scholarly journals Impact of Inflow Boundary Conditions on the Calculation of CT-Based FFR

Fluids ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 60 ◽  
Author(s):  
Ernest Lo ◽  
Leon Menezes ◽  
Ryo Torii
Keyword(s):  
Boundary Conditions ◽  
Coronary Arteries ◽  
Three Dimensional ◽  
Patient Specific ◽  
Fractional Flow ◽  
Anatomical Models ◽  
Diastolic Phase ◽  
Flow Reserve ◽  
Population Average ◽  
The Impact

Background: Calculation of fractional flow reserve (FFR) using computed tomography (CT)-based 3D anatomical models and computational fluid dynamics (CFD) has become a common method to non-invasively assess the functional severity of atherosclerotic narrowing in coronary arteries. We examined the impact of various inflow boundary conditions on computation of FFR to shed light on the requirements for inflow boundary conditions to ensure model representation. Methods: Three-dimensional anatomical models of coronary arteries for four patients with mild to severe stenosis were reconstructed from CT images. FFR and its commonly-used alternatives were derived using the models and CFD. A combination of four types of inflow boundary conditions (BC) was employed: pulsatile, steady, patient-specific and population average. Results: The maximum difference of FFR between pulsatile and steady inflow conditions was 0.02 (2.4%), approximately at a level similar to a reported uncertainty level of clinical FFR measurement (3–4%). The flow with steady BC appeared to represent well the diastolic phase of pulsatile flow, where FFR is measured. Though the difference between patient-specific and population average BCs affected the flow more, the maximum discrepancy of FFR was 0.07 (8.3%), despite the patient-specific inflow of one patient being nearly twice as the population average. Conclusions: In the patients investigated, the type of inflow boundary condition, especially flow pulsatility, does not have a significant impact on computed FFRs in narrowed coronary arteries.

Patient-specific anatomical models in human physiology

2015 ◽  
Vol 30 (3) ◽  
Author(s):  
Yuri V. Vassilevski ◽  
Alexander A. Danilov ◽  
Sergey S. Simakov ◽  
Timur M. Gamilov ◽  
Yuri A. Ivanov ◽  
...  
Keyword(s):  
Human Physiology ◽  
3D Reconstruction ◽  
Coronary Arteries ◽  
Numerical Evaluation ◽  
Patient Specific ◽  
Medical Applications ◽  
Fractional Flow ◽  
Anatomical Models ◽  
Physiological Processes ◽  
Flow Reserve

AbstractPatient-specific simulations of human physiological processes remain the challenge for many years. Detailed 3D reconstruction of body anatomical parts on the basis of medical images is an important stage of individualized simulations in physiology. In this paper we present and develop the methods and algorithms for construction of patient-specific discrete geometric models. These models are represented by anatomically correct computational meshes. Practical use of these methods is demonstrated for two important medical applications: numerical evaluation of fractional flow reserve in coronary arteries and electrocardiography simulation

Abstract 12632: Impact of Systolic Pressure Response on Measurement of Fractional Flow Reserve

Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Tomoyuki Ikeda ◽  
Masafumi Ueno ◽  
Shinichiro Ikuta ◽  
Kosuke Fujita ◽  
Masakazu Yasuda ◽  
...  
Keyword(s):  
Coronary Arteries ◽  
Fractional Flow Reserve ◽  
Cardiac Cycle ◽  
Systolic Pressure ◽  
Pressure Response ◽  
The Other ◽  
Fractional Flow ◽  
Diastolic Phase ◽  
Flow Reserve ◽  
Significant Difference

Background: Fractional flow reserve (FFR) is calculated as the ratio between distal coronary pressure(Pd)and aortic pressure(Pa)during whole cardiac cycle at stable hyperemia. In clinical practice, we experience various Pd wave pattern during hyperemia, such as decreasing equally in systolic and diastolic phase, or mainly decreasing in diastolic phase. Purpose: The aim of the study was to evaluate the impact of systolic and diastolic pressure response during hyperemia in patients with coronary stenosis and an FFR of less than 0.8. Methods: A total of 35 patients (40 stenosis)had FFR of less than 0.8 were enrolled. FFR measurements were performed using a standard technique. Based on Pa and Pd wave forms, the decreasing area in systolic and diastolic were calculated by integrating Pa-Pd pressure gradient during hyperemia using the RadiView2.2 software. %Sys value was defined as the percentage of delta systolic area during the whole cardiac cycle (Figure). The results of %Sys values were divided into tertiles to evaluate the most significant factors for systolic pressure response. Results: Vessel distribution was as follows: LAD (60%), CX (20%) and RCA (20%). There was a significant difference of vessel distribution in coronary arteries in the upper tertile compared with the other two tertiles of %Sys values (p=0.028). However, the other factors such as FFR value, lesion length and severity, history of diabetes mellitus and previous myocardial infraction were not affected by the %Sys values. In addition, there was a significant difference of %Sys values among three major coronary arteries (LAD 49.4±18.5%, CX 81.5±38.7%, RCA 67.5±20.2%, p=0.006). %Sys values were significantly higher in non-LAD lesions compared with LAD lesions (74.5±30.7% vs 49.4±18.5%, p=0.003). Conclusions: There was a significant difference of decreasing pattern of Pd wave during hyperemia among the three coronary arteries. These findings suggest that iFR might not be accurate in non-LAD lesion.

Assessment of Invasive Fractional Flow Reserve Procedures Using Computational Fluid Dynamics

2020 ◽  
Author(s):  
Yasser Abuouf ◽  
Muhamed Albadawi ◽  
Shinichi Ookawara ◽  
Mahmoud Ahmed
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Pressure Drop ◽  
Fractional Flow Reserve ◽  
Treatment Plan ◽  
Three Dimensional ◽  
Patient Specific ◽  
Concomitant Treatment ◽  
Fractional Flow ◽  
Flow Reserve

Abstract Coronary artery disease is the abnormal contraction of heart supply blood vessel. It may lead to major consequences such as heart attack and death. This narrowing in the coronary artery limits the oxygenated blood flow to the heart. Thus, diagnosing its severity helps physicians to select the appropriate treatment plan. Fractional Flow Reserve (FFR) is one of the most accurate methods to pinpoint the stenosis severity. The advantages of FFR are high accuracy, immediate estimation of the severity of the stenosis, and concomitant treatment using balloon or stent. Nevertheless, the main disadvantage of the FFR is being an invasive procedure that requires an incision under anesthesia. Moreover, inserting the guidewire across the stenosis may result in a ‘tight-fit’ between the vessel lumen and the guidewire. This may cause an increase in the measured pressure drop, leading to a false estimation of the blood flow parameters. To estimate the errors in diagnosis procedures, a comprehensive three-dimensional model blood flow along with guidewire is developed. Reconstructed three-dimensional coronary artery geometry from a patient-specific scan is used. Blood is considered non-Newtonian and the flow is pulsatile. The comprehensive model is numerically simulated using boundary conditions. Based on the predicted results, the ratio between pressure drop and distal dynamic pressure (CDP) is studied. The predicted results for each case are compared with the control case (the case without guidewire) and analyzed. It was found that simulating the model by placing the guidewire at a full position prior to the simulation leads to an overestimation of the CDP as it increases by 34.3%. However, simulating the procedure of guidewire insertion is more accurate. It shows that the CDP value increases by 7%.

An Outflow Boundary Condition Model for Noninvasive Prediction of Fractional Flow Reserve in Diseased Coronary Arteries

2018 ◽  
Vol 140 (4) ◽  
Author(s):  
Iyad A. Fayssal ◽  
Fadl Moukalled ◽  
Samir Alam ◽  
Hussain Isma'eel
Keyword(s):  
Boundary Condition ◽  
Coronary Arteries ◽  
Fractional Flow Reserve ◽  
Physiological Parameters ◽  
Arterial System ◽  
Patient Specific ◽  
Fractional Flow ◽  
Condition Model ◽  
Flow Reserve ◽  
Boundary Condition Model

This paper reports on a new boundary condition formulation to model the total coronary myocardial flow and resistance characteristics of the myocardial vascular bed for any specific patient when considered for noninvasive diagnosis of ischemia. The developed boundary condition model gives an implicit representation of the downstream truncated coronary bed. Further, it is based on incorporating patient-specific physiological parameters that can be noninvasively extracted to account for blood flow demand to the myocardium at rest and hyperemic conditions. The model is coupled to a steady three-dimensional (3D) collocated pressure-based finite volume flow solver and used to characterize the “functional significance” of a patient diseased coronary artery segment without the need for predicting the hemodynamics of the entire arterial system. Predictions generated with this boundary condition provide a deep understanding of the inherent challenges behind noninvasive image-based diagnostic techniques when applied to human diseased coronary arteries. The overall numerical method and formulated boundary condition model are validated via two computational-based procedures and benchmarked with available measured data. The newly developed boundary condition is used via a designed computational methodology to (a) confirm the need for incorporating patient-specific physiological parameters when modeling the downstream coronary resistance, (b) explain the discrepancies presented in the literature between measured and computed fractional flow reserve (FFRCT), and (c) discuss the current limitations and future challenges in shifting to noninvasive assessment of ischemia.

scholarly journals Effect of guidewire insertion in fractional flow reserve procedure for real geometry using computational fluid dynamics

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Yasser Abuouf ◽  
Muhamed AlBadawi ◽  
Shinichi Ookawara ◽  
Mahmoud Ahmed
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Fractional Flow Reserve ◽  
Treatment Plan ◽  
Three Dimensional ◽  
Patient Specific ◽  
Flow Ratio ◽  
Fractional Flow ◽  
Flow Reserve ◽  
Actual Flow

Abstract Background Coronary artery disease is an abnormal contraction of the heart supply blood vessel. It limits the oxygenated blood flow to the heart. Thus, diagnosing its severity helps physicians to select the appropriate treatment plan. Fractional flow reserve (FFR) is the most accurate method to pinpoint the stenosis severity. However, inserting the guidewire across stenosis may cause a false overestimation of severity. Methods To estimate the errors due to guidewire insertion, reconstructed three-dimensional coronary artery geometry from a patient-specific scan is used. A comprehensive three-dimensional blood flow model is developed. Blood is considered non-Newtonian and the flow is pulsatile. The model is numerically simulated using realistic boundary conditions. Results The FFR value is calculated and compared with the actual flow ratio. Additionally, the ratio between pressure drop and distal dynamic pressure (CDP) is studied. The obtained results for each case are compared and analyzed with the case without a guidewire. It was found that placing the guidewire leads to overestimating the severity of moderate stenosis. It reduces the FFR value from 0.43 to 0.33 with a 23.26% error compared to 0.44 actual flow ratio and the CDP increases from 5.31 to 7.2 with a 35.6% error. FFR value in mild stenosis does not have a significant change due to placing the guidewire. The FFR value decreases from 0.83 to 0.82 compared to the 0.83 actual flow ratio. Conclusion Consequently, physicians should consider these errors while deciding the treatment plan.

Three-Dimensional Simulations in Glenn Patients: Clinically Based Boundary Conditions, Hemodynamic Results and Sensitivity to Input Data

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
G. Troianowski ◽  
C. A. Taylor ◽  
J. A. Feinstein ◽  
I. E. Vignon-Clementel
Keyword(s):  
Pulmonary Artery ◽  
Boundary Conditions ◽  
Clinical Data ◽  
Power Loss ◽  
Input Data ◽  
Three Dimensional ◽  
Patient Specific ◽  
Mean Flow ◽  
Fontan Surgery ◽  
The Impact

While many congenital heart defects can be treated without significant long term sequelae, some achieve successful palliation as their definitive endpoints. The single-ventricle defect is one such defect and leaves the child with only one operational ventricle, requiring the systemic and the pulmonary circulations to be placed in series through several operations performed during early childhood. Numerical simulations may be used to investigate these hemodynamic conditions and their relation to post-operative sequelae; however, they rely heavily on boundary condition prescription. In this study, we investigate the impact of hemodynamic input data uncertainties on simulation results. Imaged-based patient-specific models of the multi-branched pulmonary arteries and superior vena cava were built for five cavopulmonary connection (i.e. Glenn) patients. Magnetic resonance imaging and catheterization data were acquired for each patient prior to their Fontan surgery. Inflow and outflow boundary conditions were constructed to match available clinical data and resulted in the development of a framework to incorporate these types of clinical data into patient-specific simulations. Three-dimensional computational fluid dynamics simulations were run and hemodynamic indicators were computed. Power loss was low (and efficiency very high) and a linear correlation was found between power loss and cardiac index among the five patients. Other indicators such as low wall shear stress were considered to better characterize these patients. Flow was complex and oscillatory near the anastomosis, and laminar in the smaller branches. While common trends were seen among patients, results showed differences among patients, especially in the 3D maps, strengthening the importance of patient-specific simulations. A sensitivity analysis was performed to investigate the impact of input data (clinical and modeling) to construct boundary conditions on several indicators. Overall, the sensitivity of the output indicators to the input data was small but non-negligible. The sensitivity of commonly used hemodynamic indicators to compare patients is discussed in this context. Power efficiency was much more sensitive to pressure variation than power loss. To increase the precision of such indicators, mean flow split between right and left lungs needs to be measured with more accuracy with higher priority than refining the model of how the flow is distributed on average among the smaller branches. Although ±10% flow split imprecision seemed reasonable in terms of patient comparison, this study suggests that the common practice of imposing a right pulmonary artery/left pulmonary artery flow split of 55%/45% when performing patient specific simulations should be avoided. This study constitutes a first step towards understanding the hemodynamic differences between pre- and post Fontan surgery, predicting these differences, and evaluating surgical outcomes based on preoperative data.

scholarly journals A Computational Analysis of the Influence of a Pressure Wire in Evaluating Coronary Stenosis

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 165
Author(s):  
Jie Yi ◽  
Fang-Bao Tian ◽  
Anne Simmons ◽  
Tracie Barber
Keyword(s):  
Coronary Stenosis ◽  
Severe Case ◽  
Patient Specific ◽  
Fractional Flow ◽  
Ideal Model ◽  
Coronary Pressure ◽  
Flow Reserve ◽  
Pressure Wire ◽  
Physical Presence ◽  
The Difference

Cardiovascular disease is one of the world’s leading causes of morbidity and mortality. Fractional flow reserve (FFR) was proposed in the 1990s to more accurately evaluate the functional severity of intermediate coronary stenosis, and it is currently the gold standard in cardiac catheterization laboratories where coronary pressure and flow are routinely obtained. The clinical measurement of FFR relies on a pressure wire for the recording of pressures; however, in computational fluid dynamics studies, an FFR is frequently predicted using a wire-absent model. We aim to investigate the influence of the physical presence of a 0.014-inch (≈0.36 mm) pressure wire in the calculation of virtual FFR. Ideal and patient-specific models were simulated with the absence and presence of a pressure wire. The computed FFR reduced from 0.96 to 0.93 after inserting a wire in a 3-mm non-stenosed (pipe) ideal model. In mild stenotic cases, the difference in FFR between the wire-absent and wire-included models was slight. The overestimation in severe case was large but is of less clinical significance because, in practice, this tight lesion does not require sophisticated measurement to be considered critical. However, an absence of the pressure wire in simulations could contribute to an over-evaluation for an intermediate coronary stenosis.

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