Hemodynamic Significance Of Coronary Stenosis Research Articles

Simulation of coronary fractional flow reserve and whole-cycle flow based on optical coherence tomography in individual patients with coronary artery disease

Computer simulations of coronary fractional flow reserve (FFR) based on coronary imaging have emerged as an attractive alternative to invasive measurements. However, most methods are proprietary and employ non-physiological assumptions. Our aims were to develop and validate a physiologically realistic open-source simulation model for coronary flow, and to use this model to predict FFR based on intracoronary optical coherence tomography (OCT) data in individual patients. We included patients undergoing elective coronary angiography with angiographic borderline coronary stenosis. Invasive measurements of coronary hyperemic pressure and absolute flow and OCT imaging were performed. A computer model of coronary flow incorporating pulsatile flow and the effect of left ventricular contraction was developed and calibrated, and patient-specific flow simulation was performed. Forty-eight coronary arteries from 41 patients were included in the analysis. Average FFR was 0.79 ± 0.14, and 50% had FFR ≤ 0.80. Correlation between simulated and measured FFR was high (r = 0.83, p < 0.001). Average difference between simulated FFR and observed FFR in individual patients was − 0.009 ± 0.076. Overall diagnostic accuracy for simulated FFR ≤ 0.80 in predicting observed FFR ≤ 0.80 was 0.88 (0.75–0.95) with sensitivity 0.79 (0.58–0.93) and specificity 0.96 (0.79–1.00). The positive predictive value was 0.95 (0.75–1.00) and the negative predictive value was 0.82 (0.63–0.94). In conclusion, realistic simulations of whole-cycle coronary flow can be produced based on intracoronary OCT data with a new, computationally simple simulation model. Simulated FFR had moderate numerical agreement with observed FFR and a good diagnostic accuracy for predicting hemodynamic significance of coronary stenoses.

Quantitative Flow Ratio to Predict Non-Target-Vessel Events Before Planned Staged Percutaneous Coronary Intervention in Patients With Acute Coronary Syndrome.

The optimal time point of staged percutaneous coronary intervention (PCI) among patients with acute coronary syndrome (ACS) remains a matter of debate. Quantitative flow ratio (QFR) is a novel noninvasive method to assess the hemodynamic significance of coronary stenoses. We aimed to investigate whether QFR could refine the timing of staged PCI of non-target vessels (non-TVs) on top of clinical judgment for patients with ACS. For this cohort study, patients with ACS from Bern University Hospital, Switzerland, scheduled to undergo out-of-hospital non-TV staged PCI were eligible. The primary end point was the composite of non-TV myocardial infarction and urgent unplanned non-TV PCI before planned staged PCI. The association between lowest QFR per patient measured in the non-TV(from index angiogram) and the primary end point was assessed using multivariable adjusted Cox proportional hazards regressions with QFR included as linear or penalized spline (nonlinear) term. QFR was measured in 1093 of 1432 patients with ACS scheduled to undergo non-TV staged PCI. Median time to staged PCI was 28 days. The primary end point occurred in 5% of the patients. In multivariable analysis (1018 patients), there was no independent association between non-TV QFR and the primary end point (hazard ratio, 0.87 [95% CI, 0.69-1.05] per 0.1 increase; P=0.125; nonlinear P=0.648). In selected patients with ACS scheduled to undergo staged PCI at a median of 4 weeks after index PCI, QFR did not emerge as an independent predictor of non-TV events before planned staged PCI. Thus, this study does not provide conceptual evidence that QFR is helpful to refine the timing of staged PCI on top of clinical judgment. URL: https://www.clinicaltrials.gov; Unique identifier: NCT02241291.

Association between quantitative flow ratio and non-target-vessel-related events before planned staged percutaneous coronary intervention in patients with acute coronary syndrome

Abstract Introduction The optimal timepoint of non-target-vessel (non-TV) percutaneous coronary intervention (PCI) among patients with acute coronary syndrome (ACS) remains a matter of debate. Quantitative Flow Ratio (QFR) is a novel, non-invasive, vasodilator-free method to assess the hemodynamic significance of coronary stenoses. Purpose We aimed to investigate the association between non-TV QFR and non-TV-related events occurring prior to planned staged PCI (sPCI), to derive first conceptual knowledge, whether QFR could be useful to determine the optimal timepoint of sPCI. Methods Between 2009-2017, all ACS patients scheduled to undergo out-of-hospital sPCI within 6 months from index PCI at Bern University Hospital, Switzerland, were eligible for QFR measurement. The primary endpoint was non-TV myocardial infarction (MI) and urgent (unplanned) non-target-vessel PCI occurring before planned sPCI. QFR was measured using the index presentation angiogram in the non-TV planned for sPCI. The association between lowest QFR per patient (per 0.1) and the occurrence of the primary endpoint was assessed with a multivariable Cox proportional hazards regression including a penalized spline term for QFR and the variables age, sex, diabetes mellitus, renal failure, and diameter stenosis (DS%) (per 5%). Results Out of 8657 ACS patients, 1432 were scheduled to undergo sPCI, and 1093 patients (1262 vessels) were analyzed by QFR. At baseline, mean QFR was 0.73±0.17 and mean DS% 54.8±11.2%. sPCI was planned with median 28 days after the index PCI. In multivariable analysis (1018 patients, 51 events), there was no independent association between QFR and the primary endpoint (HR 0.87, 95% CI 0.69-1.05, p=0.125; QFR non-linear p=0.648). Conclusions In this cohort study of ACS patients scheduled to undergo out-of-hospital sPCI within median 28 days, QFR did not emerge as a predictor of non-TV events prior to planned sPCI. Thus, this study does not support the concept, that QFR would be helpful to determine the optimal timepoint of sPCI.Figure 1.Primary endpointTable 1.Cox model primary endpoint

Diagnostic performance of angiography-derived fractional flow reserve analysis based on bifurcation fractal law for assessing hemodynamic significance of coronary stenosis.

Blood flow into the side branch affects the calculation of coronary angiography-derived fractional flow reserve (FFR), called Angio-FFR. Neglecting or improperly compensating for the side branch flow may decrease the diagnostic accuracy of Angio-FFR. This study aims to evaluate the diagnostic accuracy of a novel Angio-FFR analysis that considers the side branch flow based on the bifurcation fractal law. A one-dimensional reduced-order model based on the vessel segment was used to perform Angio-FFR analysis. The main epicardial coronary artery was divided into several segments according to the bifurcation nodes. Side branch flow was quantified using the bifurcation fractal law to correct the blood flow in each vessel segment. In order to verify the diagnostic performance of our Angio-FFR analysis, two other computational methods were taken as control groups: (i) FFR_s: FFR calculated by delineating the coronary artery tree to consider side branch flow, (ii) FFR_n: FFR calculated by just delineating the main epicardial coronary artery and neglecting the side branch flow. The analysis of 159 vessels from 119 patients showed that our Anio-FFR calculation method had comparable diagnostic accuracy to FFR_s and provided significantly higher diagnostic accuracy than that of FFR_n. In addition, using invasive FFR as a reference, the Pearson correlation coefficients of Angio-FFR and FFRs were 0.92 and 0.91, respectively, while that of FFR_n was only 0.85. Our Angio-FFR analysis has demonstrated good diagnostic performance in assessing the hemodynamic significance of coronary stenosis by using the bifurcation fractal law to compensate for side branch flow. Bifurcation fractal law can be used to compensate for side branch flow during the Angio-FFR calculation of the main epicardial vessel. Compensating for side branch flow can improve the ability of Angio-FFR to diagnose stenosis functional severity. • The bifurcation fractal law could accurately estimate the blood flow from the proximal main vessel into the main branch, thus compensating for the side branch flow. • Angiography-derived FFR based on the bifurcation fractal law is feasible to evaluate the target diseased coronary artery without delineating the side branch.

Computational Analysis of Hemodynamic Indices Based on Personalized Identification of Aortic Pulse Wave Velocity by a Neural Network

Adequate personalized numerical simulation of hemodynamic indices in coronary arteries requires accurate identification of the key parameters. Elastic properties of coronary vessels produce a significant effect on the accuracy of simulations. Direct measurements of the elasticity of coronary vessels are not available in the general clinic. Pulse wave velocity (AoPWV) in the aorta correlates with aortic and coronary elasticity. In this work, we present a neural network approach for estimating AoPWV. Because of the limited number of clinical cases, we used a synthetic AoPWV database of virtual subjects to train the network. We use an additional set of AoPWV data collected from real patients to test the developed algorithm. The developed neural network predicts brachial–ankle AoPWV with a root-mean-square error (RMSE) of 1.3 m/s and a percentage error of 16%. We demonstrate the relevance of a new technique by comparing invasively measured fractional flow reserve (FFR) with simulated values using the patient data with constant (7.5 m/s) and predicted AoPWV. We conclude that patient-specific identification of AoPWV via the developed neural network improves the estimation of FFR from 4.4% to 3.8% on average, with a maximum difference of 2.8% in a particular case. Furthermore, we also numerically investigate the sensitivity of the most useful hemodynamic indices, including FFR, coronary flow reserve (CFR) and instantaneous wave-free ratio (iFR) to AoPWV using the patient-specific data. We observe a substantial variability of all considered indices for AoPWV below 10 m/s and weak variation of AoPWV above 15 m/s. We conclude that the hemodynamic significance of coronary stenosis is higher for the patients with AoPWV in the range from 10 to 15 m/s. The advantages of our approach are the use of a limited set of easily measured input parameters (age, stroke volume, heart rate, systolic, diastolic and mean arterial pressures) and the usage of a model-generated (synthetic) dataset to train and test machine learning methods for predicting hemodynamic indices. The application of our approach in clinical practice saves time, workforce and funds.

Morphometric Assessment for Functional Evaluation of Coronary Stenosis with Optical Coherence Tomography and the Optical Flow Ratio in a Vessel with Single Stenosis.

Objectives: The study aimed to evaluate the diagnostic performance of optical coherence tomography (OCT) in identifying functionally significant coronary stenosis in a vessel with single stenosis. Background: The OCT-based morphofunctional computational method for deriving the optical flow ratio (OFR) has diagnostic value, as it can identify the functional severity of coronary stenosis, but the ability of the OFR to aid the OCT in determining coronary stenosis hemodynamics in single-stenosis lesion remains unclear. Methods: 74 vessels with single stenosis were studied in 69 patients; all cases were performed through OCT and quantitative flow ratio (QFR), and OCT images were used to perform OFR. Results: Among vessels with single stenosis, OFR showed a good correlation with QFR (r = 0.86; p < 0.001). Taking QFR as the standard, the vessel-level diagnosis accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of OFR were 90% (95% CI: 81 to 96), 94% (95% CI: 77 to 99), 88% (95% CI: 74 to 96), 85% (95% CI: 68 to 94) and 95% (95% CI: 82 to 99), respectively. Among vessels with OFR/QFR concordance, both the minimum lumen area (MLA) and minimum lumen diameter (MLD) showed excellent diagnostic efficiency (MLA: area under the curve (AUC) = 0.92, 95% CI: 0.85 to 0.98, p < 0.001; MLD: AUC = 0.93, 95% CI: 0.86 to 0.98, p < 0.001) in determining the functional significance of coronary stenosis in a single stenosis lesion, and the best cutoff values were 1.55 mm2 and 1.40 mm. Conclusions: OFR has a good correlation with QFR. OCT-measured MLA and MLD have excellent diagnostic efficiency in identifying the hemodynamic significance of coronary stenosis in a vessel with single stenosis.

Diagnostic accuracy of coronary computed tomography angiography-derived fractional flow reserve (CT-FFR) in patients before liver transplantation using CT-FFR machine learning algorithm

ObjectivesLiver transplantation (LT) is associated with high stress on the cardiovascular system. Ruling out coronary artery disease (CAD) is an important part of evaluation for LT. The aim of our study was to assess whether CT-derived fractional flow reserve (CT-FFR) allows for differentiation of hemodynamically significant and non-significant coronary stenosis in patients evaluated for LT.MethodsIn total, 201 patients undergoing LT evaluation were included in the study. The patients received coronary computed tomography angiography (CCTA) to rule out CAD and invasive coronary angiography (ICA) to further evaluate coronary lesions found in CCTA if a significant (≥ 50 % on CCTA) stenosis was suspected. CT-FFR was computed from CCTA datasets using a machine learning–based algorithm and compared to ICA as a standard of reference. Coronary lesions with CT-FFR ≤ 0.80 were defined as hemodynamically significant.ResultsIn 127 of 201 patients (63%), an obstructive CAD was ruled out by CCTA. In the remaining 74 patients (37%), at least one significant stenosis was suspected in CCTA. Compared to ICA, sensitivity, specificity, PPV, and NPV of the CT-FFR measurements were 71% (49–92%), 90% (82–98%), 67% (45–88%), and 91% (84–99%), respectively. The diagnostic accuracy was 85% (85–86%). In 69% of cases (52 of 75 lesions), additional analysis by CT-FFR correctly excluded the hemodynamic significance of the stenosis.ConclusionsMachine learning–based CT-FFR seems to be a very promising noninvasive approach for exclusion of hemodynamic significant coronary stenoses in patients undergoing evaluation for LT and could help to reduce the rate of invasive coronary angiography in this high-risk population.Key Points• Machine learning–based computed tomography-derived fractional flow reserve (CT-FFR) seems to be a very promising noninvasive approach for exclusion of hemodynamic significance of coronary stenoses in patients undergoing evaluation for liver transplantation and could help to reduce the rate of invasive coronary angiography in this high-risk population.

Myocardial revascularization : Controversy over noninvasive and invasive detection of ischemia

With some exceptions, myocardial revascularization in patients with chronic coronary syndrome (CCS) is generally decided on the basis of the extent of myocardial ischemia. Current data indicate that apatient will benefit from revascularization if ischemia is present in more than 10% of the myocardium. Accordingly, all patients presenting with CCS should undergo anoninvasive ischemia test that can answer this question before diagnostic coronary angiography. In order to be able to make arecommendation for revascularization based on scientific data even in those patients who previously had no clear evidence of ischemia, e.g., because of discrepant findings, measurement of the hemodynamic significance of coronary stenoses with alumen diameter reduction ≥ 50% should be performed during coronary angiography. Adecision to revascularize based on hemodynamic significance was shown to be beneficial to patients in several studies.

Updated Meta-Analysis Comparing FFR-Guided and Angiographic-Guided Intervention in Patients with Multivessel Coronary Artery Disease

A new method to guide Percutaneous Coronary Interventions (PCI) and Coronary Artery Bypass Graft (CABG) interventions are by FFR, which is a measurement of the hemodynamic significance of coronary stenosis. We conducted an updated meta-analysis of all randomized controlled trials from inception to 5 December 2021 to compare studies that included patients who underwent FFR-guided PCI or CABG. The statistical analysis was performed using a random effect model to Calculate Risk Ratios (RR) and Mean Difference (MD) with 95% Confidence Intervals (CI). Five RCTs were included with a total of 2,288 patients and a median weighted follow-up period of 16.6 months. In this meta-analysis with a small sample size, there was no difference between FFR-guided and angiographicguided interventions for the rates of MACE and all-cause mortality. Moreover, the analysis showed that FFR-guided was associated with insignificantly decreased rates of MI (RR 0.77, 95% CI 0.51-1.16, p=0.21, I2=18%) and the number of revascularizations (RR 0.82, 95% CI 0.64-1.06, p=0.12, I2=0%). Finally, the average number of stents used per patient significantly favored the FFR-guided group (MD -0.16, 95% CI -0.24 to -0.07, p=0.0003, I2=93%). In conclusion, although FFR-guided did not have any benefit in decreasing MACE or allcause mortality, it was associated with improved outcomes of MI, the number of revascularizations, and the average number of stents.

SmartFFR, a New Functional Index of Coronary Stenosis: Comparison With Invasive FFR Data.

Aims: In this study, we evaluate the efficacy of SmartFFR, a new functional index of coronary stenosis severity compared with gold standard invasive measurement of fractional flow reserve (FFR). We also assess the influence of the type of simulation employed on smartFFR (i.e. Fluid Structure Interaction vs. rigid wall assumption).Methods and Results: In a dataset of 167 patients undergoing either computed tomography coronary angiography (CTCA) and invasive coronary angiography or only invasive coronary angiography (ICA), as well as invasive FFR measurement, SmartFFR was computed after the 3D reconstruction of the vessels of interest and the subsequent blood flow simulations. 202 vessels were analyzed with a mean total computational time of seven minutes. SmartFFR was used to process all models reconstructed by either method. The mean FFR value of the examined dataset was 0.846 ± 0.089 with 95% CI for the mean of 0.833–0.858, whereas the mean SmartFFR value was 0.853 ± 0.095 with 95% CI for the mean of 0.84–0.866. SmartFFR was significantly correlated with invasive FFR values (RCCTA = 0.86, pCCTA < 0.0001, RICA = 0.84, pICA < 0.0001, Roverall = 0.833, poverall < 0.0001), showing good agreement as depicted by the Bland-Altman method of analysis. The optimal SmartFFR threshold to diagnose ischemia was ≤0.83 for the overall dataset, ≤0.83 for the CTCA-derived dataset and ≤0.81 for the ICA-derived dataset, as defined by a ROC analysis (AUCoverall = 0.956, p < 0.001, AUCICA = 0.975, p < 0.001, AUCCCTA = 0.952, p < 0.001).Conclusion: SmartFFR is a fast and accurate on-site index of hemodynamic significance of coronary stenosis both at single coronary segment and at two or more branches level simultaneously, which can be applied to all CTCA or ICA sequences of acceptable quality.

Quantitative Flow Ratio to Predict Nontarget Vessel-Related Events at 5 Years in Patients With ST-Segment-Elevation Myocardial Infarction Undergoing Angiography-Guided Revascularization.

BackgroundIn ST‐segment–elevation myocardial infarction, angiography‐based complete revascularization is superior to culprit‐lesion‐only percutaneous coronary intervention. Quantitative flow ratio (QFR) is a novel, noninvasive, vasodilator‐free method used to assess the hemodynamic significance of coronary stenoses. We aimed to investigate the incremental value of QFR over angiography in nonculprit lesions in patients with ST‐segment–elevation myocardial infarction undergoing angiography‐guided complete revascularization.Methods and ResultsThis was a retrospective post hoc QFR analysis of untreated nontarget vessels (any degree of diameter stenosis [DS]) from the randomized multicenter COMFORTABLE AMI (Comparison of Biolimus Eluted From an Erodible Stent Coating With Bare Metal Stents in Acute ST‐Elevation Myocardial Infarction) trial by assessors blinded for clinical outcomes. The primary end point was cardiac death, spontaneous nontarget vessel myocardial infarction, and clinically indicated nontarget vessel revascularization (ie, ≥70% DS by 2‐dimensional quantitative coronary angiography or ≥50% DS and ischemia) at 5 years. Of 1161 patients with ST‐segment–elevation myocardial infarction, 946 vessels in 617 patients were analyzable by QFR. At 5 years, the rate of the primary end point was significantly higher in patients with QFR ≤0.80 (n=35 patients, n=36 vessels) versus QFR >0.80 (n=582 patients, n=910 vessels) (62.9% versus 12.5%, respectively; hazard ratio [HR], 7.33 [95% CI, 4.54–11.83], P<0.001), driven by higher rates of nontarget vessel myocardial infarction (12.8% versus 3.1%, respectively; HR, 4.38 [95% CI, 1.47–13.02], P=0.008) and nontarget vessel revascularization (58.6% versus 7.7%, respectively; HR, 10.99 [95% CI, 6.39–18.91], P<0.001) with no significant differences for cardiac death. Multivariable analysis identified QFR ≤0.80 but not ≥50% DS by 3‐dimensional quantitative coronary angiography as an independent predictor of the primary end point. Results were consistent, including only >30% DS by 3‐dimensional quantitative coronary angiography.ConclusionsOur study suggests incremental value of QFR over angiography‐guided percutaneous coronary intervention for nonculprit lesions among patients with ST‐segment–elevation myocardial infarction undergoing primary percutaneous coronary intervention.

Accuracy of Intravascular Ultrasound-Based Fractional Flow Reserve in Identifying Hemodynamic Significance of Coronary Stenosis.

Ultrasonic flow ratio (UFR) is a novel method for fast computation of fractional flow reserve (FFR) from intravascular ultrasound images. The objective of this study is to evaluate the diagnostic performance of UFR using wire-based FFR as the reference. Post hoc computation of UFR was performed in consecutive patients with both intravascular ultrasound and FFR measurement in a core lab while the analysts were blinded to FFR. A total of 167 paired comparisons between UFR and FFR from 94 patients were obtained. Median FFR was 0.80 (interquartile range, 0.68-0.89) and 50.3% had a FFR≤0.80. Median UFR was 0.81 (interquartile range, 0.69-0.91), and UFR showed strong correlation with FFR (r=0.87; P<0.001). The area under the curve was higher for UFR than intravascular ultrasound-derived minimal lumen area (0.97 versus 0.89, P<0.001). The diagnostic accuracy, sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for UFR to identify FFR≤0.80 was 92% (95% CI, 87-96), 91% (95% CI, 82-96), 96% (95% CI, 90-99), 96% (95% CI, 89-99), 91% (95% CI, 93-96), 25.0 (95% CI, 8.2-76.2), and 0.10 (95% CI, 0.05-0.20), respectively. The agreement between UFR and FFR was independent of lesion locations (P=0.48), prior myocardial infarction (P=0.29), and imaging catheters (P=0.22). Intraobserver and interobserver variability of UFR analysis was 0.00±0.03 and 0.01±0.03, respectively. Median UFR analysis time was 102 (interquartile range, 87-122) seconds. UFR had a strong correlation and good agreement with FFR. The fast computational time and excellent analysis reproducibility of UFR bears the potential of a wider adoption of integration of coronary imaging and physiology in the catheterization laboratory.

Quantitative flow ratio to predict non-target-vessel-related events at 5 years in STEMI patients undergoing angiography-guided revascularization

Abstract Background In patients with ST-segment-elevation myocardial infarction (STEMI), angiography-based complete revascularization is associated with superior outcomes compared with culprit-lesion-only percutaneous coronary intervention (PCI). Quantitative Flow Ratio (QFR) is a novel, non-invasive, vasodilator-free method to assess the hemodynamic significance of coronary stenoses. Purpose To investigate the incremental value of QFR over angiography alone in the assessment of non-culprit lesions (NCL) in STEMI patients undergoing primary PCI. Methods In the randomized, multicenter COMFORTABLE AMI trial, STEMI patients underwent angiography-guided complete revascularization. QFR was determined in untreated non-target vessels by assessors blinded for clinical outcomes. Results Out of 1161 STEMI patients, 946 vessels in 617 patients could be analyzed by QFR. At 5-year follow-up, the rate of the primary endpoint cardiac death, non-target vessel myocardial infarction (non-TV-MI) and clinically indicated, non-target vessel revascularization (non-TVR) was significantly higher in patients with QFR ≤0.80 compared with QFR &amp;gt;0.80 (62.9% vs. 12.7%, HR 7.20, 95% CI 4.46–11.62, p&amp;lt;0.001), driven by higher rates of non-TV-MI (15.4% vs. 3.6%, HR 4.59, 95% CI 1.72–12.23, p=0.002) and non-TVR (58.6% vs. 7.7%, HR 10.99, 95% CI 6.39–18.91, p&amp;lt;0.001). No significant differences for cardiac death were observed. Multivariate analysis identified QFR ≤0.80, MI SYNTAX score and left ventricular function as independent predictors of the primary endpoint. QFR ≤0.80 showed an accuracy of 86.1%, sensitivity of 23.2%, specificity of 97.5%, positive predictive value of 62.9% and negative predictive value of 87.5% for the prediction of the primary endpoint. Conclusions Our study results suggest incremental value of QFR over angiography-guided PCI for NCL among STEMI patients undergoing primary PCI. Kaplan-Meier curves of primary endpoint Funding Acknowledgement Type of funding source: None

Pressure-flow curve derived from coronary CT angiography for detection of significant hemodynamic stenosis.

Coronary CT angiography (cCTA) has been used to non-invasively assess both the anatomical and hemodynamic significance of coronary stenosis. The current study investigated a new CFD-based method of evaluating pressure-flow curves across a stenosis to further enhance the diagnostic value of cCTA imaging. Fifty-eight patients who underwent both cCTA imaging and invasive coronary angiography (ICA) with fractional flow reserve (FFR) within 2weeks were enrolled. The pressure-flow curve-derived parameters, viscous friction (VF) and expansion loss (EL), were compared with conventional cCTA parameters including percent area stenosis (AS) and minimum lumen area (MLA) by receiver operating characteristic (ROC) curve analysis. FFR ≤ 0.80 was used to indicate ischemia-causing stenosis. Correlations between FFR and other measurements were calculated by Spearman's rank correlation coefficient (rho). Sixty-eight stenoses from 58 patients were analyzed. VF, EL, and AS were significantly larger in the group of FFR ≤ 0.8 while smaller MLA values were observed. The ROC-AUC of VF (0.91, 95% CI 0.81-0.96) was better than that of AS (change in AUC (ΔAUC) 0.27, p < 0.05) and MLA (ΔAUC 0.17, p < 0.05), and ROC-AUC of EL (0.90, 95%CI 0.80-0.96) was also better than that of AS (ΔAUC 0.26, p < 0.05) and MLA (ΔAUC 0.16, p < 0.05). FFR values correlated well with VF (rho = - 0.74 (95% CI - 0.83 to - 0.61, p < 0.0001) and EL (rho = - 0.74 (95% CI - 0.83 to - 0.61, p < 0.0001). Pressure-flow curve-derived parameters enhance the diagnostic value of cCTA examination. • Pressure-flow curve derived from cCTA can assess coronary lesion severity. • VF and EL are superior to cCTA alone for indicating ischemic lesions. • Pressure-flow curve derived from cCTA may assist in clinical decision-making.

Diagnostic performance of perivascular fat attenuation index to predict hemodynamic significance of coronary stenosis: a preliminary coronary computed tomography angiography study.

This study aimed to investigate the association between perivascular fat attenuation index (FAI) and hemodynamic significance of coronary lesions. Patients with stable angina who underwent coronary computed tomography (CT) angiography and invasive fractional flow reserve (FFR) measurement within 2weeks were retrospectively included. Lesion-based perivascular FAI, high-risk plaque features, total plaque volume (TPV), machine learning-based FFRCT, and other parameters were recorded. Lesions with invasive FFR ≤ 0.8 were considered functionally significant. This study included 167 patients with 219 lesions. Diameter stenosis (DS), lesion length, TPV, and perivascular FAI were significantly larger or longer in the group of hemodynamically significant lesions (FFR ≤ 0.8). In addition, smaller FFRCT value was associated with functionally significant lesions (0.720 ± 0.11 vs 0.846 ± 0.10, p < 0.001). No significant difference was found between the hemodynamically significant and insignificant subgroups with respect to CT-derived high-risk plaque features. According to multivariate analysis, DS, TPV, and perivascular FAI were significant predictors of lesion-specific ischemia. When integrating DS, TPV, and perivascular FAI, the area under the curve (AUC) of this combined method was 0.821, which was similar to that of FFRCT (AUC, 0.821 vs 0.850; p = 0.426). The diagnostic accuracy of FFRCT was higher than that of the combined approach, but the difference was statistically insignificant (79.0% vs 74.0%, p = 0.093). Perivascular FAI was significantly higher for flow-limiting lesions than for non-flow-limiting lesions. The combined use of FAI, TPV, and DS could predict ischemic coronary stenosis with high diagnostic accuracy. • Perivascular FAI was significantly higher for flow-limiting lesions than for non-flow-limiting lesions. • Combined use of FAI, plaque volume, and DS provided diagnostic performance comparable to that of machine learning-based FFR CTfor predicting ischemic coronary stenosis. • No significant difference was found between the hemodynamically significant and insignificant subgroups with respect to CT-derived high-risk plaque features.

Cardiac CT: why, when, and how : Update 2019.

The aim of this study was to review established and emerging techniques of cardiac computed tomography (CT) and their clinical applications with aspecial emphasis on new techniques, recent trials, and guidelines. Cardiac CT has made great strides in recent years to become an ever more robust and safe imaging technique. The improvements in spatial and temporal resolution are equally important as the substantial reduction in radiation exposure, which has been achieved through prospective ECG-triggering, low tube voltage scanning, tube current modulation, and iterative reconstruction techniques. CT-derived fractional flow reserve and CT myocardial perfusion imaging are novel, investigational techniques to assess the hemodynamic significance of coronary stenosis. In asymptomatic patients at risk for coronary artery disease, CT coronary artery calcium scoring is useful to assess cardiovascular risk and guide the intensity of risk factor modification. Coronary CT angiography is an excellent noninvasive test to rule out obstructive coronary artery disease in patients with stable chest pain. In acute chest pain with normal ECG and normal cardiac enzymes, cardiac CT can safely rule out acute coronary syndrome although its benefit and role in this indication remains controversial. Cardiac CT is the established standard for planning transcatheter aortic valve implantation and-increasingly-minimally invasive mitral valve procedures. Our review makes practical recommendations on when and how to perform cardiac CT and provides templates for structured reporting of cardiac CT examinations.

Instantaneous wave-free ratio (iFR®) to determine hemodynamically significant coronary stenosis: A comprehensive review.

Coronary angiography is considered to be the gold standard in the morphological evaluation of coronary artery stenosis. The morphological assessment of the severity of a coronary lesion is very subjective. Thus, the invasive fractional flow reserve (FFR) measurement represents the current standard for estimation of the hemodynamic significance of coronary artery stenosis. The FFR-guided revascularization strategy was initially classified as a Class-IA-recommendation in the 2014 European Society of Cardiology/European Association for Cardio-Thoracic Surgery guidelines on myocardial revascularization. Both the Deferral vs Performance of Percutaneous Coronary Intervention of Functionally Non-Significant Coronary Stenosis and Flow Reserve vs Angiography for Multivessel Evaluation studies showed no treatment advantage for hemodynamically insignificant stenoses. With the help of FFR (and targeted interventions), clinical results could be improved; however, the use in clinical practice is still limited due to the need of adenosine administration and a significant prolongation of the length of the procedure. Instantaneous wave-free ratio (iFR®) is a new innovative approach for the determination of the hemodynamic significance of coronary stenosis, which can be obtained at rest without the use of vasodilators. Regarding the periprocedural complications as well as prognosis, iFR® showed non-inferiority to FFR in the SWEDEHEART and DEFINE-FLAIR trials. Furthermore, iFR®, enhanced by iFR®-pullback, provides the possibility to display the iFR®-change over the course of the vessel to create a hemodynamic map.

Numerical analysis of the impact of flow rate, heart rate, vessel geometry, and degree of stenosis on coronary hemodynamic indices

BackgroundThe stenosis of the coronary arteries is usually caused by atherosclerosis. Hemodynamic significance of patient-specific coronary stenoses and the risk of its progression may be assessed by comparing the hemodynamic effects induced by flow disorders. The present study shows how stenosis degree and variable flow conditions in coronary artery affect the oscillating shear index, residence time index, pressure drop coefficient and fractional flow reserve. We assume that changes in the hemodynamic indices in relation to variable flow conditions and geometries evaluated using the computational fluid dynamics may be an additional factor for a non-invasive assessment of the coronary stenosis detected on multi-slice computed tomography.MethodsThe local-parametrised models of basic shapes of the vessels, such as straight section, bend, and bifurcation as well as the global-patient-specific models of left coronary artery were used for numerical simulation of flow in virtually reconstructed stenotic vessels. Calculations were carried out for vessels both without stenosis, and vessels of 10 to 95% stenosis. The flow rate varied within the range of 20 to 1000 ml/min, and heart rate frequency within the range of 30 to 210 cycles/min.The computational fluid dynamics based on the finite elements method verified by the experimental measurements of the velocity profiles was used to analyse blood flow in the coronary arteries.ResultsThe results confirm our preliminary assumptions. There is significant variation in the coronary hemodynamic indices value caused by disturbed flow through stenosis in relation to variable flow conditions and geometry of vessels.ConclusionVariations of selected hemodynamic indexes induced by change of flow rate, heart rate and vessel geometry, obtained during a non-invasive study, may assist in evaluating the risk of stenosis progression and in carrying out the assessment of the hemodynamic significance of coronary stenosis. However, for a more accurate assessment of the variability of indices and coronary stenosis severity both local (near the narrowing) and global (in side branches) studies should be used.

Numerical analysis of the pressure drop across highly-eccentric coronary stenoses: application to the calculation of the fractional flow reserve

BackgroundFractional flow reverse (FFR) is the gold standard assessment of the hemodynamic significance of coronary stenoses. However, it requires the catheterization of the coronary artery to determine the pressure waveforms proximal and distal to the stenosis. On the contrary, computational fluid dynamics enables the calculation of the FFR value from relatively non-invasive computed tomography angiography (CTA).MethodsWe analyze the flow across idealized highly-eccentric coronary stenoses by solving the Navier–Stokes equations. We examine the influence of several aspects (approximations) of the simulation method on the calculation of the FFR value. We study the effects on the FFR value of errors made in the segmentation of clinical images. For this purpose, we compare the FFR value for the nominal geometry with that calculated for other shapes that slightly deviate from that geometry. This analysis is conducted for a range of stenosis severities and different inlet velocity and pressure waveforms.Results and conclusionsThe errors made in assuming a uniform velocity profile in front of the stenosis, as well as those due to the Newtonian and laminar approximations, are negligible for stenosis severities leading to FFR values around the threshold 0.8. The limited resolution of the stenosis geometry reconstruction is the major source of error when predicting the FFR value. Both systematic errors in the contour detection of just 1-pixel size in the CTA images and a low-quality representation of the stenosis surface (coarse faceted geometry) may yield wrong outcomes of the FFR assessment for an important set of eccentric stenoses. On the contrary, the spatial resolution of images acquired with optical coherence tomography may be sufficient to ensure accurate predictions for the FFR value.

Correlation between Angiographic and Physiologic Evaluation of Coronary Artery Narrowings in Patients With Aortic Valve Stenosis

We aimed to assess the correlation between angiographic and physiologic evaluation of coronary lesions in aortic stenosis (AS) patients presenting with intermediate coronary stenoses at the angiography. From 2002 to 2010, we included 163 patients from 2 centers with both AS and coronary artery disease (CAD), matched by age and gender with 163 contemporary patients with CAD alone. With both quantitative coronary angiography and fractional flow reserve (FFR), we assessed 259 coronary stenoses in the AS+ CAD group, and 256 in the CAD alone group. A significant correlation was found between diameter stenosis (DS) and FFR in both groups, although this was significantly stronger in the AS+ CAD than in the CAD alone group (R=-0.63 vs-0.44, p <0.01). Likewise, the correlation between minimum lumen diameter and FFR was stronger in the AS+ CAD than in the CAD alone group (R=-0.54 vs-0.41, p= 0.05). Receiver operator characteristic curves analysis showed that DS was a better predictor of hemodynamically significant coronary stenoses (FFR ≤0.8) in the AS+ CAD rather than in the CAD alone group (area under the curve= 0.83 vs 0.67, p <0.01). With 50% DS cut-off value, the sensitivity, specificity, and accuracy was 77%, 66%, and 70% in the AS+ CAD group versus 59%, 63%, and 61% in the CAD alone group. In both groups, the diagnostic accuracy of DS in predicting FFR was higher in the right and circumflex coronary artery compared with the left anterior descending artery (LAD), although this was only statistically significant in the AS+ CAD group (area under the curve 0.88 in the right and circumflex coronary artery vs 0.76 in LAD, p= 0.03). In conclusion, the correlation between the angiographic and hemodynamic significance of coronary stenoses is modest in AS patients. The assessment of CAD severity solely based on angiography poorly predicts the hemodynamic significance of the coronary stenosis especially when these are located in the LAD.