TCT-478 Thermodilution-Derived Coronary Absolute Flow and Resistance in Patients With and Without Epicardial Stenosis

Myocardial ischemia is the consequence of an unbalance between coronary flow that can be achieved and myocardial metabolic needs. Pathological state of both epicardial and intramyocardial vessels may be responsible for inducing ischemia. However, revascularization decision should be based on the severity of each epicardial lesion that is evaluated. There are different diagnostic tools that may help for the evaluation of each compartment which is based on the measurement of coronary hemodynamics. Pressure-derived indices are recommended by current guidelines for evaluation of epicardial stenosis significance. We assess the complex interaction between hemodynamic parameters in order to understand how different parameters are influenced in the settings of microvascular dysfunction.

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Diagnostic accuracy of Instantaneous Wave-Free Ratio (iFR) for the assessment of myocardial ischaemia: a comparison with non-invasive stress imaging

European Heart Journal ◽

10.1093/ehjci/ehaa946.1369 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

L Stazzoni ◽

L Tessandori ◽

P Spontoni ◽

M Angelillis ◽

C Giannini ◽

...

Keyword(s):

Diagnostic Accuracy ◽

Myocardial Ischaemia ◽

Gold Standard ◽

Coronary Revascularization ◽

Stress Test ◽

Invasive Coronary Angiography ◽

Coronary Syndrome ◽

Non Invasive ◽

Coronary Stenoses ◽

Epicardial Stenosis

Abstract Background Instantaneous Wave-Free Ratio (iFR) allows for the assessment of the haemodynamic effects of epicardial coronary stenoses without the need for hyperaemia; iFR is currently recommended as a means to evaluate myocardial ischaemia. Purpose To assess the diagnostic accuracy of iFR with respect to the identification of coronary epicardial stenoses causing ischemia. Therefore, we combined anatomical (% stenosis at invasive coronary angiography, ICA) and functional (non-invasive imaging stress test, NIST) information to obtain a “gold standard” for the identification of stenoses causing ischaemia. Methods We enrolled 71 patients (52 male, 19 female; age mean 68.4±8.1 years) with chronic coronary syndrome or low-risk acute coronary syndrome without ST segment elevation who had at least a NIST and who had at least one vessel with a 50%-85% stenosis at ICA. iFR was measured in all coronary arteries with stenosis >50% and categorised according to the 0.89 threshold for ischaemia. Results iFR was assessed in 122 vessels. In a per-vessel analysis, in 56.7% ischaemia was present both at iFR and NIST, in 21.3% ischaemia was absent in both, while in 23.0% ischaemia was found at NIST but not confirmed by iFR. The overall accuracy of iFR with respect to NIST was 90.1%. However, when considering as the “gold standard” for coronary disease causing ischaemia the contemporary presence of an epicardial stenosis >70% at ICA and a positive NIST, the diagnostic accuracy of iFR greatly improved. The sensibility, specificity, PPV, NPV and accuracy were 96.5%, 75.0%, 73.3%, 96.7% and 84.4%, respectively. In case of discordance between NIST and iFR, revascularization was based on iFR. At a mean follow-up of 23±18 months, the composite endpoint of MACE (major adverse cardiac events, defined as the composite of all-cause death, nonfatal MI and unplanned coronary revascularization) occurred in 16.4%, while death/MI occurred in 11.9%. Stratification according to the per-patient concordance between iFR and NIST showed no significant differences in rates of MACE (p=0.50) and death/MI (p=0.20). Stratification based on iFR showed a higher death/MI rate in iFR-positive patients (11.9% vs. 0%, p=0.047) and a trend to higher MACE rate (11.9% vs. 4.47% p=0.14), Conclusions The diagnostic accuracy of iFR is low when compared with NIST as the reference for myocardial ischaemia, but it is very high when compared with the combined presence of epicardial stenosis and positive NIST. Therefore, iFR can accurately guide the decision to treat or defer revascularization of intermediate coronary stenoses, being most useful in patients with multivessel CAD and when non-invasive functional data are lacking or discordant with anatomy. Funding Acknowledgement Type of funding source: None

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Assessment of the Loss Map of a Centrifugal Compressor’s External Volute

Volume 2E: Turbomachinery ◽

10.1115/gt2020-14291 ◽

2020 ◽

Author(s):

Thomas Ceyrowsky ◽

Andre Hildebrandt ◽

Martin Heinrich ◽

Rüdiger Schwarze

Keyword(s):

Mach Number ◽

Flow Rate ◽

Numerical Approach ◽

Operating Conditions ◽

Circumferential Velocity ◽

Flow Angle ◽

Absolute Flow ◽

Highly Sensitive ◽

Geometrical Features ◽

Comparison With Experimental Data

Abstract A volute’s loss coefficient is highly sensitive to Mach number, circumferential velocity and flow rate at volute inlet. In case of a backswept impeller, these parameters are coupled to each other. An increased flowrate leads to a steeper absolute flow angle at impeller exit and hence to a decrease of circumferential velocity. The absolute Mach number is also altered. Therefore, in order to investigate the effects of flowrate and flow angle separately, one would have to vary the diffuser width together with the flowrate, keeping the flow angle constant. This corresponds to coupling the volute with aerodynamically similar impellers, designed for higher and lower flowrates. Since this is elaborate, there is no adequate study available in open literature, assessing a volute’s global loss map. In this work, a new numerical approach for the prediction of a volute’s representative loss map is presented: The volute is calculated by means of steady CFD as a standalone component. The inlet boundary conditions are carefully selected by means of 1D and applied together with different diffuser widths. This allows for separate investigation of the impacts of flow angle, flow rate and Mach number. Validation against full stage CFD confirms the applicability of the standalone model. The results exhibit that minimum losses do not necessarily occur at the theoretical matching point but either when the volute is smaller or bigger, depending on the inlet flow angle. Investigations of the loss mechanisms at different operating conditions provide useful guidelines for volute design. Finally, the validity of these study’s findings for volutes with different geometrical features is examined by comparison with experimental data as well as with fullstage CFD.

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Peak calf blood flow estimates are higher with Dohn than with Whitney plethysmograph

Journal of Applied Physiology ◽

10.1152/jappl.1996.81.3.1418 ◽

1996 ◽

Vol 81 (3) ◽

pp. 1418-1422 ◽

Cited By ~ 15

Author(s):

D. N. Proctor ◽

J. R. Halliwill ◽

P. H. Shen ◽

N. E. Vlahakis ◽

M. J. Joyner

Keyword(s):

Blood Flow ◽

Reactive Hyperemia ◽

Arterial Occlusion ◽

Venous Occlusion ◽

Calf Blood Flow ◽

Absolute Flow ◽

Wide Range ◽

Before And After ◽

The Mean ◽

Highly Correlated

Estimates of calf blood flow with venous occlusion plethysmography vary widely between studies, perhaps due to the use of different plethysmographs. Consequently, we compared calf blood flow estimates at rest and during reactive hyperemia in eight healthy subjects (four men and four women) with two commonly used plethysmographs: the mercury-in-silastic (Whitney) strain gauge and Dohn air-filled cuff. To minimize technical variability, flow estimates were compared with a Whitney gauge and a Dohn cuff on opposite calves before and after 10 min of bilateral femoral arterial occlusion. To account for any differences between limbs, a second trial was conducted in which the plethysmographs were switched. Resting flows did not differ between the plethysmographs (P = 0.096), but a trend toward lower values with the Whitney was apparent. Peak flows averaged 37% lower with the Whitney (27.8 +/- 2.8 ml.dl-1.min-1) than with the Dohn plethysmograph (44.4 +/- 2.8 ml.dl-1.min-1; P < 0.05). Peak flow expressed as a multiple above baseline was also lower with the Whitney (10-fold) than with the Dohn plethysmograph (14.5-fold; P = 0.02). Across all flows at rest and during reactive hyperemia, estimates were highly correlated between the plethysmographs in all subjects (r2 = 0.96-0.99). However, the mean slope for the Whitney-Dohn relationship was only 60 +/- 2%, indicating that over a wide range of flows the Whitney gauge estimate was 40% lower than that for the Dohn cuff. These results demonstrate that the same qualitative results can be obtained with either plethysmograph but that absolute flow values will generally be lower with Whitney gauges.

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The Temporalizations of the Absolute Flow of Time-Consciousness

Phaenomenologica - On Time - New Contributions to the Husserlian Phenomenology of Time ◽

10.1007/978-90-481-8766-9_9 ◽

2010 ◽

pp. 169-185 ◽

Cited By ~ 2

Author(s):

Stefano Micali

Keyword(s):

Time Consciousness ◽

Absolute Flow ◽

Flow Of Time ◽

The Absolute

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The role of coronary physiology in contemporary percutaneous coronary interventions.

Current Cardiology Reviews ◽

10.2174/1573403x17666210908114154 ◽

2021 ◽

Vol 17 ◽

Author(s):

Federico Marin ◽

Roberto Scarsini ◽

Dimitrios Terentes-Printzios ◽

Rafail A. Kotronias ◽

Flavio Ribichini ◽

...

Keyword(s):

Functional Assessment ◽

Myocardial Revascularization ◽

Coronary Microcirculation ◽

Coronary Physiology ◽

Catheterization Laboratory ◽

Procedural Time ◽

Coronary Syndromes ◽

Artery Disease ◽

Epicardial Stenosis

: Invasive assessment of coronary physiology has radically changed the paradigm of myocardial revascularization in patients with coronary artery disease. Despite the prognostic improvement associated with ischemia-driven revascularization strategy, functional assessment of angiographic intermediate epicardial stenosis remains largely underused in clinical practice. Multiple tools have been developed or are under development in order to reduce the invasiveness, cost, and extra procedural time associated with the invasive assessment of coronary physiology. Besides epicardial stenosis, a growing body of evidence highlights the role of coronary microcirculation in regulating coronary flow with consequent pathophysiological and clinical and prognostic implications. Adequate assessment of coronary microcirculation function and integrity has then become another component of the decision-making algorithm for optimal diagnosis and treatment of coronary syndromes. This review aims at providing a comprehensive description of tools and techniques currently available in the catheterization laboratory to obtain a thorough and complete functional assessment of the entire coronary tree (both for the epicardial and microvascular compartments).

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Case Study of Multi-Stage Impeller with Guidevane

Volume 2: Fora ◽

10.1115/fedsm2005-77294 ◽

2005 ◽

Author(s):

Takuji Tsugawa

Keyword(s):

Velocity Ratio ◽

Optimum Shape ◽

Hydraulic Efficiency ◽

Mixed Flow ◽

Shape Factors ◽

Flow Angle ◽

Multi Stage ◽

Absolute Flow ◽

Specific Speed

In the previous paper, the optimum meridian profile of impeller was obtained for various specific speed by means of eight shape factors, that is, inlet relative flow angle β1, turning angle Δβ, axial velocity ratio kc = Cm2/Cm1, impeller diameter ratio kd = D1c/D2c, outlet hub-tip ratio ν2, tip solidity σtimp, mid span solidity σcimp and hub solidity σhimp. In this paper, the optimum meridian profile of multi-stage impeller with guidevane was obtained by means of twelve shape factors. The additional four shape factors are guidevane tip solidity σtgv, mid span solidity σcgv, hub solidity σhgv and coefficient of peripheral velocity at impeller inlet or guidevane outlet kCu1c. In the optimum method, the hydraulic efficiency and suction specific speed are calculated by diffusion factor. In the optimum condition, the best hydraulic efficiency or the best suction specific speed is obtained. In the cyclic flow condition of multi-stage impeller with guidevane, the absolute flow velocity of guidevane outlet is equal to that of impeller inlet, and the diameter of guidevane outlet is equal to that of impeller inlet. In this calculation, the diameter of impeller outlet is equal to that of guidevane inlet. The total calculation number of case study is very large, so the number of each parameter is about between four and seven. The best 1000 optimum meridian profiles and the best design parameter are selected for few kinds of specific speed using twelve dimensional optimum method. As the result of this calculation, the optimum meridian profile of multi-stage impeller and guidevane. The more detailed optimum multi-stage mixed flow impeller and guidevane profile is drawn. For, example, the 1000 specific speed is selected for case study of multi-stage mixed flow impeller. At first, the approximate optimum shape factors are present shape factors. And the optimum shape factors which have better efficiency are tried to find near the present shape factors. Then the study of shape factor changes is the objective of this paper.

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Nonlinear Dynamics of Electrokinetic Instabilities

Fluids Engineering ◽

10.1115/imece2005-79845 ◽

2005 ◽

Author(s):

Jonathan D. Posner ◽

Juan G. Santiago

Keyword(s):

Electric Fields ◽

High Speed ◽

Power Spectra ◽

Epifluorescence Microscopy ◽

Bulk Liquid ◽

Sample Stacking ◽

Electrokinetic Instability ◽

Absolute Flow ◽

Electrokinetic Flows ◽

Continuous Power

Electrokinetic instabilities are generated by a coupling of electric fields and ionic conductivity gradients. This coupling results in an electric body force in the bulk liquid that can generate temporal, convective, and absolute flow instabilities. In this work, we perform a parametric experimental study of convective instabilities in cross-shaped microchannels using epifluorescence microscopy and high speed digital imaging. We report temporal power spectra and spatiotemporal maps as a function of the applied field. The spectral analyses reveal that disturbances induced by electrokinetic instability are purely sinuous at the onset of instability and exhibit higher-order harmonics, frequency bifurcations, and continuous power spectra with increasing electric Rayleigh number. Electrokinetic instabilities (EKI) in cross-shaped channels are relevant to injections for field amplified sample stacking, electrokinetic flows at the intersections in multi-dimensional assay devices, and systems with indeterminate sample chemistry.

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Influence of Heart Rate and Epicardial Stenosis Severity on Cardiac Contractility Under Concomitant Microvascular Disease in a Porcine Model

ASME 2011 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2011-53512 ◽

2011 ◽

Author(s):

Srikara V. Peelukhana ◽

Kranthi K. Kolli ◽

William Gottliebson ◽

Massoud Leesar ◽

Tarek Helmy ◽

...

Keyword(s):

Heart Rate ◽

Guide Wire ◽

Cardiac Contractility ◽

Microvascular Disease ◽

In Vivo Experiments ◽

Stenosis Severity ◽

Yorkshire Pigs ◽

Epicardial Stenosis ◽

Dynamic Variables

Invasive guide wire methods to assess functional severity of coronary stenosis are affected by dynamic variables like heart rate (HR), contractility, epicardial stenosis (AS) and blood pressure. The interdependence of these factors is also influenced by the presence of concomitant microvascular disease (CMVD). The purpose of this study is to assess the variation in contractility under varying HR and AS in the presence of CMVD. In vivo experiments were performed on seven Yorkshire pigs. It was found that, in the presence of concomitant microvascular disease (CMVD), for lower AS (<50%) contractility increases for HR<120 bpm while it marginally decreases for HR>120 bpm. However, for higher AS (>50%), contractility decreases for both HR<120 bpm and HR>120 bpm.

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Quantitating error in blood flow measurements with radioactive microspheres

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1989.257.1.h280 ◽

1989 ◽

Vol 257 (1) ◽

pp. H280-H288 ◽

Cited By ~ 10

Author(s):

R. E. Austin ◽

W. W. Hauck ◽

G. S. Aldea ◽

A. E. Flynn ◽

D. L. Coggins ◽

...

Keyword(s):

Blood Flow ◽

Accurate Determination ◽

Relative Distribution ◽

Experimental Conditions ◽

Flow Measurements ◽

Sources Of Error ◽

Absolute Flow ◽

Anesthetized Dogs ◽

The Difference ◽

Blood Flow Measurements

Accurate determination of the reproducibility of measurements using the microsphere technique is important in assessing differences in blood flow to different organs or regions within organs, as well as changes in perfusion under various experimental conditions. The sources of error of the technique are briefly reviewed. In addition, we derived a method for combining quantifiable sources of error into a single estimate that was evaluated experimentally by simultaneously injecting eight or nine sets of microspheres (each with a different radionuclide label) into four anesthetized dogs. Each nuclide was used to calculate blood flow in 145–190 myocardial regions. We compared each flow determination (using a single nuclide label) with a weighted mean for the piece (based on the remaining nuclides). The difference was defined as “measured” error. In all, there were a total of 5,975 flow observations. We compared measured error with theoretical estimates based on the Poisson error of radioactive disintegration and microsphere entrapment, nuclide separation error, and reference flow error. We found that combined estimates based on these sources completely accounted for measured error in the relative distribution of microspheres. In addition, our estimates of the error in measuring absolute flows (which were established using microsphere reference samples) slightly, but significantly, underestimated measured error in absolute flow.

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