and that flow separation was successfully detected. It was also shown that the tube diameter should be at least twice as large as the diameter of the sample volume to obtain accurate measurements.

運動負荷後の回復期に収縮期血圧が再上昇する“異常血圧反応”例に関する検討-冠動脈疾患例について

概 要 冠動 脈疾 患 を疑 ってtreadmill(T)負 荷試 験 を行 なった症例 の うち,回 復期 の収縮 期血 圧 が 終了時 よ りも15mmHg以 上上 昇 した35例 につ いて検討 した.24例 は器質 的冠狭 窄(≧75%) を認 め多枝病 変 例が 多か ったが,11例 は正常冠動 脈例 であ った.両 群 と も負 荷中 の血 圧上 昇度 が低 く(19±14mmHg,18±20mmHg),終 了時 におけ るST下 降(-0 .14±0.10mV,-0.18± 0.08mV), P-TFの 著 明 な増 大(4.3±33msec・mV,3.0±1.8msec・mV)を 示 す例 が多 かった. 前 者 は後者 に比 して,T時 間 が短 く,回 復 期の血圧 再上昇 の程度 が著 し く,持 続 時間 の長 い例 が 多か った.回 復 期の血圧 再 上昇 には,重 症 冠動脈 疾患等 にお け る負荷 中の強 い心筋虚 血 に よる 左 心機能 の抑 制 や,最 大運動 負荷 の影響 が考 え られ た.〔日 内会 誌 77:1383~1387, 1988〕

Coronary Blood Flow Velocities in Humans Evaluated During Cardiac Surgery Using a 20 MHz 80+1 Channel Ultrasound Pulsed Doppler Velocimeter

We have developed an 80 + 1 channel high resolution pulsed Doppler velocimeter for measuring in detail the blood flow velocities in relatively small human vessels (1-5 mm in diameter). Real time velocity measurements were performed at 80 sample points using a multigated zero-cross method. The Doppler signal in the desired channel was subjected to real time Fourier analysis. This facilitated analyzing in detail the blood flow velocity profile across vessel, as well as the velocity distribution in a sample volume. The sampling volume was pi X 0.5(2) X 0.2 mm3 and the maximum depth was 1.5 cm. When the incidence angle was selected as 60 degrees, the velocity resolution and maximum velocity were 1.5 and 1.9 m/sec, respectively. Blood flow velocities were measured in the coronary artery and in the aorto-coronary bypass graft in patients during cardiac surgery. The blood flow velocities in the normal coronary artery had a predominantly diastolic pattern which is characteristic of coronary artery flow. Comparing with the systolic forward velocities in the left coronary artery, those of the right coronary artery were more prominent. The velocity wave forms in the graft and in the coronary artery distal to the insertion of the graft had a predominantly diastolic pattern when there was sufficient coronary blood flow through the graft. In contrast, during the occlusion of the graft, the blood velocity wave form in the distal coronary artery became predominantly systolic, indicating insufficient myocardial inflow before the bypass graft. Intravenous dipyridamole administration increased the bypass flow by 50% in a patient who had 100% occlusion before the bypass operation. This indicates that the coronary reserve can still be preserved in some cases of total coronary occlusion. With an intra-aortic balloon pumping (IABP) assist (2:1), the velocity wave form in the graft had predominantly diastolic in both IABP-on and -off beats. However, diastolic augmentation and systolic reduction of the velocity wave form were clearly observed in beats with IABP-on. The velocity wave forms in the anterior descending coronary artery in a patient with aortic regurgitation showed a predominantly systolic pattern with a broad velocity spectrum. After aortic valve replacement, the blood velocity pattern became predominantly diastolic, indicating improvement of the coronary perfusion into the myocardium. In conclusion, our velocimeter proved effective for evaluating coronary blood flow velocities in patients during cardiac surgery.