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1.
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.  相似文献   

2.
Chronic coronary artery stenosis results in patchy necrosis in the dependent myocardium and impairs global and regional left ventricular (LV) function in rats in vivo. The aim of the present study was to compare regional myocardial blood flow (RMBF) and function (F) in poststenotic myocardium by using magnetic resonance imaging (MRI) and to compare MRI blood flow changes to histological alterations to assess whether RMBF in the viable poststenotic tissue remains normal. MRI was performed in 11 anesthetized Wistar rats with 2-wk stenosis of the left coronary artery. Postmortem, the extent of fibrotic tissue was quantified. Poststenotic RMBF was significantly reduced to 2.21 +/- 0.30 ml.g(-1).min(-1) compared with RMBF in the remote myocardium (4.05 +/- 0.50 ml.g(-1).min(-1)). A significant relationship between the poststenotic RMBF (%remote area) and the poststenotic F (%remote myocardium) was calculated (r = 0.61, P < 0.05). Assuming perfusion in scar tissue to be 32 +/- 5% of perfusion of remote myocardium, as measured in five additional rats, and that in remote myocardium to be 114 +/- 25% of that in normal myocardium, as assessed in five sham rats, the calculated perfusion in partially fibrotic tissue samples (35.7 +/- 5.2% of analyzed area) was 2.88 +/- 0.18 ml.g(-1).min(-1), whereas measured MRI perfusion was only 1.86 +/- 0.24 ml.g(-1).min(-1) (P < 0.05). These results indicate that resting perfusion in viable poststenotic myocardium is moderately reduced. Alterations in global and regional LV function are therefore secondary to both patchy fibrosis and reduced resting perfusion.  相似文献   

3.
Twenty fetal lambs were studied in utero using continuous wave Doppler ultrasound to analyse the fetal umbilical artery flow velocity waveforms. Satisfactory waveforms were obtained. Prepregnancy surgical removal of uterine caruncles was used to produce intrauterine fetal growth retardation in 14 of these ovine pregnancies of whom 8 delivered a small for gestational age fetus. In only one fetus was the umbilical artery flow velocity waveform abnormal with a high systolic diastolic ratio. We conclude that the growth restriction occurring in the ovine fetus following a reduction of placental implantation sites is not related to a restriction in the fetoplacental circulation and this is different from the most frequently observed human fetal growth retardation.  相似文献   

4.
In placental insufficiency and pre-eclampsia the relative production rates of prostacyclin and thromboxane by the placenta and umbilical vessels are altered and the Doppler umbilical flow velocity waveform shows a high resistance pattern. To investigate the control of umbilical placental blood flow by those eicosanoids either prostacyclin (10 micrograms/min), or the thromboxane analogue U46619 (10 ng/min) was infused into the distal aorta of 12 chronically catheterized fetal lambs at day 125. Thromboxane produced a rise in mean arterial pressure and a rise in the systolic diastolic ratio of the umbilical artery flow waveform (2.6 to 3.1; P less than 0.05). Umbilical blood flow did not change and there was no evidence of altered flow to other organs. Prostacyclin caused a fall in fetal mean arterial pressure and a decrease in the umbilical artery systolic diastolic ratio (2.9 to 2.4; P less than 0.05). Prostacyclin produced a three-fold increase in lung perfusion (and the onset of fetal breathing movements) and this was associated with a 90% reduction in muscle blood flow (hindlimb muscle flow reduced from 12.5 to 1.1 ml.min-1 100g-1; P less than 0.01). We conclude that the local release of thromboxane in the fetal placental vascular bed could account for the rise in systolic diastolic ratio seen in umbilical placental insufficiency.  相似文献   

5.

Background

Myocardial contrast echocardiography and coronary flow velocity pattern with a rapid diastolic deceleration time after percutaneous coronary intervention has been reported to be useful in assessing microvascular damage in patients with acute myocardial infarction.

Aim

To evaluate myocardial contrast echocardiography with harmonic power Doppler imaging, coronary flow velocity reserve and coronary artery flow pattern in predicting functional recovery by using transthoracic echocardiography.

Methods

Thirty patients with anterior acute myocardial infarction underwent myocardial contrast echocardiography at rest and during hyperemia and were quantitatively analyzed by the peak color pixel intensity ratio of the risk area to the control area (PIR). Coronary flow pattern was measured using transthoracic echocardiography in the distal portion of left anterior descending artery within 24 hours after recanalization and we assessed deceleration time of diastolic flow velocity. Coronary flow velocity reserve was calculated two weeks after acute myocardial infarction. Left ventricular end-diastolic volumes and ejection fraction by angiography were computed.

Results

Pts were divided into 2 groups according to the deceleration time of coronary artery flow pattern (Group A; 20 pts with deceleration time ≧ 600 msec, Group B; 10 pts with deceleration time < 600 msec). In acute phase, there were no significant differences in left ventricular end-diastolic volume and ejection fraction (Left ventricular end-diastolic volume 112 ± 33 vs. 146 ± 38 ml, ejection fraction 50 ± 7 vs. 45 ± 9 %; group A vs. B). However, left ventricular end-diastolic volume in Group B was significantly larger than that in Group A (192 ± 39 vs. 114 ± 30 ml, p < 0.01), and ejection fraction in Group B was significantly lower than that in Group A (39 ± 9 vs. 52 ± 7%, p < 0.01) at 6 months. PIR and coronary flow velocity reserve of Group A were higher than Group B (PIR, at rest: 0.668 ± 0.178 vs. 0.248 ± 0.015, p < 0.0001: during hyperemia 0.725 ± 0.194 vs. 0.295 ± 0.107, p < 0.0001; coronary flow velocity reserve, 2.60 ± 0.80 vs. 1.31 ± 0.29, p = 0.0002, respectively).

Conclusion

The preserved microvasculature detecting by myocardial contrast echocardiography and coronary flow velocity reserve is related to functional recovery after acute myocardial infarction.  相似文献   

6.
Numerical simulations of pulsatile blood flow in straight tube stenosis models were performed to investigate the poststenotic flow phenomena. In this study, three axisymmetrical and three asymmetrical stenosis models with area reduction of 25%, 50% and 75% were constructed. A measured human common carotid artery blood flow waveform was used as the upstream flow condition which has a mean Reynold's number of 300. All calculations were performed with high spatial and temporal resolutions. Flow features such as velocity profiles, flow separation zone (FSZ), and wall shear stress (WSS) distributions in the poststenotic region for all models are presented. The results have demonstrated that the formation and development of FSZs in the poststenotic region are very complex, especially in the flow deceleration phase. In axisymmetric stenoses the poststenotic flow is more sensitive to changes in the degree of stenosis than in asymmetric models. For severe stenoses, the stenosis influence length is shorter in asymmetrical models than in axisymmetrical cases. WSS oscillations (between positive and negative values) have been observed at various downstream locations in some models. The amplitude of the oscillation depends strongly on the axial location and the degree of stenosis.  相似文献   

7.
A validation study and early results for non-invasive, in vivo measurement of coronary artery blood flow using phase contrast magnetic resonance imaging (PC-MRI) at 3.0T is presented. Accuracy of coronary artery blood flow measurements by phase contrast MRI is limited by heart and respiratory motion as well as the small size of the coronary arteries. In this study, a navigator echo gated, cine phase velocity mapping technique is described to obtain time-resolved velocity and flow waveforms of small diameter vessels at 3.0T. Phantom experiments using steady, laminar flow are presented to validate the technique and show flow rates measured by 3.0T phase contrast MRI to be accurate within 15% of true flow rates. Subsequently, in vivo scans on healthy volunteers yield velocity measurements for blood flow in the right, left anterior descending, and left circumflex arteries. Measurements of average, cross-sectional velocity were obtainable in 224/243 (92%) of the cardiac phases. Time-averaged, cross-sectional velocity of the blood flow was 6.8+/-4.3cm/s in the LAD, 8.0+/-3.8cm/s in the LCX, and 6.0+/-1.6cm/s in the RCA.  相似文献   

8.
Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow reserve (CFR) in humans. Reduced CFR is accompanied by marked intramyocardial and pericoronary fibrosis and is used as an indication of the severity of dysfunction. This study explores, step-by-step, the real-time changes measured in the coronary flow velocity, CFR and systolic to diastolic peak velocity (S/D) ratio in the setting of an aortic banding model in mice. By using a Doppler transthoracic imaging technique that yields reproducible and reliable data, the method assesses changes in flow in the septal coronary artery (SCA), for a period of over two weeks in mice, that previously either underwent aortic banding or thoracotomy. During imaging, hyperemia in all mice was induced by isoflurane, an anesthetic that increased coronary flow velocity when compared with resting flow. All images were acquired by a single imager. Two ratios, (1) CFR, the ratio between hyperemic and baseline flow velocities, and (2) systolic (S) to diastolic (D) flow were determined, using a proprietary software and by two independent observers. Importantly, the observed changes in coronary flow preceded LV dysfunction as evidenced by normal LV mass and fractional shortening (FS). The method was benchmarked against the current gold standard of coronary assessment, histopathology. The latter technique showed clear pathologic changes in the coronary artery in the form of peri-coronary fibrosis that correlated to the flow changes as assessed by echocardiography. The study underscores the value of using a non-invasive technique to monitor coronary circulation in mouse hearts. The method minimizes redundant use of research animals and demonstrates that advanced ultrasound-based indices, such as CFR and S/D ratios, can serve as viable diagnostic tools in a variety of investigational protocols including drug studies and the study of genetically modified strains.  相似文献   

9.
The velocity of blood in a major epicardial coronary vein accompanying the left anterior descending coronary artery of dogs was measured by means of a 140-micron fiber optic probe connected to a laser Doppler velocimeter. Right atrial pressure, left ventricular intramyocardial and cavity pressures, aortic pressure, as well as peripheral and central coronary venous pressures were compared with the velocity of blood measured in the epicardial coronary vein midway between the sites of the catheters measuring proximal and distal coronary vein pressures. During control conditions, coronary vein velocity was 14-18 cm/s during systole and 1.0-2.1 cm/s during diastole. Right stellate ganglion stimulation, norepinephrine or isoproterenol increased diastolic coronary vein velocity significantly, whereas left stellate ganglion stimulation did not. Average peak systolic velocity was not affected by these interventions. During these positive inotropic interventions, the peak coronary vein velocity usually occurred later in the cardiac cycle than during control conditions. Positive inotropic interventions appeared to decrease coronary vein velocity during systole and increase it during diastole. Left vagosympathetic trunk stimulation decreased diastolic but not systolic coronary vein velocity and usually caused peak coronary vein velocity to occur earlier in the cardiac cycle than during control states. Changes induced by vagosympathetic trunk stimulation usually occurred within one cardiac cycle. It is concluded that coronary vein blood velocity can be influenced by the autonomic nervous system.  相似文献   

10.
A method of retrograde perfusion of the myocardium has been developed in dogs. It consists of a double lumen balloon-tipped catheter inserted transvenously into the coronary sinus, with one lumen connected to a roller pump, the other to a helium counterpulsing pump. Oxygenated heparinized blood is obtained from the femoral artery and pumped continuously into the coronary sinus at a pressure of 50-75 mm Hg. The balloon is inflated during diastole, sealing the coronary sinus and promoting retrograde flow, and is deflated during systole, allowing blood drainage into the right atrium and preventing venous congestion. Thirteen anesthetized open-chest dogs were subjected to 15 minutes of proximal LAD artery occlusion and 30 minutes of diastolic coronary sinus perfusion (DCSP). The area of ischemia was mapped by means of platinum electrodes capable of simultaneously measuring myocardial tissue oxygen tension M(p)O(2)) and electrograms. Reduction of M(p)O(2) with simultaneous elevation of the ST segment on the corresponding electrogram was considered an indication of ischemia. Diastolic coronary sinus perfusion improved myocardial oxygen tension in the ischemic myocardium, reduced ST segment elevation, and tended to restore arterial blood pressure. Histologically, there was no intramyocardial hemorrhage.  相似文献   

11.
The aim of this work was to evaluate the hemodynamic changes in the utero-placental arterial vessels in rabbits (Orictolagus cuniculus) throughout pregnancy as well as those in the umbilical cord, aorta, and caudal vena cava of fetuses to establish their normal reference ranges for systolic peak velocity (SPV), end diastolic velocity (EDV), pulsatility index (PI), and resistance index (RI). The blood flow waveforms were monitored every 4 d in 10 rabbits from Day 10 of pregnancy onward by means of color and pulsed wave Doppler ultrasonography using a 5.5-7.5 MHz microconvex transabdominal probe. The utero-placental blood flow was characterized by steep increases and decrease in the SPV with a slow diastolic wave and relatively high EDV, whereas that of the umbilical artery was discontinuous until Day 22 of pregnancy, when a diastolic waveform was also detectable. From Day 10 to 22 of pregnancy, the fetal aorta blood flow was discontinuous, but thereafter a diastolic peak was measurable. The blood flow of the fetal caudal vena cava was characterized by a systolic peak followed by a small diastolic peak. Throughout the gestation, the SPV and the EDV of maternal and fetal vessels increased (α < 0.05), whereas the PI and the RI decreased (α < 0.05), except for the utero-placental vessels. This work confirms that the rabbit could also be a valid experimental animal model to study, by Doppler ultrasonography, functional hemodynamic changes of the fetuses and placenta vessels in both normal and pathophysiologic conditions.  相似文献   

12.
The influence of left ventricle pressure and volume changes on coronary blood flow was investigated in eight anesthetized dogs. Coronary artery pressure-flow relationships were determined at two levels of left ventricular pressure and volume. The distribution of blood flow within the myocardium was also determined when these relationships varied. Reducing left ventricle pressures and volumes increased heart rate. Rate-pressure product, diastolic coronary pressure, myocardial O2 consumption, total, subendocardial and subepicardial flow decreased. Hematocrit and blood gas data were unchanged. The pressure-flow relationships were shifted leftward (p = 0.001) but the range of autoregulation was not altered. At low left ventricle pressures and volumes, the lower coronary artery pressure limit was shifted leftward (from 75 to 45 mm Hg (1 mm Hg = 133.3 Pa)), while total, subendocardial, and subepicardial blood flow did not change compared with the control. Below the lower coronary artery pressure limit, subendocardial but not subepicardial flow decreased, resulting in maldistribution of flow across the left ventricular wall. When coronary pressure was reset between control and the lower coronary artery pressure limit, subendocardial flow was restored. These results show that the lower coronary artery pressure limit can be shifted leftward while the distribution of blood flow across the left ventricular wall is preserved.  相似文献   

13.
14.
In animal studies, sympathetically mediated coronary vasoconstriction has been demonstrated during exercise. Human studies examining coronary artery dynamics during exercise are technically difficult to perform. Recently, noninvasive transthoracic Duplex ultrasound studies demonstrated that 1) patients with left internal mammary artery (LIMA) grafts to the left anterior descending artery can be imaged and 2) the LIMA blood flow patterns are similar to those seen in normal coronary arteries. Accordingly, subjects with LIMA to the left anterior descending artery were studied during handgrip protocols as blood flow velocity in the LIMA was determined. Beat-by-beat analysis of changes in diastolic coronary blood flow velocity (CBV) was performed in six male clinically stable volunteers (60 +/- 2 yr) during two handgrip protocols. Arterial blood pressure (BP) and heart rate (HR) were also measured, and an index of coronary vascular resistance (CVR) was calculated as diastolic BP/CBV. Fatiguing handgrip performed at [40% of maximal voluntary contraction (MVC)] followed by circulatory arrest did not evoke an increase in CVR (P = not significant). In protocol 2, short bouts of handgrip (15 s) led to increases in CVR (18 +/- 3% at 50% MVC and 20 +/- 8% at 70% MVC). BP was also increased during handgrip. Our results reveal that in conscious humans, coronary vasoconstriction occurs within 15 s of onset of static handgrip at intensities at or greater than 50% MVC. These responses are likely to be due to sympathetic vasoconstriction of the coronary circulation.  相似文献   

15.
目的:研究冠心病患者左室舒张功能假性正常化与肱动脉内皮依赖性舒张功能的关系。方法:将75例行选择性冠状动脉造影的患者按冠状动脉病变程度分为单/双支病变组和三支病变组两组,选取48例健康志愿者作为对照组。检测左室舒张功能指标二尖瓣口血流频谱E峰、A峰、E/A比值,同时观察休息时肱动脉反应性充血后内径变化率。结果:单/双支病变组(第一组)E峰、E/A比值下降,肱动脉反应性充血后内径变化率低于正常对照组(P<0.05);三支病变组(第二组)E峰、E/A值无明显改变,肱动脉反应性充血后内径变化率明显低于对照组(P<0.01)。结论:肱动脉内皮依赖性舒张功能可作为鉴别冠心病左室舒张功能假性正常的指标。  相似文献   

16.
Pulsatile poststenotic flow studies with laser Doppler anemometry   总被引:2,自引:1,他引:1  
The pulsatile flow field distal to axisymmetric constrictions in a straight tube was studied using laser Doppler anemometry. The upstream centerline velocity waveform was sinusoidal at a frequency parameter of 7.5 and mean Reynolds number of 600. Stenosis models of 25, 50 and 75% area reduction were employed and velocity data were derived by ensemble averaging methods. Extensive measurements of the pulsatile velocity profiles are reported, and wall shear rates were computed from the near wall velocity profile gradients. The experiments indicate that a permanent region of poststenotic flow separation does not exist even for the severest constriction, in contrast to results for steady flow. Values of wall shear stress were greatest near the throat of the constriction and were relatively low in the poststenotic region, including the region of most intense flow disturbance. Turbulence was found only for the 75% stenosis model and was created only during a segment of the cycle. Although much emphasis has been placed upon turbulence in the detection of arterial stenoses, particularly as identified by Doppler ultrasound spectral broadening, the present study implies that identification of flow disturbances of an organized nature may be more fundamental in recognizing mild to moderate disease. Additionally, the relationship of these flow field results to the animal aortic coarctation model often employed in atherogenesis studies is discussed.  相似文献   

17.
The left ventricular dysfunction following acute pulmowary hypertension remains unexplained. We wondered if acute pulmonary hypertension could alter the transmural flow distribution within the left ventricular myocardium, independent of coronary flow and perfusion pressure. We used a canine preparation in which the left coronary system was perfused at constant flow and induced a two- to three-fold increase in pulmonary artery pressure by banding the pulmonary artery. Regional myocardial blood flow of the left coronary system was measured using radioactive microspheres, injected into the left coronary system before and after 10-30 min of banding of the pulmonary artery. The left ventricular subendocardial:epicardial ratio fell by 12 and 31% (p less than 0.05) of control value, 10 and 30 min, respectively, after banding of the pulmonary artery, the total flow to the left coronary system being kept constant. Left atrial mean pressure increased from 2.9 +/- 2.4 to 3.6 +/- 1.9 and 6.0 +/- 2.1 (p less than 0.05) following banding. The mechanism of the redistribution of coronary flow may relate to inappropriate vasodilation of the right septal myocardium with consequent relative left ventricular subendocardial hypoperfusion which might aggravate left ventricular ischemia in the presence of hypotension and hypoxia.  相似文献   

18.
Despite having almost identical origins and similar perfusion pressures, the flow-velocity waveforms in the left and right coronary arteries are strikingly different. We hypothesized that pressure differences originating from the distal (microcirculatory) bed would account for the differences in the flow-velocity waveform. We used wave intensity analysis to separate and quantify proximal- and distal-originating pressures to study the differences in velocity waveforms. In 20 subjects with unobstructed coronary arteries, sensor-tipped intra-arterial wires were used to measure simultaneous pressure and Doppler velocity in the proximal left main stem (LMS) and proximal right coronary artery (RCA). Proximal- and distal-originating waves were separated using wave intensity analysis, and differences in waves were examined in relation to structural and anatomic differences between the two arteries. Diastolic flow velocity was lower in the RCA than in the LMS (35.1 +/- 21.4 vs. 56.4 +/- 32.5 cm/s, P < 0.002), and, consequently, the diastolic-to-systolic ratio of peak flow velocity in the RCA was significantly less than in the LMS (1.00 +/- 0.32 vs. 1.79 +/- 0.48, P < 0.001). This was due to a lower distal-originating suction wave (8.2 +/- 6.6 x 10(3) vs. 16.0 +/- 12.2 x 10(3) W.m(-2).s(-1), P < 0.01). The suction wave in the LMS correlated positively with left ventricular pressure (r = 0.6, P < 0.01) and in the RCA with estimated right ventricular systolic pressure (r = 0.7, P = 0.05) but not with the respective diameter in these arteries. In contrast to the LMS, where coronary flow velocity was predominantly diastolic, in the proximal RCA coronary flow velocity was similar in systole and diastole. This difference was due to a smaller distal-originating suction wave in the RCA, which can be explained by differences in elastance and pressure generated between right and left ventricles.  相似文献   

19.
《Biorheology》1996,33(3):185-208
An analytical solution for pulsatile flow of a generalized Maxwell fluid in straight rigid tubes, with and without axial vessel motion, has been used to calculate the effect of blood viscoelasticity on velocity profiles and shear stress in flows representative of those in the large arteries. Measured bulk flow rate Q waveforms were used as starting points in the calculations for the aorta and femoral arteries, from which axial pressure gradient ▿P waves were derived that would reproduce the starting Q waves for viscoelastic flow. The ▿P waves were then used to calculate velocity profiles for both viscoelastic and purely viscous flow. For the coronary artery, published ▿P and axial vessel acceleration waveforms were used in a similar procedure to determine the separate and combined influences of viscoelasticity and vessel motion.Differences in local velocities, comparing viscous flow to viscoelastic flow, were in all cases less than about 2% of the peak local velocity. Differences in peak wall shear stress were less than about 3%.In the coronary artery, wall shear stress differences between viscous and viscoelastic flow were small, regardless of whether axial vessel motion was included. The shape of the wall shear stress waveform and its difference, however, changed dramatically between the stationary and moving vessel cases. The peaks in wall shear stress difference corresponded with large temporal gradients in the combined driving force for the flow.  相似文献   

20.
谢进  胡沛  唐冰  李欣  胡钢 《现代生物医学进展》2017,17(14):2685-2688
目的:分析阿托伐他汀对冠心病患者脂蛋白(a)、血清胆固醇酯转运蛋白(CETP)水平的影响及临床疗效。方法:将112例冠心病患者随机分为对照组与观察组,每组56例。对照组患者采用辛伐他汀治疗,观察组患者采用阿托伐他汀治疗。观察并比较两组患者治疗前后血清LP(a),CETP,超敏C-反应蛋白(hs-CRP)及脑钠肽(BNP)水平,冠状动脉血流储备、舒张期峰流速及收缩期峰流速变化,左心室后壁厚度(LVPWT)、左心室收缩末期内径(LVESD)及左心室舒张末期内径(LVEDD)情况,以及临床疗效。结果:治疗后,观察组LP(a),CETP,hs-CRP及BNP水平均低于对照组,差异有统计学意义(P0.05);观察组冠状动脉血流储备、舒张期峰流速、收缩期峰流速均高于对照组,差异有统计学意义(P0.05);观察组LVPWT、LVESD、LVEDD均低于对照组,差异有统计学意义(P0.05);观察组总有效率高于对照组,差异有统计学意义(P0.05);两组安全性比较,差异无统计学意义(P0.05)。结论:阿托伐他汀对冠心病患者的临床疗效比较明确,可下调LP(a)及血清CETP表达。  相似文献   

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