scholarly journals Functional assessment of coronary plaques using CT based hemodynamic simulations: current status, technical principles and clinical value

Imaging ◽  
2020 ◽  
Author(s):  
Melinda Boussoussou ◽  
Borbála Vattay ◽  
Bálint Szilveszter ◽  
Márton Kolossváry ◽  
Judit Simon ◽  
...  

Abstract:In recent years, coronary computed tomography angiography (CCTA) has emerged as an accurate and safe non-invasive imaging modality in terms of detecting and excluding coronary artery disease (CAD). In the latest European Society of Cardiology Guidelines CCTA received Class I recommendation for the evaluation of patients with stable chest pain with low to intermediate clinical likelihood of CAD. Despite its high negative predictive value, the diagnostic performance of CCTA is limited by the relatively low specificity, especially in patients with heavily calcified lesions. The discrepancy between the degree of stenosis and ischemia is well established based on both invasive and non-invasive tests. The rapid evolution of computational flow dynamics has allowed the simulation of CCTA derived fractional flow reserve (FFR-CT), which improves specificity by combining anatomic and functional information regarding coronary atherosclerosis. FFR-CT has been extensively validated against invasively measured FFR as the reference standard. Due to recent technological advancements FFR-CT values can also be calculated locally, without offsite processing. Wall shear stress (WSS) and axial plaque stress (APS) are additional key hemodynamic elements of atherosclerotic plaque characteristics, which can also be measured using CCTA images. Current evidence suggests that WSS and APS are important hemodynamic features of adverse coronary plaques. CCTA based hemodynamic calculations could therefore improve prognostication and the management of patients with stable CAD.

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Lei Xu ◽  
Zhonghua Sun ◽  
Zhanming Fan

Coronary CT angiography (CCTA) has become an important noninvasive imaging modality in the diagnosis of coronary artery disease (CAD). CCTA enables accurate evaluation of coronary artery stenosis. However, CCTA provides limited information on the physiological significance of stenotic lesions. A noninvasive “one-stop-shop” diagnostic test that can provide both anatomical significance and functional significance of stenotic lesions would be beneficial in the diagnosis and management of CAD. Recently, with the introduction of novel techniques, such as myocardial CT perfusion, CT-derived fractional flow reserve (FFRCT), and transluminal attenuation gradient (TAG), CCTA has emerged as a noninvasive method for the assessment of both anatomy of coronary lesions and its physiological consequences during a single study. This review provides an overview of the current status of new CT techniques for the physiologic assessments of CAD.


2016 ◽  
Vol 11 (1) ◽  
pp. 17
Author(s):  
Shah R Mohdnazri ◽  
◽  
◽  
◽  
Thomas R Keeble ◽  
...  

Fractional flow reserve (FFR) has been shown to improve outcomes when used to guide percutaneous coronary intervention (PCI). There have been two proposed cut-off points for FFR. The first was derived by comparing FFR against a series of non-invasive tests, with a value of ≤0.75 shown to predict a positive ischaemia test. It was then shown in the DEFER study that a vessel FFR value of ≥0.75 was associated with safe deferral of PCI. During the validation phase, a ‘grey zone’ for FFR values of between 0.76 and 0.80 was demonstrated, where a positive non-invasive test may still occur, but sensitivity and specificity were sub-optimal. Clinical judgement was therefore advised for values in this range. The FAME studies then moved the FFR cut-off point to ≤0.80, with a view to predicting outcomes. The ≤0.80 cut-off point has been adopted into clinical practice guidelines, whereas the lower value of ≤0.75 is no longer widely used. Here, the authors discuss the data underpinning these cut-off values and the practical implications for their use when using FFR guidance in PCI.


Author(s):  
Jian Liu ◽  
Yong Yu ◽  
Chenqi Zhu ◽  
Yu Zhang

The finite volume method (FVM)-based computational fluid dynamics (CFD) technology has been applied in the non-invasive diagnosis of coronary artery stenosis. Nonetheless, FVM is a time-consuming process. In addition to FVM, the lattice Boltzmann method (LBM) is used in fluid flow simulation. Unlike FVM solving the Navier–Stokes equations, LBM directly solves the simplified Boltzmann equation, thus saving computational time. In this study, 12 patients with left anterior descending (LAD) stenosis, diagnosed by CTA, are analysed using FVM and LBM. The velocities, pressures, and wall shear stress (WSS) predicted using FVM and LBM for each patient is compared. In particular, the ratio of the average and maximum speed at the stenotic part characterising the degree of stenosis is compared. Finally, the golden standard of LAD stenosis, invasive fractional flow reserve (FFR), is applied to justify the simulation results. Our results show that LBM and FVM are consistent in blood flow simulation. In the region with a high degree of stenosis, the local flow patterns in those two solvers are slightly different, resulting in minor differences in local WSS estimation and blood speed ratio estimation. Notably, these differences do not result in an inconsistent estimation. Comparison with invasive FFR shows that, in most cases, the non-invasive diagnosis is consistent with FFR measurements. However, in some cases, the non-invasive diagnosis either underestimates or overestimates the degree of stenosis. This deviation is caused by the difference between physiological and simulation conditions that remains the biggest challenge faced by all CFD-based non-invasive diagnostic methods.


2021 ◽  
Vol 138 ◽  
pp. 109633
Author(s):  
Andreas M. Fischer ◽  
Marly van Assen ◽  
U. Joseph Schoepf ◽  
Andrew J. Matuskowitz ◽  
Akos Varga-Szemes ◽  
...  

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
K T Madsen ◽  
K T Veien ◽  
B L Noergaard ◽  
P Larsen ◽  
L Deibjerg ◽  
...  

Abstract Introduction Coronary CT angiography (CTA) derived fractional flow reserve (FFRct) is increasingly used for guiding referral to invasive procedures in patients with stable chest pain. However, optimal interpretation of FFRct-analysis in terms of location and threshold of applied FFRct-values is unclear. Purpose To evaluate the clinical performance of various vessel-specific physiological FFRct derived measures of ischemia for prediction of standard of care guided coronary revascularization in patients with stable chest pain and coronary artery disease as determined by coronary CTA. Methods Retrospective study in patients with stable chest pain referred for coronary angiography based on coronary CTA. Standard acquired coronary CTA data sets were transmitted for core-laboratory analysis at HeartFlow. Any FFRct value in the major coronary arteries ≥1.8 mm in diameter, including side branches, were registered. Lesions were categorized as positive for ischemia using 6 different algorithms: Lowest in vessel FFRct-value (1) ≤0.75 or (2) ≤0.80; 2 cm distal-to-lesion FFRct-value (3) ≤0.75 or (4) ≤0.80; ΔFFRct (5) ≥0.06 or a combination of 2 and 5. The personnel responsible for downstream patient management had no information regarding FFRct test results. Results A total of 172 patients were included. Revascularization was performed in 62 (35%) patients. The diagnostic performance of different FFRct algorithms for predicting standard of care guided coronary revascularization is shown in the Table. Revascularization Predictions by FFRct N=172 Diagnostic performance FFRCT false negative FFRCT false positive Values given as (%) No. of revasc vessels No. of abnormal vessels FFRCT Algorithm Sens Spec PPV NPV Acc 1 2 3 1 2 3 Distal FFRCT ≤0.75 77 68 58 84 72 12 2 0 29 5 1 Distal FFRCT ≤0.80 92 43 48 90 61 5 0 0 40 20 3 Lesion-specific FFRCT ≤0.75 68 86 74 83 80 17 3 0 12 3 0 Lesion-specific FFRCT ≤0.80 82 78 68 89 80 10 2 0 21 3 1 ΔFFRCT ≥0.06 98 36 47 98 59 1 0 0 51 19 0 Combinationa 92 54 53 92 67 5 0 0 39 12 0 aDistal FFRCT ≤0.80 and ΔFFRCT ≥0.06. Sens = sensitivity; Spec = specificity; PPV = positive predictive value; NPV = negative predictive value; Acc = accuracy; FFRCT = fractional flow reserve derived from coronary CTA; ΔFFRCT = difference between FFRCT-value immediately proximal and distal to lesion; Revasc = revascularized. Conclusion The diagnostic performance of FFRct in terms of predicting standard of care guided coronary revascularization is dependent on the applied algorithm for interpretation of the FFRct-analysis.


Circulation ◽  
2015 ◽  
Vol 132 (suppl_3) ◽  
Author(s):  
Hiroyuki Arashi ◽  
Junichi Yamaguchi ◽  
Tonre Ri ◽  
Eiji Shibahashi ◽  
Ryosuke Itani ◽  
...  

Background: Instantaneous wave-free ratio (iFR) is a vasodilator free index calculated using trans-lesional pressure ratio during a specific period of diastole that is called “wave-free period”, and reported to have a good correlation with fractional flow reserve (FFR). In patients with severe aortic valve stenosis (AS), evaluation of intermediate coronary stenosis by FFR using vasodilators is thought to be a contraindication in some situations. Moreover, previous studies reported unique coronary flow pattern during diastolic phase in patients with AS. To date, there is no report claiming the correlation of iFR and FFR in this population. The purpose of the present study was to examine the clinical value of iFR in patients with AS. Method and Results: We examined consecutive 154 patients (with 214 stenosis) whose iFR and FFR were measured simultaneously. The mean age of AS patients (n=10, mean aortic valve area: 0.75 ± 0.42cm2) was higher than non-AS patients (n=144). Other patients’ characteristics are shown in Table 1. The mean iFR value in AS patients was significantly lower than that of non-AS patients, despite no significant difference was observed in the mean FFR value and % diameter stenosis (Table 2). iFR showed a good correlation with FFR in AS patients (Figure 1) and the best cut-off value of iFR in receiver operator curve analysis to predict FFR ≤ 0.8 was 0.73 in AS patients (AUC 0.84, sensitivity 0.8, specificity 0.86, p=0.016; Figure 2), whereas, 0.90 in non-AS patients. Conclusion: The present study demonstrated the good correlation between iFR and FFR in AS patients. Besides, the value below 0.73 of iFR was thought to be a predictor of myocardial ischemia in AS patients, which was lower than standard predictive range of ischemia in iFR. Vasodilator-free assessment by iFR may have potential benefits in evaluating intermediate coronary stenosis in patients with AS.


2018 ◽  
Vol 13 (6) ◽  
pp. 57 ◽  
Author(s):  
Keltoum Chahour ◽  
Rajae Aboulaich ◽  
Abderrahmane Habbal ◽  
Cherif Abdelkhirane ◽  
Nejib Zemzemi

The fractional flow reserve (FFR) provides an efficient quantitative assessment of the severity of a coronary lesion. Our aim is to address the problem of computing non-invasive virtual fractional flow reserve (VFFR). In this paper, we present a preliminary study of the main features of flow over a stenosed coronary arterial portion, in order to enumerate the different factors affecting the VFFR. We adopt a non-Newtonian flow model and we assume that the two-dimensional (2D) domain is rigid in a first place. In a second place, we consider a simplified weakly coupled FSI model in order to take into account the infinitesimal displacements of the upper wall. A 2D finite element solver was implemented using Freefem++. We computed the VFFR profiles with respect to different lesion parameters and compared the results given by the rigid wall model to those obtained for the elastic wall one.


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