scholarly journals Effect of stenting on the instantaneous diastolic flow velocity: pressure gradient relation in patients with a severe coronary stenosis

2002 ◽  
Vol 39 ◽  
pp. 62
Author(s):  
Koen M. Marques ◽  
H.J. Spruijt ◽  
N. Westerhof ◽  
C.A. Visser ◽  
F.C. Visser
Keyword(s):  
Pressure Gradient ◽  
Flow Velocity ◽  
Coronary Stenosis ◽  
Diastolic Flow ◽  
Velocity Pressure

The diastolic flow velocity-pressure gradient relation and dpv50 to assess the hemodynamic significance of coronary stenoses

2006 ◽  
Vol 291 (6) ◽  
pp. H2630-H2635 ◽  
Author(s):  
Koen M. J. Marques ◽  
Machiel J. van Eenige ◽  
Hugo J. Spruijt ◽  
Nico Westerhof ◽  
Jos Twisk ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Flow Velocity ◽  
Stress Testing ◽  
Coronary Vessels ◽  
Velocity Data ◽  
Severe Stenosis ◽  
Coronary Pressure ◽  
Coronary Stenoses ◽  
Sensitivity Specificity ◽  
Velocity Pressure

To evaluate the hemodynamic impact of coronary stenoses, the fractional (FFR) or coronary flow velocity reserve (CFVR) usually is measured. The combined measurement of instantaneous flow velocity and pressure gradient (v-dp relation) is rarely used in humans. We derived from the v-dp relation a new index, dpv50 (pressure gradient at flow velocity of 50 cm/s), and compared the diagnostic performance of dpv50, CFVR, and FFR. Before coronary angiography was performed, patients underwent noninvasive stress testing. In all coronary vessels with an intermediate or severe stenosis, the flow velocity, aortic, and distal coronary pressure were measured simultaneously with a Doppler and pressure guidewire after induction of hyperemia. After regression analysis of all middiastolic flow velocity and pressure gradient data, the dpv50 was calculated. With the use of the results of noninvasive stress testing, the dpv50 cutoff value was established at 22.4 mmHg. In 77 patients, 124 coronary vessels with a mean 39% (SD 19) diameter stenosis were analyzed. In 43 stenoses, ischemia was detected. We found a sensitivity, specificity, and accuracy of 56%, 86%, and 76% for CFVR; 77%, 99%, and 91% for FFR; and 95%, 95%, and 95% for dpv50. To establish that dpv50 is not dependent on maximal hyperemia, dpv50 was recalculated after omission of the highest quartile of flow velocity data, showing a difference of 3%. We found that dpv50 provided the highest sensitivity and accuracy compared with FFR and CFVR in the assessment of coronary stenoses. In contrast to CFVR and FFR, assessment of dpv50 is not dependent on maximal hyperemia.

Study on the Flow Characteristics of Shengli Oilfield Super Heavy Oil

2017 ◽  
Vol 10 (1) ◽  
pp. 69-78 ◽  
Author(s):  
Wang Shou-long ◽  
Li Ai-fen ◽  
Peng Rui-gang ◽  
Yu Miao ◽  
Fu Shuai-shi
Keyword(s):  
Pressure Drop ◽  
Pressure Gradient ◽  
Heavy Oil ◽  
Flow Characteristics ◽  
Fluid Viscosity ◽  
Linear Flow ◽  
Start Up ◽  
Non Linear ◽  
Core Permeability ◽  
Velocity Pressure

Objective:The rheological properties of oil severely affect the determination of percolation theory, development program, production technology and oil-gathering and transferring process, especially for super heavy oil reservoirs. This paper illustrated the basic seepage morphology of super heavy oil in micro pores based on its rheological characteristics.Methods:The non-linear flow law and start-up pressure gradient of super heavy oil under irreducible water saturation at different temperatures were performed with different permeable sand packs. Meanwhile, the empirical formulas between start-up pressure gradient, the parameters describing the velocity-pressure drop curve and the ratio of gas permeability of a core to fluid viscosity were established.Results:The results demonstrate that temperature and core permeability have significant effect on the non-linear flow characteristics of super heavy oil. The relationship between start-up pressure gradient of oil, the parameters representing the velocity-pressure drop curve and the ratio of core permeability to fluid viscosity could be described as a power function.Conclusion:Above all, the quantitative description of the seepage law of super heavy oil reservoir was proposed in this paper, and finally the empirical diagram for determining the minimum and maximum start-up pressure of heavy oil with different viscosity in different permeable formations was obtained.

scholarly journals Single-Wire Pressure and Flow Velocity Measurement to Quantify Coronary Stenosis Hemodynamics and Effects of Percutaneous Interventions

Circulation ◽  
2004 ◽  
Vol 109 (6) ◽  
pp. 756-762 ◽  
Author(s):  
Maria Siebes ◽  
Bart-Jan Verhoeff ◽  
Martijn Meuwissen ◽  
Robbert J. de Winter ◽  
Jos A.E. Spaan ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Velocity Measurement ◽  
Coronary Stenosis ◽  
Single Wire ◽  
Percutaneous Interventions ◽  
Flow Velocity Measurement

Abstract 14743: Usefulness of Estimated Coronary Flow Velocity Using Quantitative Flow Ratio for Intermediate Coronary Stenosis

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Eiji Ichimoto ◽  
Nao Konagai ◽  
Sawako Horie ◽  
Atsushi Hasegawa ◽  
Hirofumi Miyahara ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Coronary Stenosis ◽  
Coronary Flow ◽  
Flow Ratio ◽  
Operating Characteristics ◽  
Fractional Flow ◽  
Coronary Flow Velocity ◽  
Flow Reserve ◽  
Quantitative Flow Ratio ◽  
Quantitative Flow

Introduction: Quantitative flow ratio (QFR) is a diagnostic modality for functional assessment for intermediate coronary stenosis without the use of pressure wire. QFR is calculated from 3-dimensional quantitative CAG (3D-QCA) using an advanced algorithm that enables fast computation of the pressure drop caused by coronary stenosis. Hypothesis: We assessed the usefulness of QFR and the association with an estimated coronary flow velocity (eCFV) for intermediate coronary stenosis. Methods: A total of 100 lesions in 80 consecutive patients were assessed Fractional Flow Reserve (FFR) for intermediate coronary stenosis between January 2011 and April 2019. Of these, 97 lesions in 77 patients who underwent QFR were included in this study. Patients were classified into two groups (FFR ≤ 0.80 or FFR > 0.80). QFR and eCFV using contrast were measured by Thrombolysis in Myocardial Infarction (TIMI) frame counts. Results: There was no significant differences in target vessels (p = 0.90) and diffuse lesions (p = 0.06) between the two groups (FFR ≤ 0.80 or FFR > 0.80). Mean FFR and QFR values were 0.78 ± 0.12 and 0.77 ± 0.11, respectively. QFR had a good correlation with FFR values (r = 0.86, p < 0.0001). The diagnostic accuracy, sensitivity, and specificity on QFR ≤ 0.80 were 91.8%, 92.7% and 90.5%, respectively. The eCFV of FFR ≤ 0.80 was greater than that of FFR > 0.80 (0.19 ± 0.08 m/s vs. 0.14 ± 0.06 m/s, p<0.001). Figure showed that the eCFV correlated with FFR values (r = -0.29, p < 0.01). Moreover, the eCFV had a high area under the curve (AUC = 0.71, p < 0.01) on Receiver operating characteristics curve (ROC) analysis with FFR ≤ 0.80. Conclusions: QFR was useful for the assessment of functional stenosis severity. As eCFV was faster, FFR was lower for intermediate coronary stenosis. The eCFV had a good correlation with FFR and may become one of the evaluations for ischemia.

Influence of an inclined magnetic field on heat and mass transfer of the peristaltic flow of a couple stress fluid in an inclined channel

2017 ◽  
Vol 14 (1) ◽  
pp. 7-18 ◽  
Author(s):  
Ajaz Ahmad Dar ◽  
K. Elangovan
Keyword(s):  
Magnetic Field ◽  
Mass Transfer ◽  
Pressure Gradient ◽  
Couple Stress ◽  
Pressure Rise ◽  
Peristaltic Flow ◽  
Inclined Magnetic Field ◽  
Content Type ◽  
Inclined Channel ◽  
Velocity Pressure

Purpose This paper aims to intend for investigating the influence of an inclined magnetic field on the peristaltic flow of a couple stress fluid through an inclined channel with heat and mass transfer. Design/methodology/approach Long wavelength and low Reynolds number methodology is actualized for simplifying the highly nonlinear equations. Mathematical expressions of axial velocity, pressure gradient and volume flow rate are obtained. Pressure rise, frictional force and pumping phenomenon are portrayed and symbolized graphically. Exact and numerical solutions have been carried out. The computed results are presented graphically for various embedded parameters. Temperature and concentration profile are also scrutinized and sketched. Findings Results from the current study concluded that the fluid motion can be enhanced by increasing the inclination of both the magnetic field and the channel. Originality/value The elemental characteristics of this analysis is a complete interpretation of the influence of couple stress parameter and inclination of magnetic field on the velocity, pressure gradient, pressure rise and frictional forces.

scholarly journals Doppler ultrasound of umbilical artery in prediction of fetal outcome in pregnancy induced hypertension Sudanese population

2019 ◽  
Vol 8 (1) ◽  
pp. 96
Author(s):  
Rihab A. Yousif ◽  
Awadia G. Suliman ◽  
Raga A. Aburaida ◽  
Ibrahim M. Daoud ◽  
Naglaa E. Mohammed
Keyword(s):  
Flow Velocity ◽  
Umbilical Artery ◽  
Fetal Outcome ◽  
Fetal Mortality ◽  
Pregnancy Induced Hypertension ◽  
Diastolic Flow ◽  
Induced Hypertension ◽  
The Mean ◽  
Doppler Indices ◽  
In Pregnancy

The pregnancy induced hypertension increase the fetal mortality and morbidity and the using of Doppler umbilical artery indices decrease the fetal mortality and morbidity however, there is few complete data about the most frequently altered Doppler US parameters to predict fetal outcome in pregnancy induced hypertension . Methods This ia cohort prospective study done in two hundred and six women of second and third trimester presenting to antenatal clinic in Soba University Hospital at the department of Obstetrics & Gynecology, in the fetus unit and critical pregnancy in the period From June 2008 to April 2013 to assess the Doppler indices of umbilical artery in pregnancy induced hypertension for prediction of prenatal outcome; 105 pregnancy induced hypertension patients and 101 women with uneventful pregnancies as normal control group included in this study . Baseline investigations and color Doppler of umbilical artery were done. Statistical analysis of data were done using SPSS, Receiver Operating Characteristic (ROC) curve analysis was performed and the area under the curve (AUC) used to determine sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of umbilical artery Doppler indices to predict fetal outcome.Results The study determine that there was significant difference in Doppler indices in PIH and control group ( p<0.01, the mean indices of umbilical artery is higher in PIH group compared with normal pregnancy group , the mean different of S/D ratio was 0.40, mean difference of RI was 0.06 and the mean different of PI index was 0.16, high percentage of adverse fetal outcome had been reported in in Pregnancy Induced Hypertension group than in control , which was more in absent and reversed flow velocity in umbilical artery in Pregnancy Induced Hypertension compared with group of Pregnancy Induced Hypertension with present end diastolic flow velocity. Systolic/Diastolic ratio was most accurate in predicting adverse outcome in pregnancy induced hypertension patients, followed by the Pulastility index then the Resistance index (75%, 66% and 57% respectively).ConclusionThis study concluded that pregnancy induced hypertension leads to worsen placental insufficiently, which appears on the higher Doppler indices of umbilical artery to PIH patients when compared with normal pregnancy. A low diastolic flow and higher indices characterized the pregnancies with abnormal outcomes. Doppler of the umbilical artery was useful to predict fetal well being in PIH patients, high percentage of adverse fetal outcome had been reported in absent and reversed end diastolic flow velocity in umbilical artery compared with group of present flow velocity.

scholarly journals Theoretical Study of Heat Transfer on Peristaltic Transport of Non-Newtonian Fluid Flowing in a Channel: Rabinowitsch Fluid Model

2018 ◽  
Vol 3 (4) ◽  
pp. 450-471 ◽  
Author(s):  
U. P. Singh ◽  
Amit Medhavi ◽  
R. S. Gupta ◽  
Siddharth Shankar Bhatt
Keyword(s):  
Heat Transfer ◽  
Pressure Gradient ◽  
Friction Force ◽  
Newtonian Fluid ◽  
Theoretical Study ◽  
Fluid Model ◽  
Pressure Rise ◽  
Peristaltic Flow ◽  
Long Wavelength ◽  
Velocity Pressure

The present investigation is concerned with the problem of heat transfer and peristaltic flow of non-Newtonian fluid using Rabinowitsch fluid model through a channel under long wavelength and low Reynolds number approximation. Expressions for velocity, pressure gradient, pressure rise, friction force and temperature have been obtained. The effect of different parameters on velocity, pressure gradient, pressure rise, streamlines, friction force and temperature have been discussed through graphs.

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