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.

Techniques for arteriography and hydraulic analysis of coronary stenoses in unsedated dogs

1978 ◽  
Vol 235 (3) ◽  
pp. H350-H356 ◽  
Author(s):  
K. L. Gould ◽  
D. Lee ◽  
K. Lovgren
Keyword(s):  
Flow Velocity ◽  
Coronary Flow ◽  
Flow Characteristics ◽  
Doppler Velocity ◽  
Coronary Flow Velocity ◽  
X Ray ◽  
Pressure Losses ◽  
Coronary Stenoses ◽  
Velocity Pressure ◽  
Perivascular Cuff

This report describes techniques for obtaining pressure flow characteristics and arteriograms of controlled coronary stenoses in unsedated, trained dogs. Coronary flow velocity was recorded by calibrated Doppler velocity transducers linear to three times maximum coronary flow velocity. Pressure losses across stenoses were measured by a differential pressure transducer through small catheters implanted in the distal and proximal left circumflex coronary artery or ascending aorta, a system that was linear within +/-5% to 30 Hz. Coronary stenoses were produced by saline-filled, perivascular cuff constrictors inflated to constant pressure by a pressure regulator. Catheters were implanted in the pulmonary artery for injection of intravenous drugs or diffusible radionuclides and in the left atrium for injection of radionuclide microspheres. Contrast medium was injected through the proximal coronary catheter, and high-resolution arteriograms were obtained by single-spot filming on ultra detail X-ray film and cassettes at end diastole by triggering X-ray exposures from the electrocardiogram. In 13 dogs studied consecutively, the surgical mortality was 15.4%. All implanted instruments functioned for an average of 8 wk per dog.

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.

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 Detailed Precision of Computed Tomography Angiography Compared to Invasive Angiography in Different Coronary Vessels: Overestimate, Underestimate, or Concordance?

2018 ◽  
Vol 39 (1) ◽  
pp. 7-14
Author(s):  
TM Haykal ◽  
Elen Elen ◽  
Celly A. Atmadikoesoemah ◽  
Abhirama N Putra ◽  
Andrew Parlautan ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Quantitative Analysis ◽  
Coronary Angiography ◽  
Computed Tomography Angiography ◽  
Invasive Coronary Angiography ◽  
Coronary Vessels ◽  
Obstructive Lesion ◽  
Stenosis Quantification ◽  
Classification Quantitative ◽  
Sensitivity Specificity

Background: Quantitative analysis of stenosis lesions by Computed Tomography angiography (CTA) show good correlation with Invasive Coronary Angiography (ICA) examination. However, detailed precision whether CTA overestimate or underestimate have not been explored thoroughly. Objectives: This research is performed to analyze the precision of CTA compared to ICA. Materials & Methods: There are 195 patients examined by both CTA and ICA from October 2014 until December 2015 in our hospital. CTA was analyzed by a team of cardiovascular imaging cardiologists. Quantitative grading of stenosis was determined visually using 2014 Society of Cardiovascular Computed Tomography (SCCT) guidelines classification. Quantitative measurement of stenosis during ICA was classified with the same criteria so that it can be comparable. The final comparison of both tests was clas­sified as concordance, overestimate and underestimate. Results: Lesion of stenosis was found in 573 coronary vessels. Coronary vessels are significantly associated with detailed precision of quantitative analysis comparison in CTA and ICA. LM coronary stenosis quantification from CTA is predominantly overestimate (concordance in 6% vessels and overestimate in 75.9% vessels), while stenosis analysis by CTA in other major coronary vessels is spread without conspicuous domination (p<0.001). Sensitivity, specificity, PPV, and NPV of CTA to detect obstructive lesion (stenosis ≥ 50%) found by ICA is 81.4%, 80.4%, 73.9%, and 86.3%, respectively (780 vessels). Conclusions: Degree of stenosis in LM is predominantly overestimate by CTA. The precision of stenosis grading in CTA in different coronary vessels is not the same.   Abstrak Latar Belakang: Analisis kuantitatif lesi stenosis pada pembuluh koroner menggunakan modalitas Computed Tomography Angiography (CTA) memiliki korelasi yang baik dengan pemeriksaan Invasive Coronary Angiography (ICA). Namun, presisi CTA terhadap ICA masih belum ter­eksplorasi dengan baik. Terutama dari sisi apakah CTA menunjukkan presisi yang overestimate atau underestimate. Tujuan: Penelitian ini dilakukan untuk menganalisis presisi CTA terhadap ICA dalam mendeteksi lesi stenosis pada pembuluh koroner. Metode Penelitian: Terdapat 195 pasien yang diperiksa menggunakan CTA dan ICA sejak Oktober 2014 hingga Desember 2015 di RS Jan­tung dan Pembuluh Darah Harapan Kita, Jakarta. Analisis kuantitatif CTA dilakukan oleh tim kardiolog pencitraan kardiovaskular. Klasifikasi derajat stenosis ditentukan secara visual menggunakan pedoman dari Society of Cardiovascular Computed Tomography (SCCT) 2014. Analisis kuantitatif lesi stenosis dari pemeriksaan ICA diklasifikasikan menggunakan pedoman yang sama sehingga keduanya dapat diperbandingkan. Data hasil perbandingan kedua modalitas diklasifikasikan sebagai concordance, overestimate dan underestimate. Hasil Penelitian: Lesi stenosis ditemukan pada 573 pembuluh koroner. Pembuluh koroner yang berbeda secara signifikan berhubungan dengan perbandingan klasifikasi analisis semi-kuantitatif CTA dan ICA. Pembuluh koroner LM terutama menunjukkan lesi dengan kategori overestimate (75.9%). Sementara analisis stenosis pada pembuluh koroner lainnya tidak menunjukkan perbedaan yang mencolok (p < 0,001). Sensitivitas, spesifisitas, PPV, dan NPV CTA dalam mendeteksi lesi koroner obstruktif (stenosis ≥50%) terhadap ICA adalah sebesar 81.4%, 80.4%, 73.9%, dan 86.3% (780 pembuluh kroner). Kesimpulan: Analisis stenosis semi-kuantitatif pada LM terutama adalah overestimate berdasarkan pemeriksaan CTA. Presisi analisis perband­ingan derajat stenosis CT angiografi pada setiap pembuluh koroner tidak sama.

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.

Abstract P531: Cerebral Blood Flow Analysis Using Flow Wire Measurements and CFD Analysis

Stroke ◽  
2021 ◽  
Vol 52 (Suppl_1) ◽  
Author(s):  
Aichi Chien ◽  
Huy Dinh ◽  
Viktor Szeder ◽  
Fernando Vinuela
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Flow Velocity ◽  
Cfd Simulation ◽  
Cfd Analysis ◽  
Flow Data ◽  
Velocity Data ◽  
Mean Flow ◽  
Good Agreement ◽  
Cerebral Vascular

Introduction: Clinical reports show that cerebral blood flow conditions are indicative of cerebral vascular disease. While methods for characterizing cerebral vascular flow have been extensively reported in the past, comparative analyses between direct flow measurements (DM) and computational flow dynamic (CFD) analysis remain limited. We hypothesize that flow data can be reliably measured both directly and through CFD in normal vessels. Methods: A left heart replicator was used as a realistic cardiac pump which maintained systolic pressure at 120 mmHg and diastolic pressure at 80 mmHg. A stenotic model with 50% stenosis for the ICA was connected to the replicator. A ComboWire was used for DM and recorded flow pressure and velocity. CFD was used to study flow. Results: In areas at the proximal end of the stenosis, the pressure and flow velocity derived from DM and CFD were in good agreement. At the end of systole and diastole, DM pressure were 145.42 mmHg and 73.53 mmHg, respectively. CFD simulation for the same system obtained the pressure at the end of systole and diastole of 147.16 mmHg and 74.64 mmHg, respectively. The velocity data collected from DM was at 15.40 cm/s and 7.74 cm/s for systolic flow and mean flow velocity. CFD measured flow was 17.85 cm/s and 11.37 cm/s, respectively. In areas at the distal end of the stenosis, pressure data showed good agreement between DM and CFD analysis. The DM were 138 and 70.81 mmHg at the end of systole and diastole, respectively; CFD simulation yielded 145.95 and 74.51 mmHg, respectively. Variations in the velocity data were observed at this location (Fig, pink arrows). Conclusion: DM of pressure showed good agreement with CFD simulation in all areas of the vessel. DM of velocity using the flow wire were highly affected by location of the measurement. CFD analysis can provide more consistent flow data for flow information collection along the vasculature.

scholarly journals Simplified Calibration Method for Constant-Temperature Hot-Wire Anemometry

2020 ◽  
Vol 10 (24) ◽  
pp. 9058
Author(s):  
Hidemi Takahashi ◽  
Mitsuru Kurita ◽  
Hidetoshi Iijima ◽  
Seigo Koga
Keyword(s):  
Boundary Layer ◽  
Flow Velocity ◽  
Constant Temperature ◽  
Calibration Method ◽  
Large Temperature ◽  
Velocity Data ◽  
Hot Wire ◽  
Temperature Variations ◽  
Wire Temperature ◽  
Hot Wire Anemometry

This study proposes a unique approach to convert a voltage signal obtained from a hot-wire anemometry to flow velocity data by making a slight modification to existing temperature-correction methods. The approach was a simplified calibration method for the constant-temperature mode of hot-wire anemometry without knowing exact wire temperature. The necessary data are the freestream temperature and a set of known velocity data which gives reference velocities in addition to the hot-wire signal. The proposed method was applied to various boundary layer velocity profiles with large temperature variations while the wire temperature was unknown. The target flow velocity was ranged between 20 and 80 m/s. By using a best-fit approach between the velocities in the boundary layer obtained by hot-wire anemometry and by the pitot-tube measurement, which provides reference data, the unknown wire temperature was sought. Results showed that the proposed simplified calibration approach was applicable to a velocity range between 20 and 80 m/s and with temperature variations up to 15 °C with an uncertainty level of 2.6% at most for the current datasets.

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