Invasive Fractional Flow Reserve Research Articles

Abstract 17031: Noninvasive CT-Based Hemodynamic Assessment Using 3D Printing and Virtual Functional Assessment Index

Background: Virtual functional assessment index (vFAI), an alternative approach for assessing hemodynamic significance of stenosis has been shown to enhance the diagnostic performance of coronary computed tomography angiography (CCTA) based on evaluating the area under pressure drop-flow curve for a stenosis. Previously, this was assessed via computational fluid dynamics. We investigated the evaluation of vFAI from CCTA images using 3D printing and an in vitro flow loop and its efficacy as compared to the invasively measured fractional flow reserve (FFR). Methods and Results: Eighteen patients with varying degrees of coronary artery disease who underwent non-invasive CCTA scans and invasive FFR of their left anterior descending coronary artery (LAD) were included. The LAD artery was segmented and reconstructed using Mimics (Materialise inc.,). The segmented models were then 3D printed using Carbon 3D printer (Carbon Inc.,) with rigid resins. An in vitro flow circulation system representative of invasive measurements in a cardiac catheterization laboratory was developed to experimentally evaluate the hemodynamic parameters of pressure and flow (Fig A). For each model, a range of physiological flow rates was applied by a peristaltic steady flow pump and titrated by a flow sensor. The pressure drop and the pressure ratio (Pd/Pa) were assessed for patient-specific aortic pressure and differing flow rates. vFAI was evaluated as the normalized area under the P d /P a vs Q curve from 0 to 240 mL/min. There was a strong correlation between vFAI and FFR, (R = 0.83, p < 0.001; Fig B) and a very good agreement between the two parameters by Bland-Altman analysis. The mean difference of measurements from the two methods was 0.06 (SD = 0.08, p=0.0063; Fig C), indicating a small systematic overestimation of the FFR by vFAI. Conclusions: vFAI can be effectively derived from 3D CTCA datasets using 3D-printed in vitro models, based on evaluation over a range of hemodynamic conditions.

Sex-specific risk for ischemia by invasive fractional flow reserve according to coronary atherosclerotic features: results from the CREDENCE trial

Abstract Background Evolving evidence suggests unique sex-specific mechanisms underlying coronary artery disease (CAD). However, it remains unknown if certain coronary atherosclerotic features confer a higher risk for ischemia in women versus men. Purpose To determine the association between coronary atherosclerotic features on coronary computed tomography angiography (CCTA) and ischemia by invasive fractional flow reserve (FFR) in women versus men. Methods Secondary analysis of the CREDENCE trial, including patients referred for nonemergent invasive coronary angiography (ICA). All patients underwent CCTA with semi-automatic quantification of coronary atherosclerosis, as well as ICA with FFR interrogation of all major epicardial arteries ≥2 mm. Generalized estimating equations were calculated to assess the association between coronary atherosclerotic features and invasive vessel-specific ischemia (FFR ≤0.80). Sex interactions were tested, adjusted for age. Results From 612 patients (mean age 64±10 years, 30% women) with 1,686 analyzed vessels, a total of 436 (26%) vessels were ischemic. Women were significantly older than men (p<0.001), but with similar distribution of risk factors and medication usage (p≥0.09). In both women and men, all general and compositional features of coronary atherosclerosis were significantly associated with ischemia. However, tests for interaction (Figure 1) revealed higher relative odds for ischemia among women as compared to men for total percent atheroma volume ([PAV], p=0.006), the number of lesions with high-risk plaque (p=0.027), the number of lesions with >30% stenosis (p=0.030), noncalcified PAV <130 HU and <350 HU (p≤0.003), and calcified PAV (p=0.007). Conclusion Our results support a prominent influence of coronary atherosclerotic features that uniquely impact ischemic risk among women more so than men. These data support the role of CCTA for providing valuable information to guide management of symptomatic women. Figure 1. Ischemic risk in women vs. men Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Institutes of Health - National Heart, Lung, and Blood Institute

Effect of plaque characteristics on ischemia by invasive fractional flow reserve in nonobstructive versus obstructive coronary artery disease: results from the CREDENCE trial

Abstract Background Mismatches between the severity of coronary stenosis and the presence of ischemia by invasive fractional flow reserve (FFR) are frequently reported. Purpose To investigate whether plaque characteristics as evaluated with coronary computed tomography angiography (CCTA) may explain this discordance in nonobstructive versus obstructive coronary artery disease (CAD). Methods From the CREDENCE trial, 612 patients with suspected CAD at 13 sites (64±10 years, 70% men) underwent CCTA with semi-automated whole heart quantification and invasive coronary angiography with 3-vessel FFR measurements. Obstructive CAD was visually defined as ≥50% stenosis. The primary endpoint of coronary vessel-specific ischemia was defined as FFR ≤0.80. Generalized estimating equations were calculated to evaluate the effect of plaque characteristics on coronary vessel-specific ischemia. Interactions were tested by obstructive CAD, adjusted for age. Results Among 1,686 vessels, ischemia was present in 436 (26%) vessels. In both nonobstructive and obstructive CAD, the majority of plaque characteristics were associated with coronary vessel-specific ischemia (p≤0.005, Figure 1). In nonobstructive CAD, odds for ischemia were significantly higher for total percent atheroma volume (PAV, p<0.001), calcified PAV (p<0.001), noncalcified PAV <350 and <130 HU (p≤0.043), the number of lesions at a bifurcation (p=0.009) and the number of lesions with high-risk plaque (HRP, p=0.033) when compared with obstructive CAD. Conclusion Our findings reveal that ischemia by FFR is documented in the setting of both nonobstructive and obstructive CAD on CCTA. Detection of atherosclerotic plaque characteristics associated with ischemia can potentially improve diagnostic certainty and guide management of symptomatic patients with nonobstructive CAD. Figure 1. Odds ratios for ischemia. Funding Acknowledgement Type of funding source: Public grant(s) – National budget only. Main funding source(s): National Institutes of Health - National Heart, Lung, and Blood Institute

A cost effectiveness study into the detection of functionally significant coronary artery disease in patients with chronic coronary syndrome: a decision-analytic modelling approach

Abstract Background ESC guidelines recommend functional or anatomical imaging for stable coronary artery disease (CAD) diagnosis. We investigated cost-effective diagnostic strategies for CAD detection with invasive coronary angiography (ICA) and fractional flow reserve (FFR) as reference standard [1,2], using NHS reference costs. Methods Deterministic and probabilistic decision-analytic models for diagnostic strategies in low (25%), intermediate (50%) and high (75%) risk CAD were devised. Strategies: standalone or combined testing with computed tomographic coronary angiography (CTCA), stress echocardiography (SE), CT-FFR, single-photon emission computed tomography (SPECT), cardiac magnetic resonance (CMR), positron emission tomography (PET), ICA, and ICA-FFR. Proportion of correct diagnosis served as measure of clinical effectiveness. Incremental cost-effectiveness ratios were calculated for dominant strategies. Cost-effectiveness acceptability curves (CEAC) tested variation of cost-effectiveness threshold (CET). Results Base case (Table 1) consistent with probabilistic analysis (Figure 1 left). CEACs (Figure 1 right). Conclusions Direct ICA is not cost-effective. Functional testing has significant role in low/intermediate risk. CMR is cost-effective in all risk and most likely cost-effective in CETs <£10,000. ICA-FFR yields highest correct diagnoses in all at highest cost. Future long-term follow-up studies with quality of life measures are needed.

The imortance of hyperemic contrast velocity assessment on image-based fractional flow reserve calculation

Abstract Aims Image-based fractional flow reserve (FFR) calculations reported good agreement with FFR measured invasively. The purpose of this study was to perform a retrospective analysis of the cases of a previous study on less invasive FFR calculation (simple FFR: FFRsim) as a simple calculation from hyperemic contrast flow data and three-dimensional coronary parameters. Methods and results We aimed to analyze the relations between the pressure wire-based FFR (FFRmeas) and fixed FFRsim: calculated from the fixed hyperemic velocity, rest FFRsim: calculated using the non-hyperemic frame count data to extrapolate the hyperemic velocity (based on the database used in the FAVOR1 study) hyp FFRsim: the hyperemic velocity derived from the frame count assessment during vasodilation.To calculate the frame count reserve (CFRFC) the resting frame count was divided by the hyperemic frame count; this value was then used to determine the CFRFC/FFRmeas ratio as an indicator of microvascular function in the corresponding myocardial area of the measured coronary vessel. A total of 50 lesions with intermediate stenosis were investigated. Correlation between rest FFRsim (from the resting frame count extrapolated to the hyperemic velocity) and FFRmeas was lower than the correlation between hyp FFRsim and FFRmeas (r=0.761 vs. 0.824). Based on ROC curve analysis for predicting the abnormal FFR of ≤0.80 the AUC were significantly higher for the hyperemia-based parameter than those calculated from resting frame counts. Significantly higher AUC were detected by the hyp FFRsim than by the rest FFRsim: 0.936 (95% CI: 0.828 to 0.985) vs. 0.862 (CI: 0.734 to 0.943); p=0.011. Linear regression analyses between the FFRsim (either by fixed FFRsim or by rest FFRsim or by hyp FFRsim methods) and the FFRmeas showed higher intercepts and less steep of the slopes in the subgroups with presence of microvascular disease defined as CFRFC/FFRmeas <2 than in those without microvascular disease (CFRFC/FFRmeas >2); the difference reached significant level (p=0.019) when calculated by rest FFRsim. Conclusions Hyperemic challenge either by adenosine or regadenoson is required for exact image-based FFR calculation especially in cases of suspicion for microvascular coronary disease. Funding Acknowledgement Type of funding source: None

Umbrella review and multivariate meta-analysis of diagnostic test accuracy studies on hybrid non-invasive imaging for coronary artery disease

BackgroundThe diagnosis of coronary artery disease (CAD) remains challenging. It is uncertain whether hybrid imaging can improve diagnostic accuracy for CAD. MethodsThis is a systematic review and multivariate meta-analysis. We searched PubMed and The Cochrane Library for recent (≥ 2010) systematic reviews of diagnostic test accuracy studies on non-invasive imaging for CAD. Study-level data were extracted from them, and pooled with pairwise and multivariate meta-analytic methods, using invasive coronary angiography (ICA) or invasive fractional flow reserve (FFR) as reference standards, focusing on sensitivity and specificity. ResultsDetails from 661 original studies (71,823 patients) were pooled. Pairwise meta-analysis using ICA as reference showed that anatomic imaging was associated with the best diagnostic accuracy (sensitivity = 0.95 [95% confidence interval 0.94-0.96], specificity = 0.83 [0.81-0.85]), whereas using FFR as reference identified hybrid imaging as the best test (sensitivity = 0.87 [0.83-0.90], specificity = 0.82 [0.76-0.87]). Multivariate meta-analysis confirmed the superiority of anatomic imaging using ICA as reference (sensitivity = 0.96, specificity = 0.83), and hybrid imaging using FFR as reference (sensitivity = 0.88 [0.86-0.91], specificity = 0.82 [0.77-0.87]). ConclusionsNon-invasive hybrid imaging tests appear superior to anatomic or functional only tests to diagnose ischemia-provoking coronary lesions, whereas anatomic imaging is best to diagnose and/or rule out angiographically significant CAD. Systematic review registrationPROSPERO Registry Number CRD42018088528.

Fractional flow reserve derived from coronary computed tomography: where are we now and where are we heading?

Computed tomography coronary angiography is emerging as the preferred diagnostic tool for patients with chest pain. Additional knowledge of the extent and distribution of myocardial ischemia enables tailored patient management. Computed tomography-derived fractional flow reserve (FFRCT) employs computed tomography coronary angiography raw data processed via complex computational fluid dynamics and produces a surrogate of the invasive fractional flow reserve (FFR) thus delivering anatomical and physiological assessment in a single test. FFRCT has been extensively validated against invasive FFR and observational clinical studies have consistently demonstrated its utility as gatekeeper to invasive angiography while also reducing downstream clinical events and costs. Novel workstation-based models of estimating FFR are now being tested. Ongoing and future research results will define their role in clinical practice.

Review: FFRCT Changing the Face of Cardiac CT

Non-invasive fractional flow reserve derived from CT coronary angiography (FFRCT) offers an amalgamation of both coronary anatomy and physiology. This review aims to provide a contemporary evaluation of the evidence for clinical use of FFRCT. The review article pays particular attention to the importance of patient preparation, anatomical features, scan quality and the overall interpretation of results that can lead to the best use of FFRCT analysis. Previous cost evaluations of the technology are compared and reviewed. Diagnostic accuracy of FFRCT in comparison with CTA has been established in several clinical studies previously. More recent studies for FFRCT use have focused on the clinical utility of the technology, in comparison with other non-invasive testing for coronary artery disease and the prognostic data of FFRCT. The registry data has demonstrated FFRCT as a comparable indicator of cardiac prognosis to invasive fractional flow reserve. Future research areas include the use of FFRCT to plan coronary revascularisation prior to procedures and even perhaps to predict future cardiac event using computational flow dynamic data. FFRCT is now an established technology for the diagnosis of coronary artery disease with increasing use in clinical practice. The potential of the technology to deliver cost savings, improved triage and more directed management will depend upon the manner of its use. Future applications of the principles of FFRCT have broad potential for improved understanding of coronary artery disease and superior management of patients afflicted with it.

Determination of the Optimal Measurement Point for Fractional Flow Reserve Derived From CTA Using Pressure Wire Assessment as Reference.

BACKGROUND. For clinical decision making, it was recently recommended that values of fractional flow reserve (FFR) derived from coronary CTA (FFRCT) be measured 1-2 cm distal to the stenosis, given the potential for overestimation of ischemia when FFRCT values at far distal segments are used. Supporting data are, however, lacking. OBJECTIVE. The purpose of the present study was to evaluate the diagnostic performance of FFRCT values measured 1-2 cm distal to the stenosis and at more distal locations relative to invasive FFR values. METHODS. FFRCT and invasive FFR values for 365 vessels in 253 patients identified from the Assessing Diagnostic Value of Noninvasive FFRCT in Coronary Care (ADVANCE) registry were prospectively assessed. FFRCT values were measured 1-2 cm distal to the stenosis and at the pressure wire position and far distal segments. The diagnostic accuracy of FFRCT was assessed on the basis of the ROC AUC. The AUC of FFRCT was calculated using FFRCT as an explanatory variable and an invasive FFR of 0.80 or less as the dichotomous dependent variable. RESULTS. The AUC of FFRCT values measured 1-2 cm distal to the stenosis (0.85; 95% CI, 0.80-0.88) was higher (p = .002) than that of FFRCT values measured at far distal segments (0.80; 95% CI, 0.76-0.84) and similar (p = .16) to that of FFRCT values measured at the pressure wire position (0.86; 95% CI, 0.81-0.89). FFRCT values measured 1-2 cm distal to the stenosis and at far distal segments had sensitivity of 87% versus 92% (p = .003), specificity of 73% versus 42% (p < .001), PPV of 75% versus 59% (p < .001), and NPV of 86% versus 85% (p = .72), respectively. Subgroup analyses of lesions of the left anterior descending coronary artery, left circumflex coronary artery, and right coronary artery all showed improved specificity and PPV (all p < .005) for FFRCT values measured 1-2 cm distal to the stenosis compared with values measured at the pressure wire position. However, the AUC was higher for measurements obtained 1-2 cm distal to the stenosis versus those obtained at far distal segments, for left anterior descending coronary artery lesions (p < .001) but not for left circumflex coronary artery lesions (p = .27) or right coronary artery lesions (p = .91). CONCLUSION. The diagnostic performance of FFRCT values measured 1-2 cm distal to the stenosis was higher than that of FFRCT values measured at far distal segments and was similar to that of FFRCT values measured at the pressure wire position in evaluating ischemic status, particularly for left anterior descending coronary artery lesions. CLINICAL IMPACT. The present study supports recent recommendations from experts to use FFRCT measured 1-2 cm distal to the stenosis, rather than measurements obtained at far distal segments, in clinical decision making.

Stress Myocardial Perfusion Imaging vs Coronary Computed Tomographic Angiography for Diagnosis of Invasive Vessel-Specific Coronary Physiology

Stress imaging has been the standard for diagnosing functionally significant coronary artery disease. It is unknown whether novel, atherosclerotic plaque measures improve accuracy beyond coronary stenosis for diagnosing invasive fractional flow reserve (FFR) measurement. To compare the diagnostic accuracy of comprehensive anatomic (obstructive and nonobstructive atherosclerotic plaque) vs functional imaging measures for estimating vessel-specific FFR. Controlled clinical trial of diagnostic accuracy with a multicenter derivation-validation cohort of patients referred for nonemergent invasive coronary angiography. A total of 612 patients (64 [10] years; 30% women) with signs and symptoms suggestive of myocardial ischemia from 23 sites were included. Patients were recruited from 2014 to 2017. Data analysis began in August 2018. Patients underwent invasive coronary angiography with measurement of invasive FFR, coronary computed tomographic angiography (CCTA) quantification of atherosclerotic plaque and FFR by CT (FFR-CT), and semiquantitative scoring of rest/stress myocardial perfusion imaging (by magnetic resonance, positron emission tomography, or single photon emission CT). Multivariable generalized linear mixed models were derived and validated calculating the area under the receiver operating characteristics curve. The primary end point was invasive FFR of 0.80 or less. Of the 612 patients, the mean (SD) age was 64 (10) years, and 426 (69.9%) were men. An invasive FFR of 0.80 or less was measured in 26.5% of 1727 vessels. In the derivation cohort, CCTA vessel-specific factors associated with FFR 0.80 or less were stenosis severity, percentage of noncalcified atheroma volume, lumen volume, the number of lesions with high-risk plaque (≥2 of low attenuation plaque, positive remodeling, napkin ring sign, or spotty calcification), and the number of lesions with stenosis greater than 30%. Fractional flow reserve-CT was not additive to this model including stenosis and atherosclerotic plaque. Significant myocardial perfusion imaging predictors were the summed rest and difference scores. In the validation cohort, the areas under the receiver operating characteristic curve were 0.81 for CCTA vs 0.67 for myocardial perfusion imaging (P < .001). A comprehensive anatomic interpretation with CCTA, including quantification of obstructive and nonobstructive atherosclerotic plaque, was superior to functional imaging in the diagnosis of invasive FFR. Comprehensive CCTA measures improve prediction of vessel-specific coronary physiology more so than stress-induced alterations in myocardial perfusion. ClinicalTrials.gov Identifier: NCT02173275.

Low-dose CT perfusion with combined use of CTP and CTP-derived coronary CT angiography at 70kVp: validation with invasive fractional flow reserve.

To investigate the diagnostic performance of 70-kVp stress dynamic myocardial CT perfusion (CTP) as a low-dose, one-stop cardiac CT examination in clinical application. Consecutive symptomatic patients were prospectively recruited and scanned with stress dynamic myocardial CTP. The CTP phase with the best enhancement of the coronary arteries was selected and extracted as the CTP-derived single-phase coronary CT angiography (SP-CTA). The diagnostic performance of CTP and CTP+SP-CTA for functionally significant CAD was assessed. Invasive coronary angiography and fractional flow reserve were used as the reference standard for the myocardial ischemia evaluation. In total, 71 patients (43 men and 28 women; 63.6 ± 8.8years old) underwent the stress dynamic myocardial CTP; 63 vessels (36.2%) from 42 of the patients (59.2%) were identified as causing ischemia. On a per-vessel basis, the sensitivity, specificity, PPV, NPV, and diagnostic accuracy for CTP and CTP+SP-CTA were 77.8%, 93.7%, 87.5%, 88.1%, and 87.9% and 84.1%, 93.7%, 88.3%, 91.2%, and 90.2%, respectively. The area under the curve (AUC) of CTP+SP-CTA (AUC = 0.963; 95%CI, 0.938-0.989) was significantly superior to that of CTP (AUC = 0.922; 95%CI, 0.880-0.964) and that of SP-CTA (AUC = 0.833; 95%CI, 0.765-0.900) alone (all p < 0.01). The mean radiation dose of the CTP examination was 3.8 ± 1.4mSv. CTP-derived SP-CTA improved the diagnostic value of CTP. With a promising performance of myocardial ischemia detection and low radiation dose, the innovative low-dose, one-stop CTP examination is clinically feasible for patients who need to receive a myocardial perfusion assessment. • Myocardial CTP performed well in the evaluation of hemodynamically significant CAD. • CTP-derived single-phase CCTA improved the diagnostic value of CTP. • The combined use of low-dose CTP and CTP-derived CCTA at 70kVp is clinically feasible for CAD patients who need to receive a myocardial perfusion assessment.

Diagnostic performance of quantitative, semi-quantitative, and visual analysis of dynamic CT myocardial perfusion imaging: a validation study with invasive fractional flow reserve.

To investigate the diagnostic performance of absolute myocardial blood flow (MBF), MBFratio, and visual analysis of dynamic CT myocardial perfusion imaging (CT-MPI) for the detection of hemodynamically significant coronary stenosis. Consecutive patients with chest pain and intermediate-to-high pre-test probability of obstructive coronary artery disease were prospectively enrolled. All patients were referred for dynamic CT-MPI and fractional flow reserve (FFR) measurements within 4weeks. Absolute MBF, MBFratio (mean MBF of stenosis-subtended territories versus that of reference territories), and visually identified perfusion defect were tested for the diagnostic performance with reference to FFR. Sixty-two patients with 95 target vessels were included for final analysis. The mean radiation dose for dynamic CT-MPI was 3.0 (2.2-4.0) mSv. The mean lesion-based absolute MBF value was significantly lower in ischemic segments than that in non-ischemic segments (78.0 (65.0-86.0) mL/min/100mL vs. 133.0 (117.5-163.8) mL/min/100mL, p < 0.001). Similarly, the lesion-based MBFratio was also markedly lower in territories with positive FFR results (0.52 (0.44-0.64) vs. 0.93 (0.91-0.97), p < 0.001). According to per-lesion ROC curve analysis, MBF and MBFratio had a similar area under the curve (AUC) for detecting hemodynamically significant lesions (AUC = 0.942 vs. 0.956, p = 0.413), which were larger than that of visual analysis (AUC = 0.802, both p < 0.01). The vessel-based sensitivity, specificity, and diagnostic accuracy were 84.3%, 97.7%, and 90.5% for MBF and 96.1%, 93.2%, and 94.7% for MBFratio. Absolute MBF and MBFratio had similarly excellent diagnostic performance with reference to FFR. In addition, these two parameters outperformed visual analysis for the detection of myocardial ischemia. • The mean MBF and MBFratio were significantly lower in ischemic segments than those in non-ischemic segments. • Absolute MBF and MBFratio had similar AUCs for the detection of hemodynamically significant lesions (AUC = 0.942 vs. 0.956, p = 0.413), which were larger than that of visual analysis (AUC = 0.802, both p < 0.01). • The vessel-based sensitivity, specificity, and diagnostic accuracy were 84.3%, 97.7%, and 90.5% for absolute MBF and 96.1%, 93.2%, and 94.7% for MBFratio.

Artificial intelligence approaches to predict coronary stenosis severity using non-invasive fractional flow reserve

Fractional flow reserve is the current reference standard in the assessment of the functional impact of a stenosis in coronary heart disease. In this study, three models of artificial intelligence of varying degrees of complexity were compared to fractional flow reserve measurements. The three models are the multivariate polynomial regression, which is a statistical method used primarily for correlation; the feed-forward neural network; and the long short-term memory, which is a type of recurrent neural network that is suited to modelling sequences. The models were initially trained using a virtual patient database that was generated from a validated one-dimensional physics-based model. The feed-forward neural network performed the best for all test cases considered, which were a single vessel case from a virtual patient database, a multi-vessel network from a virtual patient database, and 25 clinically invasive fractional flow reserve measurements from real patients. The feed-forward neural network model achieved around 99% diagnostic accuracy in both tests involving virtual patients, and a respectable 72% diagnostic accuracy when compared to the invasive fractional flow reserve measurements. The multivariate polynomial regression model performed well in the single vessel case, but struggled on network cases as the variation of input features was much larger. The long short-term memory performed well for the single vessel cases, but tended to have a bias towards a positive fractional flow reserve prediction for the virtual multi-vessel case, and for the patient cases. Overall, the feed-forward neural network shows promise in successfully predicting fractional flow reserve in real patients, and could be a viable option if trained using a large enough data set of real patients.

The transluminal attenuation gradient does not add diagnostic accuracy to coronary computed tomography.

A method for improving the accuracy of coronary computed tomography angiography (CCTA) is highly sought after as it would help to avoid unnecessary invasive coronary angiographies. Measurement of the transluminal attenuation gradient (TAG) has been proposed as an alternative to other existing methods, i.e. CT perfusion and CT fractional flow reserve (FFR). To evaluate the incremental value of three types of TAG in high-pitch spiral CCTA with invasive FFR measurements as reference. TAG was measured using two semi-automatic methods and one manual method. A receiver operating characteristic (ROC) analysis was made to determine the usefulness of TAG alone as well as TAG combined with CCTA for detection of significant coronary artery stenoses defined by an invasive FFR value ≤0.80. A total of 51 coronary vessels in 37 patients were included in this retrospective study. Hemodynamically significant stenoses were found in 13 vessels according to FFR. The ROC analysis TAG alone resulted in areas under the curve (AUCs) of 0.530 and 0.520 for the semi-automatic TAG and 0.557 for the manual TAG. TAG and CCTA combined resulted in AUCs of 0.567, 0.562 for semi-automatic TAG, and 0.569 for the manual TAG. The results from our study showed no incremental value of TAG measured in single heartbeat CCTA in determining the severity of coronary artery stenosis degrees.

Diagnostic accuracy of two-dimensional coronary angiographic-derived fractional flow reserve-Preliminary results.

Noninvasive fractional flow reserve (NiFFR) is an emerging method for evaluating the functional significance of a coronary lesion during diagnostic coronary angiography (CAG). The method relies on the computational flow dynamics and the three-dimensional (3D) reconstruction of the vessel extracted from CAG. In the present study, we sought to evaluate the diagnostic performance and applicability of 2D-based NiFFR. In this prospective observational study, we evaluated 2D-based NiFFR in 279 candidates for invasive CAG and invasive fractional flow reserve (FFR). NiFFR was calculated via two methods: variable NiFFR, in which the contrast transport time was extracted from the angiographic view, and fixed NiFFR, in which a prespecified frame count was applied. The final analysis was performed on 245 patients (250 lesions). Variable NiFFR had an area under the receiver operating characteristic curve of 81.5%, an accuracy of 80.0%, a sensitivity of 82.2%, a specificity of 82.2%, a negative predictive value of 91.4%, and a positive predictive value of 63.6%. The mean difference between FFR and NiFFR was -0.0244 ±.0616 (p ≤.0001). A pressure wire-free hybrid strategy was possible in 68.8% of our population with variable NiFFR. Our 2D-based NiFFR yielded results comparable to those derived from 3D-based software. Our findings should; however, be confirmed in larger trials.

Computed Tomography Coronary Plaque Characteristics Predict Ischemia Detected by Invasive Fractional Flow Reserve.

Coronary computed tomography angiography (CCTA) plaque quantification has been proposed to be of incremental value in the prediction of ischemia, although prior studies have shown conflicting results. We aimed to determine whether CCTA plaque features assessed on a commercial vendor platform predict invasive fractional flow reserve (FFR)/instantaneous wave-free ratio (IFR). Consecutive patients who underwent CCTA for evaluation of suspected stable coronary artery disease followed by invasive coronary physiology testing within 60 days at a single academic center were identified retrospectively. Semiautomated plaque quantification of the vessel proximal to the location of FFR/IFR measurement was carried out in TeraRecon, along with simple visual assessment for high-risk plaque features of positive remodeling, spotty calcification, low-attenuation plaque (LAP), and lesion length. Ischemia was defined by FFR ≤0.80 or IFR ≤0.89. A total of 134 patients (62% male, mean age 62±10 y) were included in this study. On univariate logistic regression, the following visual plaque analysis parameters were predictive of ischemia: positive remodeling (odds ratio [OR] with 95% confidence interval [CI]: 4.96; 2.25-10.95; P<0.001), lesion length (OR for every 1 mm with 95% CI: 1.24; 1.14-1.34; P<0.001), spotty calcification (OR with 95% CI: 6.67; 1.67-26.64; P=0.007), and LAP (OR with 95% CI: 30; 3.78-246; P=0.001). None of the semiautomated plaque quantification parameters, such as noncalcified plaque volume or LAP volume, were predictive of ischemia. On stepwise multivariable logistic regression, lesion length (OR with 95% CI: 1.25; 1.14-1.37; P<0.0001) and LAP (OR with 95% CI: 43; 4.4-438; P=0.001) were significant predictors of ischemia, improving the area under the curve of CCTA from 0.53 to 0.87. Simple visual plaque assessment for high-risk plaque features improved the performance of CCTA to predict ischemia. Semiautomated plaque quantification performed on a commercial vendor platform was not predictive of ischemia.

Validation of the diagnostic performance of ‘HeartMedi V.1.0’, a novel CT-derived fractional flow reserve measurement, for patients with coronary artery disease: a study protocol

IntroductionCoronary CT angiography (CCTA) is widely used for non-invasive coronary artery evaluation, but it is limited in identifying the nature of functional characteristics that cause ischaemia. Recent computational fluid dynamic...

CT Coronary Plaque Characteristics Predict Ischemia Detected By Invasive Fractional Flow Reserve.

CT Coronary Plaque Characteristics Predict Ischemia Detected By Invasive Fractional Flow Reserve.

Novel radiomics features from CCTA images for the functional evaluation of significant ischaemic lesions based on the coronary fractional flow reserve score

To explore the superiority of radiomics analysis in the diagnostic performance of coronary computed tomography angiography (CCTA) for identifying myocardial ischaemia and predicting major adverse cardiovascular events (MACE). A total of 105 lesions from 88 patients who underwent CCTA and invasive fractional flow reserve measurement were collected as the training set, and another 31 patients with CCTA and clinical outcome information were used as the validation set. Conventional CCTA features included the stenosis diameter, length, Agatston score and high-risk plaque characteristics. After extracting and selecting radiomics features, the robustness of the radiomics features was examined, and then conventional and radiomics models were established using logistic regressions. The area under the receiver operating characteristic (ROC) curve (AUC) and Net Reclassification Index (NRI) were analysed to compare the discrimination and classification abilities between the two models in both the training and validation sets. A total of 1409 radiomics features were extracted, and three wavelet features were finally screened out. The robustness test showed good stability for the refined radiomics features. Compared with the conventional model, the radiomics model displayed a significantly improved diagnostic performance in the training set (AUC 0.762 vs. 0.631, 95% confidence interval [CI] 0.671-0.853 vs. 0.519-0.742, P = 0.058) but a slightly improved diagnostic performance in the validation set (AUC 0.671 vs. 0.592, 95% CI 0.466-0.875 vs. 0.519-0.742, P = 0.448). The NRI of the radiomics model was increased in both the training and validation sets (NRI 0.198 and 0.238, respectively). Quantitative radiomics analysis was feasible and might help to improve the diagnostic performance of CCTA but is still controversial for predicting MACE.

Coronary computed tomography angiography derived flow fractional reserve: the state of the art

Coronary computed tomographic angiography (CCTA) is an effective examination with high sensitivity to rule out obstructive coronary artery disease (CAD). It can provide anatomical information of coronary artery disease, such as the degree of stenosis, plaque characteristics, but has poor discriminatory power for hemodynamically significant lesions, which may lead to unnecessary referrals for invasive coronary angiography (ICA). Invasive fractional flow reserve (FFR) is generally considered as the gold standard for the functional evaluation of CAD. However, high cost and invasive characteristics of FFR limit its wide clinical application. Recently, non-invasive CT-derived fractional flow reserve (CT-FFR), a novel image post-processing technique combining the advantages of CCTA and FFR, allows us to obtain both anatomic and functional information of a coronary lesion. CT-FFR has been used in diagnosing and guiding clinical management of CAD patients. This review introduces the basic principles, key points of CT-FFR analysis, and current research progress of CT-FFR.