Functional Significance Of Coronary Stenosis Research Articles

An Overview of Computational Coronary Physiology Technologies Based on Medical Imaging and Artificial Intelligence.

This article reviews four new technologies for assessment of coronary hemodynamics based on medical imaging and artificial intelligence, including quantitative flow ratio (QFR), optical flow ratio (OFR), computational fractional flow reserve (CT-FFR) and artificial intelligence (AI)-based instantaneous wave-free ratio (iFR). These technologies use medical imaging such as coronary angiography, computed tomography angiography (CTA), and optical coherence tomography (OCT), to reconstruct three-dimensional vascular models through artificial intelligence algorithms, simulate and calculate hemodynamic parameters in the coronary arteries, and achieve non-invasive and rapid assessment of the functional significance of coronary stenosis. This article details the working principles, advantages such as non-invasiveness, efficiency, accuracy, limitations such as image dependency, and assumption restrictions, of each technology. It also compares and analyzes the image dependency, calculation accuracy, calculation speed, and operation simplicity, of the four technologies. The results show that these technologies are highly consistent with the traditional invasive wire method, and shows distinct advantages in terms of accuracy, reliability, convenience and cost-effectiveness, but there are also factors that affect accuracy. The results of this review demonstrates that AI-based iFR technology is currently one of the most promising technologies. The main challenges and directions for future development are also discussed. These technologies bring new ideas for the non-invasive assessment of coronary artery disease, and are expected to promote the technological progress in this field.

Comparison of vessel fractional flow reserve with invasive resting full-cycle ratio in patients with intermediate coronary lesions

BackgroundVessel fractional flow reserve (vFFR) is a novel angiography-derived index for the assessment of myocardial ischemia without the need for pressure wires and hyperemic agents. vFFR has demonstrated very good diagnostic performance compared with the hyperemic index fractional flow reserve (FFR). The aim of this study was to compare vFFR to the non-hyperemic pressure ratio resting full-cycle ratio (RFR). MethodsThis was a retrospective, observational, single-center study of an all-comer cohort undergoing RFR assessment. Invasive coronary angiography was obtained without a dedicated vFFR acquisition protocol, and vFFR calculation was attempted in all vessels interrogated by RFR (1483 lesions of 1030 patients). ResultsvFFR could be analyzed in 986 lesions from 705 patients. Median diameter stenosis was 37% (interquartile range (IQR): 30.0–44.0%), vFFR 0.86 (IQR: 0.81–0.91) and RFR 0.94 (IQR: (0.90–0.97). The correlation between vFFR and RFR was strong (r = 0.70, 95% confidence interval (CI): 0.66–0.74, p < 0.001). Using RFR ≤0.89 as reference, the sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy for vFFR were 77%, 93%, 77%, and 92% and 89%. vFFR yielded a high area under the curve (AUC) of 0.92 (95% CI: 0.90–0.94). The good diagnostic performance of vFFR was confirmed among subgroups of patients with diabetes, severe aortic stenosis, female gender and lesions located in the left anterior descending artery. ConclusionvFFR has a high diagnostic performance taking RFR as the reference standard for evaluating the functional significance of coronary stenoses.

Evaluation of coronary artery side branches (SB) with Quantitative Flow Ratio (QFR) by comparing the use of recommended angiographic projections with routine angiographic projections as Reference

Abstract Background Contrast-flow quantitative flow ratio (QFR) is a novel, noninvasive method for the quantitative evaluation of coronary physiology using computational fluid dynamics based on 3D vessel reconstruction in angiograms. Computing this 3D-model with analyzing the dynamics of the contrast medium flow with a specialized algorithm, the software computes the virtual FFR. This new technique has shown a high accuracy in determining the functional significance of coronary stenosis of the three main epicardial coronary arteries using the gold standard FFR as reference. However, QFR data for the evaluation of coronary side branches (SB) are scarce. Therefore, the study aimed to determine the feasibility of this novel method to analyze SB and to characterize optimal viewing angles for evaluation using QFR. Methods A total of 87 patients, who underwent invasive coronary angiography with routine core lab projections, were enrolled in the study and were analyzed retrospectively by two certified experts with the software QAngio XA 3D 3.2. In addition, 37 patients were enrolled prospectively using coronary angiography projections recommended for the virtual QFR-Analysis. Quantitative Analysis was performed only for SB with a maximum lumen diameter (MLD) of ≥2mm. The following outcome parameters were analyzed: baseline characteristics, anatomical SB parameters such as MLD (mm) and vessel length (VL; mm) of the SB, result of the QFR-computation and procedure parameters, such as use of applicated contrast medium and fluoroscopy time. Results 187 side branches (obtuse marginal [OM], diagonal branch [DB], intermediate artery [IA], posterolateral branch [PLB] and posterior descending artery [PDA]) were analyzed using QFR. Out of 87 patients undergoing an invasive coronary angiography with routine core lab projections with 244 SB ≥2mm, 123 SB (55%) were computable with the use of QFR. In the prospective cohort of 37 patients with recommended angiographic projections for QFR analysis of main branches, 75 SB ≥2mm were found. 64 of the 75 SB (84%) were computable with the use of QFR. The use of recommended projections led to an overall higher evaluability of SB (85% vs. 55%). The data show that the fluoroscopy time for recommended QFR projections was not significantly different as the time for routine cath lab projections (3.7±2.2 vs. 4.6±3, p=2.69). The study shows a significant increase of the amount of contrast medium used for QFR projections (55.4±24.2 vs. 87.9±43.7, p&amp;lt;0.01). Conclusion To our knowledge this is the first study evaluating QFR for SB analysis. QFR is feasible for the routine assessment of side branches (SD) with MLD ≥2mm. The use of recommended projections significantly improved the quality of the QFR SB analysis apart from PDA, without increasing the fluoroscopy time during coronary angiography. Overall QFR could increase the use of physiologically guided coronary interventions, not only for the main epicardial vessels, but also for the SB. Funding Acknowledgement Type of funding sources: None.

Relation of quantitative flow ratio with transit time coronary artery bypass graft flow measurement.

BackgroundQuantitative flow ratio (QFR) is a new functional index to assess the functional significance of coronary stenosis. While whether there is an association between QFR and transit-time flow measurement (TTFM) parameters of the target coronary artery has not been well addressed.MethodsA total of 89 patients receiving the in situ left internal thoracic artery (LITA) grafts to the left anterior descending artery (LAD), and 19 patients undergoing the saphenous vein grafts (SVG) were enrolled in this retrospective study. The QFR value of the LAD was evaluated preoperatively. According to the QFR values, patients with the LITA to the LAD bypass grafts were divided into two groups (group A1: QFR < 0.75, group A2: QFR ≥ 0.75), and SVG patients were divided into two groups (V1 group: QFR < 0.75, V2 group: QFR ≥ 0.75).ResultsIn groups A1 and A2, respectively, median graft flow (Qm) was 44 (34) mL/minute and 26.5 (30.0) ml/minute; median pulsatility index (PI) was 2.00 (1.00) and 2.65 (0.90). Significant differences were observed in Qm (P = 0.034) and PI (P = 0.030). And the correlation coefficients of the TTFM variables with QFR were Qm: r = r = −0.226, (P = 0.036), PI: r = 0.265 (P = 0.012) among the LITA to LAD population.ConclusionTTFM variables, especially the PI, of the LITA in situ graft to the LAD during Coronary artery bypass grafting (CABG) are strongly affected by preoperative QFR values. Moreover, in functionally mild coronary stenosis, the chance of competitive flow increases.

Novel study and applications of CT angiography derived fractional flow reserve in China

CT angiography derived fractional flow reserve (CT-FFR) has been an important tool for evaluating functional significance of coronary stenosis since 2011, promoting coronary CT angiography (CCTA) from the era of traditional anatomical evaluation to a new era of functional evaluation,playing a key role in guiding clinical decisions and prognostic evaluation of coronary artery disease. This review focuses on the innovative research and contributions of Chinese scholars' in CT-FFR filed, including homemade techniques, extending clinical applications and generalization of CT-FFR.

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 performance of quantitative flow ratio versus fractional flow reserve and resting full-cycle ratio in intermediate coronary lesions

BackgroundQuantitative flow ratio (QFR) is a novel angiography-derived index aimed to assess the functional relevance of coronary stenoses without pressure wires and adenosine. Good diagnostic yield with the hyperemic fractional flow reserve (FFR) have been reported, while data on the comparison of QFR to non-hyperemic pressure ratios (NHPR) are scarce. MethodsIn this retrospective, observational and single-center study with a large population representative of the real practice, we assessed and compared the diagnostic performance of contrast flow (cQFR) and fixed flow (fQFR) QFR against the NHPR resting full-cyle ratio (RFR) using FFR as reference standard. ResultsA total of 626 lesions from 544 patients were investigated. Mean diameter stenosis, FFR, cQFR, fQFR and RFR were 44.8%, 0.842, 0.847, 0.857 and 0.912, respectively. The correlation between cQFR and FFR was stronger (r = 0.830, P < 0.001) compared to that between FFR and RFR (r = 0.777, P < 0.001) and between cQFR and RFR (r = 0.687, P < 0.001). Using FFR ≤0.80 as reference, the sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy for cQFR were 82%, 95%, 87%, 92%, and 91%, respectively. cQFR displayed a higher area under the curve (AUC) than fQFR and RFR (0.938 vs. 0.891 vs. 0.869, P < 0.01). The good diagnostic yield of cQFR appeared to be maintained in different clinical subsets including female gender, aortic valve stenosis and atrial fibrillation, and in different anatomical subsets including focal and non-focal lesions. ConclusioncQFR has a high and better diagnostic performance than the NHPR RFR in predicting FFR-based functional significance of coronary stenoses.

Validity and correlation of quantitative flow ratio with fractional flow reserve for assessment of intermediate coronary lesions

Background The angiographic percent diameter stenosis (%DS) do not assess the physiological significance of epicardial coronary stenosis. The currently practised physiological indices require pressure wires with or without adenosine-induced hyperaemia. Quantitative flow ratio (QFR) is an angiography-based method to determine the functional significance of coronary stenosis. The present study aimed to analyse the diagnostic performance of QFR in comparison to fractional flow reserve (FFR) in intermediate coronary lesions. Materials and methods It was a single centre retrospective study to analyse the diagnostic performance of offline QFR with the previously performed FFR in the last six years. A total of 56 interrogated vessels were included for the analysis. Offline QFR analysis was performed and correlated with FFR values in the intermediate coronary stenoses. Results The mean age of the study population was 62.4 ± 9.1 years, including 81% men. The left anterior descending artery (50%) was the most common analysed vessel followed by left circumflex (27%) and right coronary (21%) arteries. The mean % DS and % area stenosis were 45.25 ± 11.22% and 57.45% ± 16.25%, respectively. The mean FFR and QFR values were 0.83 ± 0.06 and 0.82 ± 0.10, respectively. A strong positive correlation was found between FFR and QFR with a Spearman correlation coefficient of 0.56. Receiver operating curve analysis for QFR and %DS with a FFR cut off value <0.80 showed an area under the curve of 0.97 and 0.77, respectively. The sensitivity, specificity and diagnostic accuracy of QFR were 87.5%, 95% and 92.8%, respectively. There was a discordance in four vessels (7.1%) between QFR and FFR. Conclusion QFR has a good diagnostic performance in comparison to the gold standard FFR for physiological assessment of intermediate lesions. Its performance is significantly better than the anatomical % DS (p < 0.001).

Bifurcation functional significance score as predictor of mortality: a validating study

Considerable progress has been made in the treatment of coronary bifurcation stenosis. Anatomical characteristics of the vessel and lesion, however, fail to give information about the functional significance of the bifurcation stenosis. To the best of our knowledge, there is no study that systematically establishes the baseline functional significance of coronary stenosis and its effect on procedural and clinical outcomes. Patients with significant angiographic bifurcation lesions defined as diameter stenosis > 50% in main vessel and/or side branch were included. FFR was performed in main vessel (MV) and side branch (SB) before and after percutaneous coronary intervention (PCI). 169 patients from Fiesta study (derivation cohort) and 555 patients from prospective bifurcation registry (clinical effect cohort) were analyzed to validate angiographic prediction score (BFSS) used to determine the potentially functional significance of coronary bifurcation stenosis. Bifurcation functional significance score (including the following parameters—SYNTAX ≥ 11, SB/MB BARI score, MV %DS ≥ 55%, main branch (MB) %DS ≥ 65%, lesion length ≥ 25 mm) with a maximum value of 11 was developed. A cut-off value of 6.0 was shown to give the best discriminatory ability—with accuracy 87% (sensitivity 77%, specificity 96%, p < 0.001). There was also a significant difference in all-cause mortality between patients with BFSS ≥ 6.0 vs. BFSS < 6.0–25.5% vs. 18.4%, log-rank p = 0.001 as well as cardiac mortality: BFSS ≥ 6.0 vs. BFSS < 6.0–17.7% vs. 14.5%, log-rank (p = 0.016). The cardiac mortality was significantly lower in patients with smaller absolute SB territory, p = 0.023. An angiographic score (BFSS) with good discriminatory ability to determine the functional significance of coronary bifurcation stenosis was developed. The value for BFSS ≥ 6.0 can be used as a discriminator to define groups with higher risk for all-cause and cardiac mortality. Also, we found that the smaller side branches pose greater mortality risk.

Diagnostic performance of QFR vs FFR

Fractional flow reserve (FFR) is an invasive assessment of the functional significance of coronary stenosis utilizing a pressure wire. Quantitative flow ratio (QFR) is an angiography-based approximate of FFR. This new technology appears to be accurate and may be a useful alternative to FFR.

Baseline troponin-T is powerful predictor of mortality after coronary bifurcation stenting

Abstract Introduction Considerable progress has been made in the treatment of coronary bifurcation stenosis. Anatomical characteristics of the lesion, however, fail to give information about the functional significance of the bifurcation stenosis. There is no study that systematically establishes the baseline functional significance of coronary stenosis and its effect on procedural and clinical outcomes. Methods Patients with significant angiographically bifurcation lesions defined as diameter stenosis &amp;gt;50% in main vessel and/or side branch were included. FFR was performed in main vessel (MV) and side branch (SB) before and after percutaneous coronary intervention (PCI). If FFR was ≤0.80 the lesion was considered functionally significant, and patients underwent PCI. For the group with FFR &amp;gt;0.80 – intervention was deferred. All patients were followed-up for vital status every 3 months. Cox regression analysis was performed to identify independent predictors of all-cause and cardiovascular death. The local ethics committee approved the study and patients signed informed consent for participation into registry. Results For mean follow-up of 38±18 months (median 40, IQR 23–55 months) all-cause mortality was numerically lower: 8.5% (n=7/82) in deferred group and 12.6% in stented group (n=11/76, p=0.387). The cardiac mortality was also numerically lower, but statistically not significant (9.8%, n=8/82 vs. 11.5%, n=10/88, p=0.714). On multivariate model, independent predictors were mitral regurgitation &amp;gt;1st degree – HR=1.778 (CI 1.100–2.874, p=0.019); dyslipidemia HR=0.765 (CI 0.594–0.985, p=0.038); hemoglobin concentration – HR=0.976 (CI 0.964–0.988, p&amp;lt;0.001); pre-PCI serum troponin ≥0.010 ng/ml – HR=2.702 (CI 1.451–5.032, p=0.002). On multivariate analysis, the following factors were identified as independent predictors of cardiac mortality: age – HR=1.035 (CI 1.009–1.062, p=0.009); diabetes – HR=1.789 (CI 1.089–2.962, p=0.024); dyslipidemia treated with statin – HR=0.667 (CI 0.515–0.863, p=0.002); LV posterior wall thickness – HR=1.230 (CI 1.062–1.424, p=0.006); mitral regurgitation more than 1st degree – HR=1.763 (CI 1.065–2.917, p=0.027); troponin pre-PCI ≥0.010 ng/ml – HR=2.498 (CI 1.228–5.081, p=0.011); true bifurcation lesion – HR=1.820 (CI 1.026–3.229, p=0.040); SBBARI score &amp;lt;10% – HR=1.715 (CI 1.049–2.804, p-0.031). Conclusion Baseline high-sensitive troponin T value is a strong predictor for both all cause and cardiac mortality in patients undergoing coronary bifurcation lesion PCI. Funding Acknowledgement Type of funding sources: Public hospital(s). Main funding source(s): Alexandrovska University Hospital

Non-invasive imaging software to assess the functional significance of coronary stenoses: a systematic review and economic evaluation.

QAngio® XA 3D/QFR® (three-dimensional/quantitative flow ratio) imaging software (Medis Medical Imaging Systems BV, Leiden, the Netherlands) and CAAS® vFFR® (vessel fractional flow reserve) imaging software (Pie Medical Imaging BV, Maastricht, the Netherlands) are non-invasive technologies to assess the functional significance of coronary stenoses, which can be alternatives to invasive fractional flow reserve assessment. The objectives were to determine the clinical effectiveness and cost-effectiveness of QAngio XA 3D/QFR and CAAS vFFR. We performed a systematic review of all evidence on QAngio XA 3D/QFR and CAAS vFFR, including diagnostic accuracy, clinical effectiveness, implementation and economic analyses. We searched MEDLINE and other databases to January 2020 for studies where either technology was used and compared with fractional flow reserve in patients with intermediate stenosis. The risk of bias was assessed with quality assessment of diagnostic accuracy studies. Meta-analyses of diagnostic accuracy were performed. Clinical and implementation outcomes were synthesised narratively. A simulation study investigated the clinical impact of using QAngio XA 3D/QFR. We developed a de novo decision-analytic model to estimate the cost-effectiveness of QAngio XA 3D/QFR and CAAS vFFR relative to invasive fractional flow reserve or invasive coronary angiography alone. Scenario analyses were undertaken to explore the robustness of the results to variation in the sources of data used to populate the model and alternative assumptions. Thirty-nine studies (5440 patients) of QAngio XA 3D/QFR and three studies (500 patients) of CAAS vFFR were included. QAngio XA 3D/QFR had good diagnostic accuracy to predict functionally significant fractional flow reserve (≤ 0.80 cut-off point); contrast-flow quantitative flow ratio had a sensitivity of 85% (95% confidence interval 78% to 90%) and a specificity of 91% (95% confidence interval 85% to 95%). A total of 95% of quantitative flow ratio measurements were within 0.14 of the fractional flow reserve. Data on the diagnostic accuracy of CAAS vFFR were limited and a full meta-analysis was not feasible. There were very few data on clinical and implementation outcomes. The simulation found that quantitative flow ratio slightly increased the revascularisation rate when compared with fractional flow reserve, from 40.2% to 42.0%. Quantitative flow ratio and fractional flow reserve resulted in similar numbers of subsequent coronary events. The base-case cost-effectiveness results showed that the test strategy with the highest net benefit was invasive coronary angiography with confirmatory fractional flow reserve. The next best strategies were QAngio XA 3D/QFR and CAAS vFFR (without fractional flow reserve). However, the difference in net benefit between this best strategy and the next best was small, ranging from 0.007 to 0.012 quality-adjusted life-years (or equivalently £140-240) per patient diagnosed at a cost-effectiveness threshold of £20,000 per quality-adjusted life-year. Diagnostic accuracy evidence on CAAS vFFR, and evidence on the clinical impact of QAngio XA 3D/QFR, were limited. Quantitative flow ratio as measured by QAngio XA 3D/QFR has good agreement and diagnostic accuracy compared with fractional flow reserve and is preferable to standard invasive coronary angiography alone. It appears to have very similar cost-effectiveness to fractional flow reserve and, therefore, pending further evidence on general clinical benefits and specific subgroups, could be a reasonable alternative. The clinical effectiveness and cost-effectiveness of CAAS vFFR are uncertain. Randomised controlled trial evidence evaluating the effect of quantitative flow ratio on clinical and patient-centred outcomes is needed. Studies are required to assess the diagnostic accuracy and clinical feasibility of CAAS vFFR. Large ongoing randomised trials will hopefully inform the clinical value of QAngio XA 3D/QFR. This study is registered as PROSPERO CRD42019154575. This project was funded by the National Institute for Health Research (NIHR) Evidence Synthesis programme and will be published in full in Health Technology Assessment; Vol. 25, No. 56. See the NIHR Journals Library website for further project information.

Contrast FFR plus intracoronary injection of nitro-glycerine accurately predicts FFR for coronary stenosis functional assessment.

Fractional flow reserve (FFR) is the "gold standard" for assessing the physiological significance of coronary disease. In the last decade, several alternative adenosine-free indexes have been proposed in order to facilitate the dissemination of the functional evaluation of coronary stenosis. Our aim was to investigate whether radiographic contrast plus intracoronary nitroglycerin (cFFR-NTG) can predict functional assessment of coronary stenosis offering superior diagnostic agreement with FFR compared to non-hyperemic indexes and contrast mediated FFR (cFFR). Three hundred twenty-nine lesions evaluated with pressure wire in 266 patients were prospectively included in this multicenter study. The ROC curves for cFFR-NTG using an FFR≤0.80 showed a higher accuracy in predicting FFR (AUC=0.97) than resting Pd/Pa (AUC=0.90, P<0.01) and cFFR (AUC=0.93.5, P<0.01). A significant (P<0.01) strong correlation was found between FFR and the four analyzed indexes: Pd/Pa (r=0.78); iFR/RFR (r=0.73); cFFR(r=0.89) and cFFR-NTG (r=0.93). cFFR-NTG showed the closest agreement at Bland-Altman analysis. The cFFR-NTG cut off value >0.84 showed the highest negative predictive value (88%), specificity (91%), sensitivity (94%) and accuracy (92%) of the studied indexes. Submaximal hyperemic adenosine-free indexes are an efficient alternative to adenosine for the physiological assessment of epicardial coronary disease. The most accurate index in predicting the functional significance of coronary stenosis using FFR as reference was cFFR-NTG.

Effect of artery curvature on the coronary fractional flow reserve

Understanding the effect of the artery curvature on the pressure drop inside the arteries is of great importance due to the existence of several curved portions inside the coronary arterial system. In this paper, an experimental model is developed to account for the effect of the curvature of the coronary arteries on the pressure drop and Fractional Flow Reserve (FFR). FFR is an index for the evaluation of the functional significance of coronary stenosis and is defined as the ratio of the coronary pressure downstream of the stenosis to its upstream value. To measure the pressure drop and FFR across curved artery models, three-dimensional-printed curved artery models are fabricated and installed in the test section of the experimental rig. For ratios of curvature radius over the artery diameter ranging from 2 to 7, there are a minimum value for the pressure drop and, hence, a corresponding maximum value for FFR at a ratio of approximately 3. For the curved arteries with larger curvature radii, the pressure drop increases, and consequently, FFR decreases with an increase in the radius. The results showed that an accurate evaluation of the pressure drop and FFR inside a curved coronary artery can only be achieved by accounting for the effect of curvature parameters including the curvature angle and radius, such that neglecting the effect of the artery curvature results in an underestimation of the pressure drop by about 25%–35%. The developed equation is able to determine the pressure drop inside a curved coronary artery model noninvasively.

Adoption of Coronary Invasive Physiological Assessment in a Regional Tertiary Centre

Physiological assessment of coronary artery stenoses using fractional flow reserve (FFR) or instantaneous free wave pressure ratio (iFR) determines the functional significance of coronary stenoses to guide treatment. We aimed to describe the changing patterns and implications of use of these technologies.

Contrast FFR plus intracoronary injection of nitroglycerine accurately predicts FFR for coronary stenosis functional assessment

BACKGROUND Fractional flow reserve (FFR) is the gold standard for assessing the physiological significance of coronary disease. In the last decade, several alternative adenosine-free indexes have been proposed in order to facilitate the dissemination of the functional evaluation of coronary stenosis. Our aim was to investigate whether radiographic contrast plus intracoronary nitroglycerin (cFFR-NTG) can predict functional assessment of coronary stenosis offering superior diagnostic agreement with FFR compared to non-hyperemic indexes and contrast mediated FFR (cFFR). METHODS Three hundred twenty-nine lesions evaluated with pressure wire in 266 patients were prospectively included in this multicenter study. RESULTS The ROC curves for cFFR-NTG using an FFR≤0.80 showed a higher accuracy in predicting FFR (AUC=0.97) than resting Pd/Pa (AUC=0.90, P 0.84 showed the highest negative predictive value (88%), specificity (91%), sensitivity (94%) and accuracy (92%) of the studied indexes. CONCLUSIONS Submaximal hyperemic adenosine-free indexes are an efficient alternative to adenosine for the physiological assessment of epicardial coronary disease. The most accurate index in predicting the functional significance of coronary stenosis using FFR as reference was cFFR-NTG.

Meta-Analysis of Diagnostic Performance of Instantaneous Wave-Free Ratio versus Quantitative Flow Ratio for Detecting the Functional Significance of Coronary Stenosis.

Background Fractional flow reserve (FFR), as a functional measurement of coronary stenosis, is recommended for guiding revascularization in intermediate coronary lesions. However, it still remains underutilized for potential reasons including time consumption, costs, or contraindications associated with adenosine administration. Here we performed this meta-analysis to assess the diagnostic performance of two adenosine-free indices, instantaneous wave free-ratio (iFR), and quantitative flow ratio (QFR) in evaluating coronary stenosis severity with FFR as the reference standard. Methods PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched to include relevant studies with the diagnostic accuracy of iFR or QFR referenced to FFR. A bivariate model was applied to pool diagnostic parameters. We used Cochran's Q test and I2 index to assess heterogeneity and identify the potential source of heterogeneity by meta-regression. Results A total of 8213 lesions from 28 studies (19 for iFR and 9 for QFR) were included in this meta-analysis. The pooled sensitivity and specificity were 0.79 (95% CI, 0.75 to 0.83) and 0.85 (95% CI, 0.82 to 0.87) for iFR and 0.90 (95% CI, 0.84 to 0.93) and 0.88 (95% CI, 0.86 to 0.90) for QFR, respectively. Significantly higher sensitivity and specificity were observed in the bivariate analysis for QFR than for iFR (P < 0.001 for both). The area under summary receiver-operating curve of iFR and QFR was 0.89 (95% CI, 0.86 to 0.92) and 0.92 (95% CI, 0.89 to 0.94). Conclusion Evidence suggests that both of the two indices have good performance in detecting functional ischemia of coronary arteries and QFR might be a promising method without requiring the pressure wire. Further application of QFR may potentially provide important information to clinicians in the assessment of coronary lesions.

Информативность количественных показателей миокардиального кровотока и коронарного резерва по данным позитронно-эмиссионной томографии с 13N-аммонием, совмещенной с компьютерной томографией, в оценке функциональной значимости стенозов коронарных артерий

Информативность количественных показателей миокардиального кровотока и коронарного резерва по данным позитронно-эмиссионной томографии с 13N-аммонием, совмещенной с компьютерной томографией, в оценке функциональной значимости стенозов коронарных артерий

Diagnostic accuracy of a deep learning approach to calculate FFR from coronary CT angiography

BackgroundThe computational fluid dynamics (CFD) approach has been frequently applied to compute the fractional flow reserve (FFR) using computed tomography angiography (CTA). This technique is efficient. We developed the DEEPVESSEL-FFR platform using the emerging deep learning technique to calculate the FFR value out of CTA images in five minutes. This study is to evaluate the DEEPVESSEL-FFR platform using the emerging deep learning technique to calculate the FFR value from CTA images as an efficient method.MethodsA single-center, prospective study was conducted and 63 patients were enrolled for the evaluation of the diagnostic performance of DEEPVESSEL-FFR. Automatic quantification method for the three-dimensional coronary arterial geometry and the deep learning based prediction of FFR were developed to assess the ischemic risk of the stenotic coronary arteries. Diagnostic performance of the DEEPVESSEL-FFR was assessed by using wire-based FFR as reference standard. The primary evaluation factor was defined by using the area under receiver-operation characteristics curve (AUC) analysis.ResultsFor per-patient level, taking the cut-off value ≤ 0.8 referring to the FFR measurement, DEEPVESSEL-FFR presented higher diagnostic performance in determining ischemia-related lesions with area under the curve of 0.928 compare to CTA stenotic severity 0.664. DEEPVESSEL-FFR correlated with FFR (R = 0.686, P < 0.001), with a mean difference of –0.006 ± 0.0091 (P = 0.619). The secondary evaluation factors, indicating per vessel accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 87.3%, 97.14%, 75%, 82.93%, and 95.45%, respectively.ConclusionDEEPVESSEL-FFR is a novel method that allows efficient assessment of the functional significance of coronary stenosis.

Automatic coronary blood flow computation: validation in quantitative flow ratio from coronary angiography

To assess a novel approach for automatic flow velocity computation in deriving quantitative flow ratio (QFR) from coronary angiography. QFR is a novel approach for assessment of functional significance of coronary artery stenosis without using pressure wire and induced hyperemia. Patient-specific coronary flow is estimated semi-automatically by frame count method, which is subjective and inconvenient in the workflow of QFR analysis. The vascular structures were automatically delineated from coronary angiogram. Subsequently, the centerline of the interrogated vessel was extracted from the delineated lumen on each image frame and the change in the length of centerline was used to compute the flow velocity, which provided patient-specific flow for computation of QFR (QFRauto). A parameter derived from the increase in centerline length was used to automatically quantify the stability of contrast flow. From the two angiographic image runs used for three-dimensional angiographic reconstruction, the one with better stability was used to compute QFRauto. QFRauto was assessed in all patients enrolled in the FAVOR II China study, and compared with the commercialized QFR computational method based on frame count (QFRcount), using pressure wire-based fractional flow reserve (FFR) as the reference standard. Out of 328 vessels with paired FFR data, QFRauto was successfully computed on 325 (99%) vessels with acceptable stability in filling of contrast flow. The flow velocity computed by the proposed approach had a weak to moderate correlation with the frame count method (r = 0.37, p < 0.001), with mean differences of - 0.02 ± 0.07m/s (p < 0.001). QFRauto had good correlation (r = 0.96, p < 0.001) and agreement (mean difference: - 0.01 ± 0.04, p < 0.001) with QFRcount. Good correlation (r = 0.83, p < 0.001) and agreement (mean difference: 0.01 ± 0.06, p = 0.016) were also observed between QFRauto and FFR. Using FFR ≤ 0.80 to define functional significance of coronary stenosis, the overall diagnostic accuracy for QFRauto was 93.2% (95% CI 90.5-96.0%). The area under the receiver-operating characteristic curve did not differ significantly between QFRcount and QFRauto (difference: 0.00; 95% CI - 0.01 to 0.01; p = 0.529). Sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio for QFRauto were 92.4% (95% CI 86.0-96.5%), 93.7% (95% CI 89.5-96.6%), 14.7 (95% CI 8.7-25.0), and 0.1 (95% CI 0.0-0.2), respectively. Automatic computation of patient-specific coronary flow velocity based on coronary angiography is feasible. Assessment of QFR based on this novel approach had good diagnostic accuracy in determining the functional significance of coronary stenosis.