3D Quantitative Coronary Angiography Research Articles

Association Between Automated 3D Measurement of Coronary Luminal Narrowing and Risk of Future Myocardial Infarction.

This study focuses on identifying anatomical markers with predictive capacity for long-term myocardial infarction (MI) in focal coronary artery disease (CAD). Eighty future culprit lesions (FCL) and 108 non-culprit lesions (NCL) from 80 patients underwent 3D quantitative coronary angiography. The minimum lumen area (MLA), minimum lumen ratio (MLR), and vessel fractional flow reserve (vFFR) were evaluated. MLR was defined as the ratio between MLA and the cross-sectional area at the proximal lesion edge, with lower values indicating more abrupt luminal narrowing. Significant differences were observed between FCL and NCL in MLR (0.41 vs. 0.53, p < 0.001). MLR correlated inversely with translesional vFFR (r = - 0.26, p = 0.0004) and was the strongest predictor of MI at 5years (AUC = 0.75). Lesions with MLR < 0.40 had a fourfold increased MI incidence at 5years. MLR is a robust predictor of future adverse coronary events.

Effect of alirocumab on quantitative flow ratio and diameter stenosis in non-infarct related arteries from patients with acute myocardial infarction: a PACMAN-AMI randomized clinical trial substudy

Abstract Introduction Treating hypercholesterolemia with proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors on top of statins leads to plaque regression and stabilization. The effects of PCSK9 inhibitors on coronary physiology and angiographic diameter stenosis (DS%) are unknown. Quantitative Flow Ratio (QFR) is a novel method to assess coronary hemodynamics. Purpose We aimed to investigate the effects of the PCSK9 inhibitor alirocumab on QFR and 3D-Quantitative Coronary Angiography (3D-QCA) DS% in non-infarct-related arteries (non-IRA) among acute myocardial infarction (AMI) patients. Methods This was a pre-specified substudy of the PACMAN trial, a randomized, double-blind, placebo-controlled trial comparing alirocumab vs. placebo on top of high-intensity rosuvastatin among AMI patients. QFR and 3D-QCA were assessed at baseline and 1-year follow-up in any non-infarct related artery (non-IRA) with ≥2.0mm diameter and &amp;gt;25% 3D-QCA DS%. The pre-specified primary endpoint was the number of patients with mean QFR increase from baseline to follow-up, and the secondary endpoint the change in 3D-QCA DS%. Results Of 300 enrolled patients, 265 had serial follow-up, of which 193 underwent serial QFR/3D-QCA analysis in 282 non-IRA. Baseline mean QFR was 0.96[IQR 0.91-0.98] and mean DS% 36.96±7.88% in the alirocumab group vs. 0.96[IQR 0.91-0.99] (p=0.593) and 36.63±8.46% (p=0.742) in the placebo group. At 1-year, QFR increased in 50/94 (53.2%) patients with alirocumab vs. 40/99 (40.4%) with placebo (Δ12.8%; OR=1.7, 95%CI 0.9-3.0; p=0.076). When excluding non-IRA with QFR &amp;gt;0.95, QFR increased in 37/57 (64.9%) patients with alirocumab vs. 22/50 (44.0%) with placebo (Δ20.9%; OR=2.4, 95%CI 1.1-5.2; p=0.031). DS% decreased by -1.03±7.28% with alirocumab and increased by +1.70±8.27% with placebo (Δ-2.54%, 95%CI -4.51 to -0.57; p=0.012). Conclusions Treatment of AMI patients with alirocumab vs. placebo for 1 year resulted in a significant regression in angiographic DS%. While no overall improvement of coronary hemodynamics was observed with alirocumab as compared to placebo, potential benefits were found in alirocumab treated patients with baseline QFR ≤0.95.Figure 1.Flowchart and primary endpointFigure 2.Secondary endpoint

Inter-corelab agreement of angiography-derived wall shear stress distribution

Abstract Aims Wall shear stress (WSS) estimated in models reconstructed from intravascular imaging and 3D-quantitative coronary angiography (QCA) data provides important prognostic information and enables the identification of high-risk lesions. However, these analyses are time-consuming and require expertise limiting WSS applications and adoption in clinical practice. Recently, a novel software has been developed for real-time computation of WSS and multidirectional WSS distribution. The aim of this study is to examine its inter-corelab reproducibility. Methods and results Sixty lesions (20 in coronary bifurcations) with a borderline negative fractional flow reserve were selected and processed using the CAAS Workstation WSS prototype (version 6.0 PIE MEDICAL) to estimate WSS and multi-directional WSS. Analysis was performed by two Core laboratories; the estimations of the two corelabs for the WSS in 3 mm segments across each reconstructed vessel were extracted and compared. To examine the concordance between inter-observer analysis of clinically relevant values, the scatterplot was divided into 4 quadrants with AS 61.3% and maximum WSS 8.24 Pa based on the previous publications and Cohen’s Kappa value was presented using these cut-off values. In total 700 segments (256 located in bifurcated vessels) were included in the present analysis. Average analysis time on the software was 219±45s in straight model and 291±61s in bifurcation model. A high intraclass correlation was noted for all the WSS metrics for the estimations of the two core labs irrespective of the presence (range: 0.90 – 0.92) or absence (range: 0.89 - 0.90) of a coronary bifurcation, while the ICC was good-moderate for the multidirectional WSS (range: 0.72-0.86). In addition, the bias between the WSS estimations was low and the limits of agreement were narrow in Bland-Altman analyses (Figure 1). When using the cut-off value of maximum WSS and % AS, a substantial agreement was noted between the two estimations of the two core labs; κ=0.77 for identifying maximum WSS &amp;gt;8.24Pa and κ=0.71 for identifying AS &amp;gt;61.3% (Figure 2). Conclusion The CAAS workstation enables reproducible 3D-QCA reconstruction and computation of WSS metrics. Further research is needed to explore its efficacy in predicting cardiovascular events.Figure 1Figure 2

Angiography and optical coherence tomography derived shear stress: are they equivalent in my opinion?

Advances in image reconstruction using either single or multimodality imaging data provide increasingly accurate three-dimensional (3D) patient's arterial models for shear stress evaluation using computational fluid dynamics (CFD). We aim to evaluate the impacts on endothelial shear stress (ESS) derived from a simple image reconstruction using 3D-quantitative coronary angiography (3D-QCA) versus a multimodality reconstruction method using optical coherence tomography (OCT) in patients' vessels treated with bioresorbable scaffolds. Seven vessels at baseline and five-year follow-up of seven patients from a previous CFD investigation were retrospectively selected for a head-to-head comparison of angiography-derived versus OCT-derived ESS. 3D-QCA significantly underestimated the minimum stent area [MSA] (-2.38mm2) and the stent length (-1.46mm) compared to OCT-fusion method reconstructions. After carefully co-registering the region of interest for all cases with a sophisticated statistical method, the difference in MSA measurements as well as the inability of angiography to visualise the strut footprint in the lumen surface have translated to higher angiography-derived ESS than OCT-derived ESS (1.76Pa or 1.52 times for the overlapping segment). The difference in ESS widened with a more restricted region of interest (1.97Pa or 1.63 times within the scaffold segment). Angiography and OCT offer two distinctive methods of ESS calculation. Angiography-derived ESS tends to overestimate the ESS compared to OCT-derived ESS. Further investigations into ESS analysis resolution play a vital role in adopting OCT-derived ESS.

3D quantitative coronary angiography based vessel FFR: clinical evidence and future perspectives

3D quantitative coronary angiography based vessel FFR: clinical evidence and future perspectives

Fractional flow reserve or 3D-quantitative-coronary-angiography based vessel-FFR guided revascularization. Rationale and study design of the prospective randomized fast III trial

Physiological assessment of intermediate coronary lesions to guide coronary revascularization is currently recommended by international guidelines. Vessel fractional flow reserve (vFFR) has emerged as a new approach to derive fractional flow reserve (FFR) from 3D-quantitative coronary angiography (3D-QCA) without the need for hyperemic agents or pressure wires. The FAST III is an investigator-initiated, open label, multicenter randomized trial comparing vFFR guided versus FFR guided coronary revascularization in approximately 2228 patients with intermediate coronary lesions (defined as 30%-80% stenosis by visual assessment or QCA). Intermediate lesions are physiologically assessed using on-line vFFR or FFR and treated if vFFR or FFR ≤0.80. The primary end point is a composite of all-cause death, any myocardial infarction, or any revascularization at 1-year post-randomization. Secondary end points include the individual components of the primary end point and cost-effectiveness will be investigated. FAST III is the first randomized trial to explore whether a vFFR guided revascularization strategy is non-inferior to an FFR guided strategy in terms of clinical outcomes at 1-year follow-up in patients with intermediate coronary artery lesions.

P73 ANGIOGRAPHY–DERIVED INDEX OF MICROVASCULAR RESISTANCE (IMR–ANGIO) IN TAKOTSUBO SYNDROME

Abstract Introduction Coronary microvascular dysfunction (CMD) has been proposed as a key driver in the etiopathogenesis of Takotsubo syndrome (TTS), likely related to an “adrenergic storm” upon a susceptible microvascular circulation. The aim of our manuscript was to assess and quantify CMD in patients with TTS through non–invasive angio–derived index of microcirculation (IMRangio) and evaluate its correlation with clinical and instrumental presentation. Methods 41 consecutive TTS patients were retrospectively analyzed. Three different formulas for compute Non–Hyperemic IMRangio (NH–IMRangio) derived by 3D–Quantitative Coronary Angiography (3D–QCA) and Quantitative Flow Reserve (QFR) analysis were used according to each fluidodynamic mathematical expression as reported by respective authors. CMD was defined as an IMRangio ≥ 25. The correlation between NH–IMRangio and clinical presentation and the comparation between the three formulas were provided. Results Median age was 76 years, 85.7% were women and mean left ventricular ejection fraction (LVEF) at first echocardiogram was 41.2%. NH–IMRangio was higher in Left Anterior Descending artery (LAD) than Circumflex artery (CX) and Right Coronary artery (RCA) with either NH–IMRangio 1 (52.7 vs 35.3 vs 41.4), NH–IMRangio 2 (47.2 vs 31.8 vs 37.3) or NH–IMRangio 3 (52.7 vs 36.1 vs 41.8). All patients presented CMD with NH–IMR angio ≥ 25 in at least one territory with each formula. NH–IMRangio in LAD territory was significantly higher in patients presenting with LVEF impairment (≤40%) than in those with preserved ventricular global function (NH–IMRangio LAD 1: 59.3 vs 46.3, p. value=0.030; NH–IMRangio LAD 2: 52.9 vs 41.4, p–value=0.037; NH–IMRangio LAD 3: 59.2 vs 46.3, p–value=0–035). Association between NH–IMRangio computed in LAD and LVEF showed a moderate correlation (NH–IMRangio 1: r = –0,3485, Rho = 0,1214, p = 0,0256; NH–IMRangio 2: r = –0,3513; Rho = 0,1234, p = 0,0256; NH–IMRangio 3: r = –0,3326, Rho = 0,1106, p = 0,0336). Finally, Bland–Altman plot analysis showed good agreement between NH–IMRangio 1 and 3, while NH–IMRangio 2 showed a consistent bias of –5 units against both NH–IMRangio 1 and NH–IMRangio 2 with increasing difference at higher absolute values. Conclusion CMD, assessed with NH–IMRangio, is a common finding in TTS and it is inversely correlate with LVEF dysfunction. The available formulas for NH–IMRangio computation have a substantial superimposable diagnostic performance in assessing CMD.

An automated software for real-time quantification of wall shear stress distribution in quantitative coronary angiography data

BackgroundWall shear stress (WSS) estimated in 3D-quantitative coronary angiography (QCA) models appears to provide useful prognostic information and identifies high-risk patients and lesions. However, conventional computational fluid dynamics (CFD) analysis is cumbersome limiting its application in the clinical arena. This report introduces a user-friendly software that allows real-time WSS computation and examines its reproducibility and accuracy in assessing WSS distribution against conventional CFD analysis. MethodsFrom a registry of 414 patients with borderline negative fractional flow reserve (0.81–0.85), 100 lesions were randomly selected. 3D-QCA and CFD analysis were performed using the conventional approach and the novel CAAS Workstation WSS software, and QCA as well as WSS estimations of the two approaches were compared. The reproducibility of the two methodologies was evaluated in a subgroup of 50 lesions. ResultsA good agreement was noted between the conventional approach and the novel software for 3D-QCA metrics (ICC range: 0.73–0-93) and maximum WSS at the lesion site (ICC: 0.88). Both methodologies had a high reproducibility in assessing lesion severity (ICC range: 0.83–0.97 for the conventional approach; 0.84–0.96 for the CAAS Workstation WSS software) and WSS distribution (ICC: 0.85–0.89 and 0.83–0.87, respectively). Simulation time was significantly shorter using the CAAS Workstation WSS software compared to the conventional approach (4.13 ± 0.59 min vs 23.14 ± 2.56 min, p < 0.001). ConclusionCAAS Workstation WSS software is fast, reproducible, and accurate in assessing WSS distribution. Therefore, this software is expected to enable the broad use of WSS metrics in the clinical arena to identify high-risk lesions and vulnerable patients.

Comparison of diagnostic accuracy measures of novel 3D quantitative coronary angiography based software and diastolic pressure ratio for fractional flow Reserve. A single center pooled analysis of FAST EXTEND and FAST II studies.

Comparison of diagnostic accuracy measures of novel 3D quantitative coronary angiography based software and diastolic pressure ratio for fractional flow Reserve. A single center pooled analysis of FAST EXTEND and FAST II studies.

Feasibility, reproducibility and characteristics of coronary bifurcation type assessment by three-dimensional optical coherence tomography.

To investigate the characteristics of coronary artery bifurcation type (parallel or perpendicular type) using three-dimensional (3D) optical coherence tomography (OCT), and determine the feasibility, reproducibility, assessment time and correlation with bifurcation angles measured by 3D quantitative coronary angiography (QCA). We evaluated 60 lesions at the coronary bifurcation that were treated by main vessel (MV) stenting with kissing balloon inflation (KBI) under OCT/optical frequency domain imaging (OFDI) guidance. Inter- and intra-observer agreement regarding the assessment of 3D bifurcation types were 0.88 and 0.94, respectively. The assessment times of 3D-OCT bifurcation type with OCT and OFDI were within about 30 seconds. 3D-OCT bifurcation types showed the greatest correlation with the distal bifurcation angle assessed by 3D-QCA among the three bifurcation angles (distal bifurcation angle, proximal bifurcation angle and main vessel angle), and the optimal cut-off distal bifurcation angle to predict a perpendicular type bifurcation, as determined by ROC analysis, was 51.0° (AUC 0.773, sensitivity 0.80, specificity 0.67). Based on this cut-off value for the distal bifurcation angle (51°), the diagnostic accuracy for perpendicular type bifurcation in cases with a BA ≥ 51° (n = 34) was 70.6% (24/34) and that of the parallel type bifurcation in cases of BA < 51° (n = 26) was 76.9% (20/26). Performing 3D-OCT for assessment of coronary artery bifurcation type is feasible and simple, and can be done in a short time with high reproducibility.

720 Angiography-derived index of microvascular resistance (IMR-angio) in Takotsubo syndrome

Abstract Aims Coronary microvascular dysfunction (CMD) has been proposed as a key driver in the etiopathogenesis of Takotsubo syndrome (TTS), likely related to an ‘adrenergic storm’ upon a susceptible microvascular circulation. The aim of our manuscript was to assess and quantify coronary microvascular disfunction in patients with TTS using the recently developed angiography-derived index of microcirculation (IMRangio) and evaluate its correlation with clinical and instrumental presentation. Methods and results 41 consecutive TTS patients were retrospectively analysed. Three different formulas for compute non-hyperemic IMRangio (NH-IMRangio) derived by 3D-Quantitative Coronary Angiography (3D-QCA) and Quantitative Flow Reserve (QFR) analysis were used according to each fluidodynamic mathematical expression as reported by respective authors. CMD was defined as an IMRangio ≥25. Moreover, correlation between NH-IMRangio and clinical presentation and a comparation between the three formulas were provided. Median age was 76 years, 85.7% were women and mean LVEF at first echocardiogram was 41.2%. All patients presented CMD with NH-IMRangio ≥25 in at least one territory. Mean NH-IMRangio was higher in Left Anterior Descending artery (LAD) than Circumflex artery (CX) and Right Coronary artery (RCA) with either Oxford-NH-IMRangio (52.7 ± 18.6 vs. 35.3 ± 13.6 vs. 41.4 ± 15.1, P-value &amp;lt; 0.001), Madrid-NH-IMRangio (47.2 ± 17.3 vs. 31.8 ± 12.2 vs. 37.3 ± 13.7, P-value &amp;lt;0.001) or Ferrara-NH-IMRangio (52.7 ± 19 vs. 36.1 ± 14.1 vs. 41.8 ± 16.1, P-value &amp;lt; 0.001). Furthermore, the mean values of NH-IMRangio were not significantly different using the different equations (OXFvsMAD P-value = 0.1930; OXFvsFER P-value = 0.9609; MADvsFER P-value = 0.2144). NH-IMRangio in LAD territory was significantly higher in pts presenting with LVEF impairment (≤40%) than pts with preserved ventricular global function (mean NH-IMRangio LAD 59.3 ± 18.1 vs. 46.3 ± 16, P-value = 0.030). NH-IMRangio assessed in LAD territory showed a trend towards linear association with LVEF (Figure 1). 720 Figure Conclusions CMD, assessed with NH-IMRangio, is a common finding in TTS and it is associated with LVEF dysfunction and LVEF recovery. The validated formulas for NH-IMRangio computation have a superimposable diagnostic performance and accuracy.

TCT-395 Diagnostic Performance of 3D Quantitative Coronary Angiography Vessel FFR With Diastolic Pressure Ratio: A Pooled Analysis of the FAST EXTEND and FAST II Studies

TCT-395 Diagnostic Performance of 3D Quantitative Coronary Angiography Vessel FFR With Diastolic Pressure Ratio: A Pooled Analysis of the FAST EXTEND and FAST II Studies

Moving shear stress towards the clinic: preclinical comparison of optical coherence tomography-based versus angiography-based time-averaged wall shear stress estimations

Abstract Introduction Identification of coronary atherosclerotic plaques at risk of causing future acute coronary syndromes remains a major unmet clinical challenge. The addition of vessel biomechanics to intracoronary imaging derived evaluation of plaque morphology, improves identification of plaques likely to develop high risk features. We and others have developed a framework for intracoronary imaging (optical coherence tomography [OCT]) based 3D reconstructions of coronary arteries for computational fluid dynamics (CFD) simulations of shear stress, which are considered the current gold standard approach for quantification of coronary arterial haemodynamics. However, these approaches are time consuming and computationally intensive, resulting in a barrier to clinical uptake. Purpose Determination of time averaged wall shear stress (TAWSS) based on 3D coronary geometries from non-invasive 3D Quantitative Coronary Angiography (3D-QCA) has recently been developed (Pie Medical Imaging, Netherlands), which enables results of shear stress simulations to be available within 30 minutes. We sought to compare TAWSS determined from 3D-QCA with gold standard OCT-based CFD simulations in both normal and stenotic arteries in minipigs. Methods 15 normal and 5 stenotic minipig coronary arteries were studied. Anatomically matched 3D arterial geometries were reconstructed from 3D-QCA and OCT using common centrelines. Boundary conditions for simulations included directly measured inlet blood velocities; parabolic inlet flow profiles, zero pressure outlet; no-slip arterial walls; blood density: 1.05 g/ml; blood dynamic viscosity: 0.035 g/cm.s. Blood was modelled as Newtonian. 3D-QCA TAWSS was obtained with a Kratos Multi-Physics CFD solver. OCT-based simulations were performed using Abaqus/CFD v6.14. TAWSS was calculated for 80 axially matched segments for both methods (1200 and 400 paired comparisons for normal and stenotic arteries, respectively). Data were analysed using Bland-Altman and Wilcoxon matched-pairs signed ranked tests. Results Computation times for 3D-QCA and OCT-based CFD were approximately 30 minutes and 2 hours respectively. Axial profiles of TAWSS were similar between the two methods and there was agreement in TAWSS magnitudes and narrow 95% limits of agreement (Figure 1 and Figure 2). Using co-registered TAWSS maps generated by each method, we find similar spatial regional distributions of TAWSS in both normal and stenotic arteries. Conclusions Our data suggest that 3D-QCA based TAWSS is feasible in both normal and stenotic arteries. Spatial TAWSS distributions between the two methods are similar with agreement in matched TAWSS comparisons, though there are some small systematic differences in the absolute values of TAWSS, due to different resultant arterial geometries. These encouraging data suggest that further clinical evaluation of rapid TAWSS from 3D-QCA is warranted, which may facilitate clinical adoption of TAWSS assessment. Funding Acknowledgement Type of funding sources: Public grant(s) – EU funding. Main funding source(s): Medical Research Council

Quantitative evaluation and comparison of coronary artery characteristics by 3D coronary volume reconstruction

Non-atherosclerotic abnormalities of vessel calibre, aneurysm and ectasia, are challenging to quantify and are often overlooked in qualitative reporting. Utilising a novel 3-dimensional (3D) quantitative coronary angiography (QCA) application, we have evaluated the characteristics of normal, diabetic and aneurysmal or ectatic coronary arteries. We selected 131 individuals under 50 years-of-age, who had undergone coronary angiography for suspected myocardial ischaemia between 1st January 2011 and 31st December 2015, at the Bristol Heart Institute, Bristol, UK. This included 42 patients with angiographically normal coronary arteries, 36 diabetic patients with unobstructed coronaries, and 53 patients with abnormal coronary dilatation (aneurysm and ectasia). A total of 1105 coronary segments were analysed using QAngio XA 3D (Research Edition, Medis medical imaging systems, Leiden, The Netherlands). The combined volume of the major coronary arteries was significantly different between each group (1240 ± 476 mm3 diabetic group, 1646 ± 391 mm3 normal group, and 2072 ± 687 mm3 abnormal group). Moreover, the combined coronary artery volumes correlated with patient body surface area (r = 0.483, p < 0.01). Inter-observer variability was assessed and intraclass correlation coefficient of the total coronary artery volume demonstrated a low variability of 3D QCA (r = 0.996, p < 0.001). Dedicated 3D QCA facilitates reproducible coronary artery volume estimation and allows discrimination of normal and diseased vessels.

Endocan expression correlated with total volume of coronary artery dilation in patients with coronary artery ectasia.

IntroductionInflammation and angiogenesis disturbances are considered as factors contributing to the development of coronary artery ectasias (CAE). Endocan (endothelial cell-specific molecule-1 – ESM-1) regulates both inflammatory and angiogenetic processes. However, there are no data about the correlation between endocan level and the severity of CAE measured with total volume of coronary artery dilation.AimTo assess whether the severity of the inflammatory process measured as endocan concentration correlates with the total volume of CAE.Material and methodsWe selected prospectively a total of 43 consecutive patients with coronary artery ectasia from 2240 patients who underwent coronary angiography in our center. Determination of endocan was performed by using the Human Endothelial cell-specific Molecule 1 (ECSM1/ENDOCAN) ELISA Kit. 3D QCA (three-dimensional quantitative coronary angiography) was used for coronary lesion and aneurysm quantification. The total volume of dilation was defined as the volume of all aneurysms and ectasias of coronary arteries in 1 patient.ResultsThe mean volume of all aneurysms in 1 patient was 677 ±878.7 mm3. The total aneurysm volume was positively strongly correlated with endocan concentration (Pearson correlation coefficient: 0.811; 2-tailed p < 0.001).ConclusionsEndocan is a potential marker of vascular wall damage mainly as a result of inflammation in the course of atherosclerosis, but also vascular remodeling as a result of a disturbance of pro- and anti-angiogenic processes. Endocan level reflects the intensity of the above processes and therefore correlates with the severity of CAE, measured as the total volume of dilation.

Effects of different non-Newtonian models on unsteady blood flow hemodynamics in patient-specific arterial models with in-vivo validation

The aim of this study is to demonstrate the implications of using different blood rheological models in the simulation of blood flow dynamics in atherosclerotic coronary arteries. Computational fluid dynamics simulation was performed using three-dimensional (3D) patient-specific models of diseased left anterior descending (LAD) coronary arteries with varying degrees of stenosis severity. The three-dimensional arterial models were reconstructed from 3D quantitative coronary angiography, and input flow conditions were prescribed with blood flow conditions measured in-vivo. Different blood viscosity models were used for the simulations, and they include Newtonian and also non-Newtonian models such as Bingham, Carreau, Carreau-Yasuda, Casson, modified Casson, Cross, modified Cross, simplified Cross, Herschel Bulkley, Kuang-Luo (K-L), PowellErying, modified PowellErying, Power-law, Quemada and Walburn-Schneck models. Results from this study show that the time-averaged velocity at the centre of the arteries produced in the CFD simulations that uses the Carreau, modified Casson or Quemada blood viscosity models corresponded exceptionally well with the clinical measurements regardless of stenosis severities and hence, highlights the usefulness of these models to determine the potential determinants of blood vessel wall integrity such as dynamic blood viscosity, blood velocity and wall shear stress.

P869Predictive value of the endothelial shear stress distribution in three-dimensional quantitative coronary angiography models in detecting vulnerable plaques

Abstract Background Low Endothelial shear stress (ESS) is a well-known instigator of coronary atherosclerosis. Prospective intravascular ultrasound (IVUS)-based imaging studies with computational fluid dynamic analysis revealed its predictive merit in-vivo. However, whether coronary modelling derived from quantitative coronary angiography (QCA) is equally effective in detecting high-risk plaques remains to be established. Purpose To examine the value of endothelial shear stress (ESS) estimated in three-dimensional (3D) QCA models in detecting plaques that are likely to progress and cause events. Method We analysed the baseline intravascular ultrasound virtual histology (IVUS-VH) and angiographic data from 28 non-culprit lesions with a vulnerable phenotype (i.e., fibroatheroma or thin cap fibroatheroma) that caused major adverse cardiac events or required revascularization (nc-MACE-R) at 5-year follow-up and from a control group of 119 vulnerable plaques that remained quiescent. The segments studied by IVUS-VH at baseline were reconstructed using 3D-QCA software and in the obtained geometries blood flow simulation was performed and we estimated the resting Pd/Pa across the vulnerable plaque and the mean ESS values in 3mm sub-segments. A propensity score was built by the baseline plaque characteristics and the hemodynamic indices and its efficacy in detecting nc-MACE-R lesions was examined. Results Nc-MACE-R lesions were longer (32.5mm [18.0, 41.6], vs. 19.6mm [12.7, 31.3], p=0.03), had smaller minimum lumen area (MLA) (3.65mm2 [3.26, 4.36] vs. 5.03mm2 [3.98, 6.66], p&lt;0.01), increased plaque burden (PB) (69.4% [63.5, 72.0] vs. 60.8% [53.7, 66.5], p&lt;0.01), were exposed to higher ESS (9.40Pa [6.3, 12.5] vs. 4.1Pa [3.0, 6.9], p&lt;0.01), and exhibited a lower resting Pd/Pa (0.97 [0.95, 0.98] vs. 0.98 [0.97, 0.99], p&lt;0.01]. In multivariable analysis the only independent predictor of nc-MACE-R was the maximum 3mm ESS value (hazard ratio: 1.08 [1.02, 1.16], P=0.016). Lesions exposed to high ESS (&gt;4.95Pa) with a high-risk anatomy (MLA&lt;4mm2and PB&gt;70%) had a higher nc-MACE-R rate (53.8%) than those with a low-risk anatomy exposed to high ESS (31.6%) or those exposed to low ESS that had high (20.0%) or low-risk anatomy (7.1%, P&lt;0.001). Conclusion In the present study, 3D-QCA-derived local hemodynamic variables provided useful prognostic information and in combination with lesion anatomy enabled more accurate identification of nc-MACE-R lesions. Further research in a larger number of patients is need to confirm these findings before the conduction of large scale prospective studies that will combine intravascular imaging and 3D-QCA modelling to more accurately detect vulnerable plaques.

Quantitative myocardial perfusion in coronary artery disease: A perfusion mapping study.

BackgroundCardiac MR stress perfusion remains a qualitative technique in clinical practice due to technical and postprocessing challenges. However, automated inline perfusion mapping now permits myocardial blood flow (MBF, ml/g/min) quantification on‐the‐fly without user input.PurposeTo investigate the diagnostic performance of this novel technique in detecting occlusive coronary artery disease (CAD) in patients scheduled to undergo coronary angiography.Study TypeProspective, observational.SubjectsFifty patients with suspected CAD and 24 healthy volunteers.Field Strength1.5T.Sequence"Dual" sequence multislice 2D saturation recovery.AssessmentAll patients underwent cardiac MR with perfusion mapping and invasive coronary angiography; the healthy volunteers had MR with perfusion mapping alone.Statistical TestsComparison between numerical variables was performed using an independent t‐test. Receiver operator characteristic (ROC) curves were generated for transmyocardial, endocardial stress MBF, and myocardial perfusion reserve (MPR, the stress:rest MBF ratio) to diagnose severe (>70%) stenoses as measured by 3D quantitative coronary angiography (QCA). ROC curves were compared by the method of DeLong et al.ResultsCompared with volunteers, patients had lower stress MBF and MPR even in vessels with <50% stenosis (2.00 vs. 3.08 ml/g/min, respectively). As stenosis severity increased (<50%, 50–70%, >70%), MBF and MPR decreased. To diagnose occlusive (>70%) CAD, endocardial and transmyocardial stress MBF were superior to MPR (area under the curve 0.92 [95% CI 0.86–0.97] vs. 0.90 [95% CI 0.84–0.95] and 0.80 [95% CI 0.72–0.87], respectively). An endocardial threshold of 1.31 ml/g/min provided a per‐coronary artery sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of 90%, 82%, 50%, and 98%, with a per‐patient diagnostic performance of 100%, 66%, 57%, and 100%, respectively.Data ConclusionPerfusion mapping can diagnose occlusive CAD with high accuracy and, in particular, high sensitivity and NPV make it a potential "rule‐out" test. Level of Evidence: 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2019;50:756–762.

Diagnostic Accuracy of Quantitative Flow Ratio (QFR) Compared to Instantaneous Flow Wave Free Ratio (iFR) and DILEMMA Score to Predict Fractional Flow Reserve (FFR)

Background: Quantitative flow ratio (QFR) is a novel 3D quantitative coronary angiography and computational fluid dynamics technique to calculate fractional flow reserve (FFR). The DILEMMA score is a recent angiographic technique that has incremental predictive value over diameter stenosis to predict FFR. Unlike FFR, instantaneous wave-free ratio (iFR), diastolic pressure ratio (dPR), QFR and DILEMMA score do not require a pressure-wire or hyperaemia induction. Purpose: To compare the diagnostic accuracy of QFR compared to iFR, dPR and DILEMMA score to predict FFR. Methods: Patients who underwent invasive coronary angiography and FFR assessments were retrospectively studied. iFR and dPR were derived from FFR pressure tracings using a proprietary technique. QFR was computed using a commercially available software. Results: 85 lesions (33% FFR significant) were included. Mean FFR was 0.86 ± 0.09. QFR (rs = 0.801; p < 0.001), iFR (rs = 0.710; p < 0.001), dPR25-75 (rs = 0.715; p < 0.001) and DILEMMA score (H test statistic = 40.56, p < 0.001) were strongly correlated with FFR. QFR <0.8 had a sensitivity, specificity, PPV and NPV of 84%, 92%, 76% and 95% respectively of predicting significant FFR (<0.001). On comparison of AUC, QFR (0.94) is a better predictor of FFR compared to iFR (0.88), DPR (0.88) and DILEMMA score (0.9), p < 0.001. Conclusion: QFR is a better predictor of FFR compared to iFR, DPR and DILEMMA score. Further studies are required to confirm its diagnostic accuracy as well as its cost effectiveness for routine clinical practice.

Referral of patients for fractional flow reserve using quantitative flow ratio.

Quantitative flow ratio (QFR) is a recently developed technique to calculate fractional flow reserve (FFR) based on 3D quantitative coronary angiography and computational fluid dynamics, obviating the need for a pressure-wire and hyperaemia induction. QFR might be used to guide patient selection for FFR and subsequent percutaneous coronary intervention (PCI) referral in hospitals not capable to perform FFR and PCI. We aimed to investigate the feasibility to use QFR to appropriately select patients for FFR referral. Patients who underwent invasive coronary angiography in a hospital where FFR and PCI could not be performed and were referred to our hospital for invasive FFR measurement, were included. Angiogram images from the referring hospitals were retrospectively collected for QFR analysis. Based on QFR cut-off values of 0.77 and 0.86, our patient cohort was reclassified to 'no referral' (QFR ≥0.86), referral for 'FFR' (QFR 0.78-0.85), or 'direct PCI' (QFR ≤0.77). In total, 290 patients were included. Overall accuracy of QFR to detect an invasive FFR of ≤0.80 was 86%. Based on a QFR cut-off value of 0.86, a 50% reduction in patient referral for FFR could be obtained, while only 5% of these patients had an invasive FFR of ≤0.80 (thus, these patients were incorrectly reclassified to the 'no referral' group). Furthermore, 22% of the patients that still need to be referred could undergo direct PCI, based on a QFR cut-off value of 0.77. QFR is feasible to use for the selection of patients for FFR referral.