Functional Diagnosis of Coronary Artery Stenoses Using Pressure Drop Coefficient: A Pilot Study in Humans

2011 ◽  
Author(s):  
Kranthi K. Kolli ◽  
Mohamed Effat ◽  
Imran Arif ◽  
Tarek Helmy ◽  
Massoud Leesar ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Dynamic Pressure ◽  
Doppler Velocity ◽  
Diagnostic Parameter ◽  
Functional Index ◽  
Functional Diagnosis ◽  
Dual Sensor ◽  
Coronary Artery Stenoses ◽  
Stenosis Severity ◽  
Functional Diagnostic

Optimization of cut-off values for diagnostic parameters in determining stenosis severity depends on coupling functional (hemodynamic) and anatomical data. In this study, we sought to investigate the functional diagnostic parameter (CDP; the ratio of trans-stenotic pressure drop to distal dynamic pressure) by correlating with FFR (ratio of distal to proximal pressure of a stenotic section) and CFR (ratio of hyperemic blood flow velocity to that of resting condition). A 0.014-inch dual sensor (pressure and Doppler velocity) guidewire was used in 9 patients to obtain pressure drop and velocity at hyperemia. Functional index CDP was assessed from measured hyperemic pressure drop and velocity. CDP correlated linearly and significantly with FFR and CFR. Indicating that, measurements of CDP can provide a better assessment of stenosis severity.

Diagnostic Uncertainties During Assessment of Serial Coronary Stenoses: An In Vitro Study

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Gavin A. D’Souza ◽  
Srikara V. Peelukhana ◽  
Rupak K. Banerjee
Keyword(s):  
Pressure Drop ◽  
Dynamic Pressure ◽  
Clinical Intervention ◽  
In Vitro Study ◽  
Gray Zone ◽  
Diagnostic Parameter ◽  
Fractional Flow ◽  
Flow Reserve ◽  
Stenosis Severity

Currently, the diagnosis of coronary stenosis is primarily based on the well-established functional diagnostic parameter, fractional flow reserve (FFR: ratio of pressures distal and proximal to a stenosis). The threshold of FFR has a “gray” zone of 0.75–0.80, below which further clinical intervention is recommended. An alternate diagnostic parameter, pressure drop coefficient (CDP: ratio of trans-stenotic pressure drop to the proximal dynamic pressure), developed based on fundamental fluid dynamics principles, has been suggested by our group. Additional serial stenosis, present downstream in a single vessel, reduces the hyperemic flow, Q˜h, and pressure drop, Δp˜, across an upstream stenosis. Such hemodynamic variations may alter the values of FFR and CDP of the upstream stenosis. Thus, in the presence of serial stenoses, there is a need to evaluate the possibility of misinterpretation of FFR and test the efficacy of CDP of individual stenoses. In-vitro experiments simulating physiologic conditions, along with human data, were used to evaluate nine combinations of serial stenoses. Different cases of upstream stenosis (mild: 64% area stenosis (AS) or 40% diameter stenosis (DS); intermediate: 80% AS or 55% DS; and severe: 90% AS or 68% DS) were tested under varying degrees of downstream stenosis (mild, intermediate, and severe). The pressure drop-flow rate characteristics of the serial stenoses combinations were evaluated for determining the effect of the downstream stenosis on the upstream stenosis. In general, Q˜h and Δp˜ across the upstream stenosis decreased when the downstream stenosis severity was increased. The FFR of the upstream mild, intermediate, and severe stenosis increased by a maximum of 3%, 13%, and 19%, respectively, when the downstream stenosis severity increased from mild to severe. The FFR of a stand-alone intermediate stenosis under a clinical setting is reported to be ∼0.72. In the presence of a downstream stenosis, the FFR values of the upstream intermediate stenosis were either within (0.77 for 80%–64% AS and 0.79 for 80%–80% AS) or above (0.88 for 80%–90% AS) the “gray” zone (0.75–0.80). This artificial increase in the FFR value within or above the “gray” zone for an upstream intermediate stenosis when in series with a clinically relevant downstream stenosis could lead to misinterpretation of functional stenosis severity. In contrast, a distinct range of CDP values was observed for each case of upstream stenosis (mild: 8–10; intermediate: 47–54; and severe: 130–155). The nonoverlapping range of CDP could better delineate the effect of the downstream stenosis from the upstream stenosis and allow for the accurate diagnosis of the functional severity of the upstream stenosis.

Assessment of Aortic Stenosis Severity Using Pressure Drop Coefficient: A Retrospective Study in Humans

2013 ◽  
Author(s):  
Anup K. Paul ◽  
Mohamed Effat ◽  
Jason J. Paquin ◽  
Rupak K. Banerjee
Keyword(s):  
Retrospective Study ◽  
Pressure Drop ◽  
Aortic Stenosis ◽  
Clinical Decision Making ◽  
Dynamic Pressure ◽  
Clinical Decision ◽  
Diagnostic Parameters ◽  
Stenosis Severity ◽  
Preliminary Study ◽  
A Prospective Study

Accurate assessment of the stenosis severity is critical in patients with aortic stenosis (AS). The ambiguities and reduced sensitivities of the current diagnostic parameters can result in sub-optimal clinical decision making. In this preliminary study, we investigate the functional diagnostic parameter CDP (ratio of the transvalvular pressure drop to the proximal dynamic pressure) for the assessment of AS severity by correlating with the current diagnostic parameters. CDP was calculated using diagnostic parameters obtained from retrospective chart reviews. CDP values were calculated independently from Doppler and catheterization measurements. CDP exhibited better correlation with transvalvular pressure drop and jet velocity simultaneously, than when correlated independently with the same diagnostic parameters. CDP increases with increasing AS severity, which is consistent with hydrodynamic principles. This retrospective study is a prelude to a prospective study to evaluate CDP for AS severity assessment.

Functional and Anatomical Diagnosis of Coronary Artery Stenoses: A Retrospective Study in Humans

2012 ◽  
Author(s):  
Kranthi K. Kolli ◽  
Mohamed Effat ◽  
Imran Arif ◽  
Tarek Helmy ◽  
Massoud Leesar ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Dynamic Pressure ◽  
Microvascular Disease ◽  
Flow Coefficient ◽  
Fractional Flow ◽  
Throat Region ◽  
Flow Reserve ◽  
Stenosis Severity ◽  
Lesion Flow Coefficient ◽  
Hemodynamic Information

Fractional flow reserve (FFR: ratio of distal to proximal pressure of a stenotic section) is used to evaluate hemodynamic significance of epicardial stenosis. However, FFR and coronary flow reserve (CFR: ratio of hyperemic blood velocity to that of resting condition) are used in conjunction to evaluate combination of both epicardial and microvascular disease. It has been proposed that optimization of cutoff values for diagnostic parameters in determining stenosis severity depends on coupling functional (pressure and velocity) and anatomical data (% area stenosis). We hypothesize that, pressure drop coefficient (CDP: the ratio of trans-stenotic pressure drop to distal dynamic pressure) which has the functional information of pressure and velocity in its formulation correlates significantly with FFR and CFR, and lesion flow coefficient (LFC: ratio of % area stenoses to CDP at throat region) which combines both functional and anatomical (% area stenoses) information in its formulation correlates significantly with FFR, CFR and % area stenosis. We retrospectively analyzed the hemodynamic information from Meuwissen et al [3] to test this hypothesis. It was observed that, CDP, a functional index based on pressure drop and velocity, correlated linearly and significantly with FFR and CFR. And, LFC (combined functional and anatomic parameter) also correlated significantly with FFR, CFR (both hemodynamic endpoints) and % area stenosis (anatomic endpoint).

Abstract 13539: Physiological Basis of Discordance Between Coronary Flow Reserve and Hyperemic Microvascular Resistance to Evaluate Coronary Microvascular Dysfunction in Patients Without Atherosclerotic Obstruction

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Kenshi Yamanaga ◽  
Kenichi Tsujita ◽  
Naohiro Komura ◽  
Kenji Sakamoto ◽  
Masanobu Ishii ◽  
...  
Keyword(s):  
Coronary Flow Reserve ◽  
Coronary Flow ◽  
Doppler Velocity ◽  
Physiological Basis ◽  
Group 4 ◽  
Flow Reserve ◽  
Dual Sensor ◽  
Group 2 ◽  
Coronary Obstruction ◽  
Group 1

Introduction: Although coronary flow reserve (CFR) has been the only physiological way to evaluate the coronary microvascular (MV) function until recently, hyperemic MV resistance (hMR) have been developed as a newer modality measuring directly coronary MV function. Discordance between CFR and hMR may reflect various coronary hemodynamic situations. Hypothesis: Simultaneous measurement of CFR/hMR in pts without coronary obstruction could provide us deeper appreciation of hemodynamic functional alterations in coronary microvasculature. Methods: In 44 pts without coronary stenosis (diameter stenosis >50%), CFR and hMR were measured utilizing a dual sensor (Doppler velocity and pressure)-equipped guidewire. To evaluate coronary MV hemodynamics, pts were categorized into four CFR/hMR quadrants using a cutoff values of CFR≥2.0 and hMR<1.7 (median value of all study subjects) (Figure). Results: Discordance results between CFR/hMR was present in 39% of patients (17 of 44), with CFR≥2.0 and hMR≥1.7 in 30% (13 of 44) and CFR<2.0 and hMR<1.7 in 9% (4 of 44). There were significantly negative correlation between hMR and hyperemic average peak velocity (APV) (r=-0.73, p<0.0001), CFR and baseline APV (r=-0.66, p<0.001) despite no correlation between CFR and hyperemic APV (r=0.25, p=0.1). Baseline APV and hyperemic APV were significantly different among these groups (baseline APV; group 2 vs. group 3, 12.0±5.7 vs. 30.5±7.2, p=0.02, group 2 vs. group 4, 12.0±5.7 vs. 21.3±8.5, p=0.002, hyperemic APV; group 1 vs. group 4; 51.2±10.4 vs. 28.7±10.2, p<0.0001, group 1 vs. group 2, 51.2±10.4 vs. 32.5±13.6, p=0.03). Four CFR/hMR quadrants thus represent 4 different types of coronary blood flow-perfusion pressure relationship (Figure). Conclusions: In pts without coronary obstruction, CFR was related to coronary autoregulation state and hMR to hyperemic state. Simultaneous CFR/hMR measurement might provide new physiological insight about coronary MV hemodynamics.

scholarly journals Vascular Stenosis Asymmetry Influences Considerably Pressure Gradient and Flow Volume

2016 ◽  
pp. 63-69 ◽  
Author(s):  
L. NOVAKOVA ◽  
J. KOLINSKY ◽  
J. ADAMEC ◽  
J. KUDLICKA ◽  
J. MALIK
Keyword(s):  
Pressure Drop ◽  
Flow Volume ◽  
Hemodynamic Changes ◽  
Flow Measurements ◽  
Stenosis Severity ◽  
Vascular Stenosis ◽  
Particle Imaging ◽  
Different Levels ◽  
Volume Decrease

Vascular stenosis is often described only by its percentage in both clinical and scientific praxis. Previous studies gave inconclusive results regarding the effect of stenosis eccentricity on its hemodynamic effect. The aim of this experimental study was to investigate and quantify the effect of stenosis severity and eccentricity on the pressure drop. A combination of pressure and flow measurements by Particle Imaging Velocimetry (PIV) method was used. Models of the same stenosis significance but with different levels of eccentricity were studied in vitro by PIV. This study has shown that stenosis asymmetry is associated with more profound pressure drop and flow volume decrease. On the contrary, pressure drop and flow volume decrease were not further significantly influenced by the level of asymmetry. Hemodynamic changes associated with stenosis eccentricity must be taken into account in both clinical and scientific studies.

Methodology for Hemodynamic Assessment of a Three-Dimensional Printed Patient-Specific Vascular Test Device

2019 ◽  
Vol 13 (3) ◽  
Author(s):  
Gavin A. D'Souza ◽  
Michael D. Taylor ◽  
Rupak K. Banerjee
Keyword(s):  
Pressure Drop ◽  
3D Printing ◽  
Medical Devices ◽  
Velocity Ratio ◽  
Three Dimensional ◽  
Patient Specific ◽  
Test Device ◽  
Dimensionless Pressure ◽  
Hemodynamic Assessment ◽  
Stenosis Severity

Assessing hemodynamics in vasculature is important for the development of cardiovascular diagnostic parameters and evaluation of medical devices. Benchtop experiments are a safe and comprehensive preclinical method for testing new diagnostic endpoints and devices within a controlled environment. Recent advances in three-dimensional (3D) printing have enhanced benchtop tests by allowing generation of patient-specific and pathophysiologic conditions. We used 3D printing, coupled with image processing and computer-aided design (CAD), to develop a patient-specific vascular test device from clinical data. The proximal pulmonary artery (PA) tree including the main, left, and right pulmonary arteries, with a stenosis within the left PA was selected as a representative anatomy for developing the vascular test device. Three test devices representing clinically relevant stenosis severities, 90%, 80%, and 70% area stenosis, were evaluated at different cardiac outputs (COs). A mock circulatory loop (MCL) generating pathophysiologic pulmonary pressure and flow was used to evaluate the hemodynamics within the devices. The dimensionless pressure drop–velocity ratio characteristic curves for the three stenosis severities were obtained. At a fixed CO, the dimensionless pressure drop increased nonlinearly with an increase in (a) the velocity ratio for a fixed stenosis severity and (b) the stenosis severity at a specific velocity ratio. The dimensionless pressure drop observed in vivo was similar (within 1%) to that measured in moderate area stenosis of 70% because both flows were viscous dominated. The hemodynamics of the 3D printed test device can be used for evaluating diagnostic endpoints and medical devices in a preclinical setting under realistic conditions.

Aerodynamic Torque Acting on a Butterfly Valve. Comparison and Choice of a Torque Coefficient

1999 ◽  
Vol 121 (4) ◽  
pp. 914-917 ◽  
Author(s):  
C. Solliec ◽  
F. Danbon
Keyword(s):  
Pressure Drop ◽  
Static Pressure ◽  
Fluid Dynamic ◽  
Dynamic Pressure ◽  
Low Cost ◽  
Normalization Method ◽  
Pressure Drops ◽  
Torque Coefficient ◽  
Aerodynamic Torque ◽  
Valve Pressure

Most technological devices use butterfly valves to check the flow rate and speed, through piping. Their main advantages are their low cost, their mechanical suitability for fast operation, and their small pressure drops when they are fully open. The fluid dynamic torque about the axis of large valves has to be considered as the actuator could be overstrained. This torque is generally defined using a nondimensional coefficient KT, in which the static pressure drop created by the valve is used for normalization. When the valve is closed downstream of an elbow, the valve pressure drop is not well defined. Thus, the classic normalization method gives many ambiguities. To avoid the use of the pressure drop, we define another torque coefficient CT in which the dynamic pressure of the flow is the normalization factor instead of the pressure drop. Advantages and drawbacks of each normalization method are described in the following.

scholarly journals Characterization of ultra low frequency (ULF) pulsations and the investigation of their possible source

2009 ◽  
Vol 27 (8) ◽  
pp. 3287-3296 ◽  
Author(s):  
S. H. Mthembu ◽  
S. B. Malinga ◽  
A. D. M. Walker ◽  
L. Magnus
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Temporal Structure ◽  
Sudden Change ◽  
Low Frequency ◽  
Hf Radar ◽  
Doppler Velocity ◽  
Full Field ◽  
Spectral Techniques ◽  
Field Lines

Abstract. In this paper we present the results from the observation of ultra low frequency (ULF) pulsations in the Doppler velocity data from SuperDARN HF radar located at Goose Bay (61.94° N, 23.02° E, geomagnetic). Fourier spectral techniques were used to determine the spectral content of the data and the results show Pc 5 ULF pulsations (with a frequency range of 1 to 4 mHz) where the magnetic field lines were oscillating at discrete frequencies of about 1.3 and 1.9 mHz. These pulsations are classified as field lines resonance (FLR) since the 1.9 mHz component exhibited an enhancement in amplitude with an associated phase change of approximately 180° across a resonance latitude of 71.3°. The spatial and temporal structure of the ULF pulsations was examined by investigating their instantaneous amplitude which was calculated as the amplitude of the analytic signal. The results presented a full field of view which exhibit pulsations activity simultaneously from all beams. This representation shows that the peak amplitude of the 1.9 mHz component was observed over the longitudinal range of 13°. The temporal structure of the pulsations was investigated from the evolution of the 1.9 mHz component and the results showed that the ULF pulsations had a duration of about 1 h. Wavelet analysis was used to investigate solar wind as a probable source of the observed ULF pulsations. The time delay compared well with the solar wind travel time estimates and the results suggest a possible link between the solar wind and the observed pulsations. The sudden change in dynamic pressure also proved to be a possible source of the observed ULF pulsations.

scholarly journals Experimental Investigation of the Effects of Arterial Geometries in Different Severities of Symmetrical Stenosis on Pressure Drop and Pump Power

2021 ◽  
Author(s):  
Fatin SONMEZ ◽  
Orhan YILDIRIM ◽  
Sendogan KARAGOZ ◽  
Fuat GUNDOGDU
Keyword(s):  
Pressure Drop ◽  
Test Area ◽  
Differential Pressure ◽  
Arterial Stenosis ◽  
Peristaltic Pump ◽  
Outlet Pressure ◽  
Stenosis Severity ◽  
High Pulse ◽  
Human Arteries ◽  
Pump Inlet

Abstract Biomedical studies is among the multidisciplinary studies attracting most interest in recent years. Blood and vessel interactions and consequent hemodynamic effects cause cardiovascular diseases. A testing setup constituted by a peristaltic pump (similar to the heart mechanism) system was installed. The purpose of the experimental study presented is to investigate the effect, pressure drop, peristaltic pump inlet and outlet pressure and most importantly, the amount of power consumed by the peristaltic pump regarding arterial stenosis severity with varying areal stenosis percentages. The tests were performed for the pulse values from 54 to 168 bpm by setting up models with 0%, 60%, 70% and 80% symmetrical stenosis severities. In the study, the pressure difference in the test area increased concomitantly with elevated pulse value and increased stenosis severity. This situation revealed that as the intensity of narrowing increases in vessels, the narrowing space differential pressure increases, and this amount increases even more with increased exertion. The pressure at the peristaltic pump outlet increased concomitantly with elevated pulse value and increased stenosis severity. The peristaltic pump overworked to overcome the increased differential pressure related to the increased pulse value and stenosis severity. This result of the experimental data reveals the necessity to avoid activities requiring high pulse in human arteries similarly with a high percentage of stenosis.

A Hemodynamic Comparison of Myocardial Bridging and Coronary Atherosclerotic Stenosis: A Computational Model with Experimental Evaluation

2020 ◽  
Author(s):  
Mohammadali Sharzehee ◽  
Yasamin Seddighi ◽  
Eugene A. Sprague ◽  
Ender A. Finol ◽  
Hai-Chao Han
Keyword(s):  
Pressure Drop ◽  
Experimental Results ◽  
Cfd Modeling ◽  
Patient Specific ◽  
Flow Loop ◽  
Myocardial Bridging ◽  
Atherosclerotic Stenosis ◽  
Stenosis Severity ◽  
The Difference

Abstract Myocardial bridging (MB) and coronary atherosclerotic stenosis can impair coronary blood flow and may cause myocardial ischemia or even stoke. It remains unclear how MB and stenosis are similar or different regarding their impacts on coronary hemodynamics. The purpose of this study was to compare the hemodynamic effects of MB and stenosis using experimental and computational fluid dynamics (CFD) approaches. For CFD modeling, three MB patients with different levels of lumen obstruction such as mild, moderate, and severe were selected. Patient-specific left anterior descending coronary artery models were reconstructed from biplane angiograms. For each MB patient, the virtually healthy and stenotic models were also simulated for comparison. In addition, an in vitro flow-loop was developed to evaluate the model-predicted pressure drop. The CFD modeling results demonstrated that the difference between MB and stenosis increased with increasing MB/stenosis severity and flow rate. Experimental results showed that increasing the MB length (by 140%) only had significant impact on the pressure drop in the severe MB (39% increase at the exercise). However, increasing the stenosis length dramatically increased the pressure drop in both moderate and severe stenoses at all flow rates (31% and 93% increase at the exercise, respectively). Both CFD and experimental results confirmed that the MB had a higher maximum and a lower mean pressure drop in comparison with the stenosis, regardless of MB/stenosis severity. A better understanding of MB and stenosis may improve the therapeutic strategies in coronary disease patients and prevent acute coronary syndromes.

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