Accuracy of computational pressure-fluid dynamics applied to coronary angiography to derive fractional flow reserve: FLASH FFR

Establishing the longitudinal hemodynamic mapping framework for wearable-driven coronary digital twins

Understanding the evolving nature of coronary hemodynamics is crucial for early disease detection and monitoring progression. We require digital twins that mimic a patient's circulatory system by integrating continuous physiological data and computing hemodynamic patterns over months. Current models match clinical flow measurements but are limited to single heartbeats. To this end, we introduced the longitudinal hemodynamic mapping framework (LHMF), designed to tackle critical challenges: (1) computational intractability of explicit methods; (2) boundary conditions reflecting varying activity states; and (3) accessible computing resources for clinical translation. We show negligible error (0.0002-0.004%) between LHMF and explicit data of 750 heartbeats. We deployed LHMF across traditional and cloud-based platforms, demonstrating high-throughput simulations on heterogeneous systems. Additionally, we established LHMFC, where hemodynamically similar heartbeats are clustered to avoid redundant simulations, accurately reconstructing longitudinal hemodynamic maps (LHMs). This study captured 3D hemodynamics over 4.5 million heartbeats, paving the way for cardiovascular digital twins.

Effective descriptor extraction strategies for correspondence matching in coronary angiography images

The importance of 3D reconstruction of coronary arteries using multiple coronary angiography (CAG) images has been increasingly recognized in the field of cardiovascular disease management. This process relies on the camera matrix's optimization, needing correspondence info for identical point positions across two images. Therefore, an automatic method for determining correspondence between two CAG images is highly desirable. Despite this need, there is a paucity of research focusing on image matching in the CAG images. Additionally, standard deep learning image matching techniques often degrade due to unique features and noise in CAG images. This study aims to fill this gap by applying a deep learning-based image matching method specifically tailored for the CAG images. We have improved the structure of our point detector and redesigned loss function to better handle sparse labeling and indistinct local features specific to CAG images. Our method include changes to training loss and introduction of a multi-head descriptor structure leading to an approximate 6% improvement. We anticipate that our work will provide valuable insights into adapting techniques from general domains to more specialized ones like medical imaging and serve as an improved benchmark for future endeavors in X-ray image-based correspondence matching.

Advancements and future perspectives in coronary angiography-derived fractional flow reserve

Angiography-derived fractional flow reserve (FFR) has emerged as a non-invasive technique to assess the functional significance of coronary artery stenoses. The clinical applications of angiography-derived FFR span a wide range of scenarios, including assessing intermediate coronary lesions and guiding revascularization decisions. This review paper aims to provide an overview of angiography-derived FFR, including its principles, clinical applications, and evidence supporting its accuracy and utility. Lastly, the review discusses future directions and ongoing research in the field, including the integration of angiography-derived FFR into routine clinical practice.

Future of invasive and non-invasive hemodynamic assessment for coronary artery disease management

Coronary artery disease represents a global health challenge. Accurate diagnosis and evaluation of hemodynamic parameters are crucial for optimizing patient management and outcomes. Nowadays a wide range of both non-invasive and invasive methods are available to assess the hemodynamic impact of both epicardial coronary stenosis and vasomotor disorders. In fact, over the years, important developments have reshaped the nature of both invasive and non-invasive diagnostic techniques, and the future holds promises for further innovation and integration. Non-invasive techniques have progressively evolved and currently a broad spectrum of methods are available, from cardiac magnetic resonance imaging with pharmacological stress and coronary computed tomography (CT) to the newer application of FFR-CT and perfusion CT. Invasive methods, on the contrary, have developed to a full-physiology approach, able not only to identify functionally significant lesions but also to evaluate microcirculation and vasospastic disease. The aim of this review is to summarize the current state-of-the-art of invasive and non-invasive hemodynamic assessment for CAD management.

Diagnostic Performance of Coronary Angiography Derived Computational Fractional Flow Reserve

BACKGROUND

Computational fluid dynamics can compute fractional flow reserve (FFR) accurately. However, existing models are limited by either the intravascular hemodynamic phenomarkers that can be captured or the fidelity of geometries that can be modeled.

METHODS AND RESULTS

This study aimed to validate a new coronary angiography-based FFR framework, FFRHARVEY, and examine intravascular hemodynamics to identify new biomarkers that could augment FFR in discerning unrevascularized patients requiring intervention. A 2-center cohort was used to examine diagnostic performance of FFRHARVEY compared with reference wire-based FFR (FFRINVASIVE). Additional biomarkers, longitudinal vorticity, velocity, and wall shear stress, were evaluated for their ability to augment FFR and indicate major adverse cardiac events. A total of 160 patients with 166 lesions were investigated. FFRHARVEY was compared with FFRINVASIVE by investigators blinded to the invasive FFR results with a per-stenosis area under the curve of 0.91, positive predictive value of 90.2%, negative predictive value of 89.6%, sensitivity of 79.3%, and specificity of 95.4%. The percentage ofdiscrepancy for continuous values of FFR was 6.63%. We identified a hemodynamic phenomarker, longitudinal vorticity, as a metric indicative of major adverse cardiac events in unrevascularized gray-zone cases.

CONCLUSIONS

FFRHARVEY had high performance (area under the curve: 0.91, positive predictive value: 90.2%, negative predictive value: 89.6%) compared with FFRINVASIVE. The proposed framework provides a robust and accurate way to compute a complete set of intravascular phenomarkers, in which longitudinal vorticity was specifically shown to differentiate vessels predisposed to major adverse cardiac events.

Prognostic Value of Coronary Microvascular Dysfunction Assessed by Coronary Angiography-Derived Index of Microcirculatory Resistance in Patients With ST-Segment Elevation Myocardial Infarction

BACKGROUND

CaIMR is proposed as a novel angiographic index designed to assess microcirculation without the need for pressure wires or hyperemic agents. We aimed to investigate the impact of caIMR on predicting clinical outcomes in STEMI patients.

METHODS

One hundred and forty patients with STEMI who received PCI in Putuo Hospital of Shanghai from October 2021 to September 2022 were categorized into CMD and non-CMD groups according to the caIMR value. The baseline information, patient-related examinations, and the occurrence of MACE at the 12-month follow-up were collected to investigate risk factors in patients with STEMI.

RESULTS

We divided 140 patients with STEMI enrolled into two groups according to caIMR results, including 61 patients diagnosed with CMD and 79 patients diagnosed with non-CMD. A total of 21 MACE occurred during the 1 year of follow-up. Compared with non-CMD group, patients with CMD showed a significantly higher risk of MACE. A multivariate Cox regression model was conducted for the patients, and it was found thatcaIMR was a significant predictor of prognosis in STEMI patients (HR: 8.921). Patients with CMD were divided into culprit vascular CMD and non-culprit vascular CMD, and the result found that culprit vascular CMD was associated with the incidence of MACE (OR: 4.75) and heart failure (OR: 7.50).

CONCLUSION

CaIMR is a strong predictor of clinical outcomes and can provide an objective risk stratification for patients with STEMI. There is a strong correlation among leukocyte index, the use of furosemide, Killips classification, and clinical outcomes.

Predicting left ventricular remodeling post-MI through coronary physiological measurements based on computational fluid dynamics

Early detection of left ventricular remodeling (LVR) is crucial. While cardiac magnetic resonance (CMR) provides valuable information, it has limitations. Coronary angiography-derived fractional flow reserve (caFFR) and index of microcirculatory resistance (caIMR) offer viable alternatives. 157 patients with ST-segment elevation myocardial infarction (STEMI) undergoing primary percutaneous coronary intervention were prospectively included. 23.6% of patients showed LVR. Machine learning algorithms constructed three LVR prediction models: Model 1 incorporated clinical and procedural parameters, Model 2 added CMR parameters, and Model 3 included echocardiographic and functional parameters (caFFR and caIMR) with Model 1. The random forest algorithm showed robust performance, achieving AUC of 0.77, 0.84, and 0.85 for Models 1, 2, and 3. SHAP analysis identified top features in Model 2 (infarct size, microvascular obstruction, admission hemoglobin) and Model 3 (current smoking, caFFR, admission hemoglobin). Findings indicate coronary physiology and echocardiographic parameters effectively predict LVR in patients with STEMI, suggesting their potential to replace CMR.

Coronary slow flow and angiography-derived index of microcirculatory resistance as prognostic predictors in patients with angina and normal coronary arteries: a retrospective cohort study

BACKGROUND

This study aims to investigate prognostic implications of coronary slow flow (CSF) and angiography-derived index of microcirculatory resistance (caIMR) in patients with angina and normal coronary arteries.

METHODS

A total of 582 patients were enrolled with angiographically normal coronary arteries. caIMR was calculated using a commercial software. Patients were followed up for a median of 45 months. The primary endpoint was defined as major adverse cardiovascular events (MACEs) comprising death, myocardial infarction and readmission for angina or heart failure.

RESULTS

CSF was diagnosed when TIMI grade 2 flow presented in at least one coronary artery. Multivariate analysis indicated TIMI-flow-based determination of CSF was not significantly associated with MACEs [hazard ratio (HR): 2.14; 95% confidence interval (CI): 0.87-5.31; p = 0.099), while caIMR >42 (HR: 2.53; 95% CI: 1.02-6.32; p = 0.047) were independent predictors of MACEs. Incorporation of caIMR improved the area under the curve from 0.587 to 0.642.

CONCLUSIONS

caIMR was an independent prognostic factor of long-term cardiovascular events in patients with CSF. Evaluation of caIMR improved the risk stratification of patients with angiographically-normal coronary arteries.

A new computational fluid dynamics based noninvasive assessment of portacaval pressure gradient

Accurate assessment of portacaval pressure gradient (PCG) in patients with portal hypertension (PH) is of great significance both for diagnosis and treatment. This study aims to develop a noninvasive method for assessing PCG in PH patients and evaluate its accuracy and effectiveness. This study recruited 37 PH patients treated with transjugular intrahepatic portosystemic shunt (TIPS). computed tomography angiography was used to create three dimension (3D) models of each patient before and after TIPS. Doppler ultrasound examinations were conducted to obtain the patient's portal vein flow (or splenic vein and superior mesenteric vein). Using computational fluid dynamics (CFD) simulation, the patient's pre-TIPS and post-TIPS PCG was determined by the 3D models and ultrasound measurements. The accuracy of these noninvasive results was then compared to clinical invasive measurements. The results showed a strong linear correlation between the PCG simulated by CFD and the clinical invasive measurements both before and after TIPS (R2 = 0.998, P < 0.001 and R2 = 0.959, P < 0.001). The evaluation accuracy of this noninvasive method reached 94 %, and the influence of ultrasound result errors on the numerical accuracy was found to be marginal if the error was less than 20 %. Furthermore, the information about the hemodynamic environment in the portal system was obtained by this numerical method. Spiral flow patterns were observed in the portal vein of some patients. In a conclusion, this study proposes a noninvasive numerical method for assessing PCG in PH patients before and after TIPS. This method can assist doctors in accurately diagnosing patients and selecting appropriate treatment plans. Additionally, it can be used to further investigate potential biomechanical causes of complications related to TIPS in the future.

Diagnostic performances of Nonhyperemic Pressure Ratios and Coronary Angiography-Based Fractional Flow Reserve against conventional Wire-Based Fractional Flow Reserve

BACKGROUND

Nonhyperemic pressure ratios (NHPRs) have been proposed as alternatives to fractional flow reserve (FFR) without induction of hyperemia. More recently, imaging based-FFR estimation, especially coronary angiography-derived FFR (Angio-FFR) measurement, is proposed to estimate wire-based FFR. However, little is known about the diagnostic performance of these indices against conventional FFR.

AIMS

We aimed to assess and compare the diagnostic performance of both NHPRs and coronary Angio-FFR against wire-based conventional FFR.

METHODS

PubMed and Embase databases were systematically searched for peer-reviewed original articles up to 08/2022. The primary outcomes were the pooled sensitivity and specificity as well as the area under the curve (AUC) of the summary receiver-operating characteristic curve of those indices.

RESULTS

A total of 6693 records were identified after a literature search, including 37 reports for NHPRs and 34 for Angio-FFR. Overall, NHPRs have a lower diagnostic performance in estimating wire-based FFR with an AUC of 0.85 (0.81, 0.88) when compared with Angio-FFR of 0.95 (0.93, 0.97). When all four modalities of NHPRs (iFR, Pd/Pa, DPR, RFR) were compared, those had overlapping AUCs without major differences among each other. Similarly, when the two most commonly used Angio-FFR (QFR, FFR angio ) were compared, those had overlapping AUCs without major differences among each other.

CONCLUSION

Angio-FFR may offer a better estimation of wire-based FFR than NHPRs. Our results support a wider use of Angio-FFR in the cardiac catheterization laboratory to streamline our workflow for coronary physiologic assessment.

CLASSIFICATIONS

FFR,, stable ischemic disease and non-ST elevation acute coronary syndrome.

Coronary angiography-derived index of microcirculatory resistance and evolution of infarct pathology after ST-segment-elevation myocardial infarction

AIMS

This study sought to evaluate the association of coronary angiography-derived index of microcirculatory resistance (angio-IMR) measured after primary percutaneous coronary intervention (PPCI) with the evolution of infarct pathology during 3-month follow-up after ST-segment-elevation myocardial infarction (STEMI).

METHODS AND RESULTS

Patients with STEMI undergoing PPCI were prospectively enrolled between October 2019 and August 2021. Angio-IMR was calculated using computational flow and pressure simulation immediately after PPCI. Cardiac magnetic resonance (CMR) imaging was performed at a median of 3.6 days and 3 months. A total of 286 STEMI patients (mean age 57.8 years, 84.3% men) with both angio-IMR and CMR at baseline were included. High angio-IMR (>40 U) occurred in 84 patients (29.4%) patients. Patients with angio-IMR >40 U had a higher prevalence and extent of MVO. An angio-IMR >40 U was a multivariable predictor of infarct size with a three-fold higher risk of final infarct size >25% (adjusted OR 3.00, 95% CI 1.23-7.32, P = 0.016). Post-procedure angio-IMR >40 U significantly predicted presence (adjusted OR 5.52, 95% CI 1.65-18.51, P = 0.006) and extent (beta coefficient 0.27, 95% CI 0.01-0.53, P = 0.041) of myocardial iron at follow-up. Compared with patients with angio-IMR ≤40 U, those with angio-IMR >40 U had less regression of infarct size and less resolution of myocardial iron at follow-up.

CONCLUSIONS

Angio-IMR immediately post-PPCI showed a significant association with the extent and evolution of infarct pathology. An angio-IMR >40 U indicated extensive microvascular damage with less regression of infarct size and more persistent iron at follow-up.

Coronary microvascular dysfunction and myocardial infarction with non-obstructive coronary arteries: Where do we stand?

In the past decade, scientific and clinical research has provided a translational perspective on myocardial infarction (MI) with non-obstructive coronary arteries (MINOCA). MINOCA is characterized by clinical documentation of an acute MI but angiography shows no significant coronary artery obstruction (stenosis <50%). The prevalence of MINOCA is estimated to range from approximately 6 to 10% among MI patients, and those with this condition have a poor prognosis, experiencing high rates of mortality, rehospitalization, and socioeconomic burden. MINOCA represents a major unmet need in cardiovascular medicine, with uncertain clinical management. It is a complex condition that can be caused by various factors, including atherosclerosis, plaque rupture, coronary vasospasm, and microvascular dysfunction. Effective management of MINOCA depends on identifying the underlying mechanism of the infarction, thus a systematic diagnostic approach is recommended. Contemporary data shows that a significant number of patients exhibit structural and functional abnormalities in coronary microcirculation, which is referred to as coronary microvascular dysfunction (CMD). CMD plays a crucial role in patients with signs and symptoms of myocardial ischemia and non-obstructive coronary artery stenosis, including MINOCA. Furthermore, conducting a thorough evaluation of coronary function can have significant prognostic and therapeutic implications, since personalized patient management strategies based on this assessment have been shown to improve symptoms and prognosis. Therefore, an accurate and timely diagnosis of CMD is essential for effective patient management, which can be achieved through various invasive and non-invasive methods. This review will discuss the pathophysiological understanding, current diagnostic techniques, and management strategies of patients with MINOCA and CMD.

A multi-stage neural network approach for coronary 3D reconstruction from uncalibrated X-ray angiography images

We present a multi-stage neural network approach for 3D reconstruction of coronary artery trees from uncalibrated 2D X-ray angiography images. This method uses several binarized images from different angles to reconstruct a 3D coronary tree without any knowledge of image acquisition parameters. The method consists of a single backbone network and separate stages for vessel centerline and radius reconstruction. The output is an analytical matrix representation of the coronary tree suitable for downstream applications such as hemodynamic modeling of local vessel narrowing (i.e., stenosis). The network was trained using a dataset of synthetic coronary trees from a vessel generator informed by both clinical image data and literature values on coronary anatomy. Our multi-stage network achieved sub-pixel accuracy in reconstructing vessel radius (RMSE = 0.16 ± 0.07 mm) and stenosis radius (MAE = 0.27 ± 0.18 mm), the most important feature used to inform diagnostic decisions. The network also led to 52% and 38% reduction in vessel centerline reconstruction errors compared to a single-stage network and projective geometry-based methods, respectively. Our method demonstrated robustness to overcome challenges such as vessel foreshortening or overlap in the input images. This work is an important step towards automated analysis of anatomic and functional disease severity in the coronary arteries.

Comparison of 2D-QCA, 3D-QCA and coronary angiography derived FFR in predicting myocardial ischemia assessed by CZT-SPECT MPI

BACKGROUND

Angiography derived fractional flow reserve (angio-FFR) has been proposed. This study aimed to assess its diagnostic performance with cadmium-zinc-telluride single emission computed tomography (CZT-SPECT) as reference.

METHODS AND RESULTS

Patients underwent CZT-SPECT within 3 months of coronary angiography were included. Angio-FFR computation was performed using computational fluid dynamics. Percent diameter (%DS) and area stenosis (%AS) were measured by quantitative coronary angiography. Myocardial ischemia was defined as a summed difference score ≥ 2 in a vascular territory. Angio-FFR ≤ 0.80 was considered abnormal. 282 coronary arteries in 131 patients were analyzed. Overall accuracy of angio-FFR to detect ischemia on CZT-SPECT was 90.43%, with a sensitivity of 62.50% and a specificity of 98.62%. The diagnostic performance (= area under ROC = AUC) of angio-FFR [AUC = 0.91, 95% confidence intervals (CI) 0.86-0.95] was similar as those of %DS (AUC = 0.88, 95% CI 0.84-0.93, p = 0.326) and %AS (AUC = 0.88, 95% CI 0.84-0.93 p = 0.241) by 3D-QCA, but significantly higher than those of %DS (AUC = 0.59, 95% CI 0.51-0.67, p < 0.001) and %AS (AUC = 0.59, 95% CI 0.51-0.67, p < 0.001) by 2D-QCA. However, in vessels with 50-70% stenoses, AUC of angio-FFR was significantly higher than those of %DS (0.80 vs. 0.47, p < 0.001) and %AS (0.80 vs. 0.46, p < 0.001) by 3D-QCA and %DS (0.80 vs. 0.66, p = 0.036) and %AS (0.80 vs. 0.66, p = 0.034) by 2D-QCA.

CONCLUSION

Angio-FFR had a high accuracy in predicting myocardial ischemia assessed by CZT-SPECT, which is similar as 3D-QCA but significantly higher than 2D-QCA. While in intermediate lesions, angio-FFR is better than 3D-QCA and 2D-QCA in assessing myocardial ischemia.

Clinical Value of Computational Angiography-derived Fractional Flow Reserve in Stable Coronary Artery Disease

The utilization of FFR remains low. Our study evaluated the per-vessel prognostic value of computational pressure-flow dynamics-derived FFR (caFFR) among patients with stable coronary artery disease. A total of 3329 vessels from 1308 patients were included and analysed. They were stratified into ischaemic (caFFR ≤ 0.8) and non-ischaemic (caFFR > 0.8) cohorts, and the associations between PCI and outcomes were evaluated. The third cohort comprised all included vessels, and the associations between treatment adherent-to-caFFR (PCI in vessels with caFFR ≤ 0.8 and no PCI in vessels with caFFR > 0.8) and outcomes were evaluated. The primary outcome was VOCE, defined as a composite of vessel-related cardiovascular mortality, non-fatal myocardial infarction, and repeat revascularization. PCI was associated with a lower 3-year risk of VOCE in the ischaemic cohort (HR, 0.44; 95% CI, 0.26-0.74; P = 0.002) but not in the non-ischaemic cohort. The risk of VOCE was lower in the adherent-to-caFFR group (n = 2649) (HR, 0.69; 95% CI, 0.48-0.98; P = 0.039). A novel index that uses coronary angiography images to estimate FFR may have substantial clinical value in guiding management among patients with stable coronary artery disease.

Diagnostic Performance of Intracoronary Optical Coherence Tomography-Modulated Quantitative Flow Ratio for Assessing Coronary Stenosis

Background

A novel method for fast computation of Murray law-based quantitative flow ratio (μQFR) from coregistered angiography and optical coherence tomography (OCT) was recently developed. This study aimed to evaluate the diagnostic performance of this OCT-modulated μQFR (OCT-μFR).

Methods

Patients who underwent coronary angiography, OCT, and fractional flow reserve (FFR) were retrospectively enrolled. μQFR was computed from a single angiographic projection. Subsequently, OCT image pullback was coregistered with the angiogram, and OCT-μFR was calculated based on the coregistered data. The same cut-off value of 0.80 was used for OCT-μFR, μQFR, and FFR to define ischemia.

Results

A paired comparison of OCT-μFR and μQFR was performed in 269 vessels from 218 patients. The mean FFR was 0.81 ± 0.11, and 45.0% of vessels had an FFR ≤0.80. OCT-μFR showed a better correlation with FFR than μQFR (r = 0.83 vs 0.76, P = .018) and numerically higher diagnostic performance (area under the curve [AUC] = 0.95 vs 0.92, P = .057). Sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for OCT-μFR to identify ischemia-causing stenosis were 89.3%, 93.2%, 91.5%, 91.4%, 13.2, and 0.1, respectively. In addition, OCT-μFR showed significantly higher diagnostic performance compared with μQFR in vessels with suboptimal angiographic image quality (AUC = 0.93 vs 0.87, P = .028) and tandem lesions (AUC = 0.94 vs 0.87, P = .017).

Conclusions

Computation of OCT-μFR was feasible and accurately identified physiologically significant coronary stenosis with simultaneous morphological assessment. In vessels with suboptimal angiographic image quality or tandem lesions, OCT-μFR had a higher diagnostic performance than angiography-based μQFR.

Coronary angiography-derived index for assessing microcirculatory resistance in patients with non-obstructed vessels: The FLASH IMR study

BACKGROUND

Assessing index of microcirculatory resistance (IMR) is customarily performed using intracoronary wires fitted with sensors by at least 3 intracoronary injections of 3 to 4 mL of room-temperature saline during sustained hyperemia, which is time- and cost-consuming.

METHODS

The FLASH IMR study is a prospective, multicenter, randomized study to assess the diagnostic performance of coronary angiography-derived IMR (caIMR) in patients with suspected myocardial ischemia with nonobstructive coronary arteries using wire-based IMR as a reference. The caIMR was calculated by an optimized computational fluid dynamics model simulating hemodynamics during diastole based on coronary angiograms. TIMI frame count and aortic pressure were included in computation. caIMR was determined onsite in real time and compared blind to wire-based IMR by an independent core laboratory, using wire-based IMR ≥25 units as indicative of abnormal coronary microcirculatory resistance. The primary endpoint was the diagnostic accuracy of caIMR, using wire-based IMR as a reference, with a pre-specified performance goal of 82%.

RESULTS

A total of 113 patients underwent paired caIMR and wire-based IMR measurements. Order of performance of tests was based on randomization. Diagnostic accuracy, sensitivity, specificity, positive and negative predictive values of caIMR were 93.8% (95% CI: 87.7%-97.5%), 95.1% (95% CI: 83.5%- 99.4%), 93.1% (95% CI: 84.5%-97.7%), 88.6% (95% CI: 75.4%-96.2%) and 97.1% (95% CI: 89.9%-99.7%). The receiver-operating curve for caIMR to diagnose abnormal coronary microcirculatory resistance had area under the curve of 0.963 (95% CI: 0.928-0.999).

CONCLUSIONS

Angiography-based caIMR has a good diagnostic yield with wire-based IMR.

CLINICALTRIALS

GOV IDENTIFIER

NCT05009667.

Accuracy and Reproducibility of Coronary Angiography-Derived Fractional Flow Reserve in the Assessment of Coronary Lesion Severity

Purpose

Coronary angiography-derived fractional flow reserve (caFFR) is a novel computational flow dynamics (CFD)-derived assessment of coronary vessel flow with good diagnostic performance. Herein, we performed a retrospective study to evaluate the reproducibility of caFFR findings between observers and investigate the diagnostic performance of caFFR for coronary stenosis defined as FFR ≤0.80, especially in the grey zone (0.75≤caFFR ≤0.80).

Patients and Methods

A total of 150 patients (167 coronary vessels) underwent caFFR (with FlashAngio used for calculation of flow variables) and subsequent invasive fractional flow reserve (FFR) measurements. Outcomes, including reproducibility, were compared for vessels in and outside the grey zone.

Results

The correlation of caFFR findings was good between the two laboratories (r = 0.723, p<0.001). The AUC of ROC were both high for caFFR-CoreLab1 and caFFR-CoreLab2 (0.975 and 0.883). The diagnostic accuracy, sensitivity, specificity, and negative and positive predictive values were not significantly different between the two laboratories (p>0.05). caFFR had a strong correlation with measures to FFR (r=0.911, p<0.001). There was no systematic difference between caFFR and FFR on Bland-Altman analysis in and outside the grey zone. There was no difference in diagnostic accuracy between the grey and non-grey zones in the prediction of FFR ≤0.80 (p=0.09).

Conclusion

The inter-observer reproducibility for caFFR was high, and the diagnostic accuracy of caFFR was good compared to that of FFR.

Applied coronary physiology for planning and guidance of percutaneous coronary interventions. A clinical consensus statement from the European Association of Percutaneous Cardiovascular Interventions (EAPCI) of the European Society of Cardiology

The clinical value of fractional flow reserve and non-hyperaemic pressure ratios are well established in determining an indication for percutaneous coronary intervention (PCI) in patients with coronary artery disease (CAD). In addition, over the last 5 years we have witnessed a shift towards the use of physiology to enhance procedural planning, assess post-PCI functional results, and guide PCI optimisation. In this regard, clinical studies have reported compelling data supporting the use of longitudinal vessel analysis, obtained with pressure guidewire pullbacks, to better understand how obstructive CAD contributes to myocardial ischaemia, to establish the likelihood of functionally successful PCI, to identify the presence and location of residual flow-limiting stenoses and to predict long-term outcomes. The introduction of new functional coronary angiography tools, which merge angiographic information with fluid dynamic equations to deliver information equivalent to intracoronary pressure measurements, are now available and potentially also applicable to these endeavours. Furthermore, the ability of longitudinal vessel analysis to predict the functional results of stenting has played an integral role in the evolving field of simulated PCI. Nevertheless, it is important to have an awareness of the value and challenges of physiology-guided PCI in specific clinical and anatomical contexts. The main aim of this European Association of Percutaneous Cardiovascular Interventions clinical consensus statement is to offer up-to-date evidence and expert opinion on the use of applied coronary physiology for procedural PCI planning, disease pattern recognition and post-PCI optimisation.

Prognostic Significance of Coronary Microvascular Dysfunction in Patients With Heart Failure With Preserved Ejection Fraction

BACKGROUND

The prognostic impact of coronary microvascular dysfunction (CMD) has been scarcely addressed in heart failure with preserved ejection fraction (HFpEF). This study investigated the prevalence and prognostic significance of CMD as measured by a novel pressure wire-free coronary angiography-derived index of microcirculatory resistance (caIMR) on clinical outcomes.

METHODS

Patients diagnosed with HFpEF from 2019 to 2021 were enrolled retrospectively. caIMR was used to quantify microvascular function, and patients were categorised into 2 groups based on their caIMR. The primary end points were composite of all-cause death and heart failure rehospitalisation.

RESULTS

Of 137 HFpEF patients, CMD (defined as caIMR ≥ 25) was present in 88 patients (64.2%). Forty-five patients (32.8%) experienced composite events during a mean follow-up of 15 months. Compared with patients with caIMR < 25, those with caIMR ≥ 25 had a notably higher incidence of composite events (16.3% vs 42.0%; P = 0.002). On survival analysis, patients with caIMR ≥ 25 demonstrated a worse prognosis than those with caIMR < 25 for composite events (P = 0.006). Patients with caIMR ≥ 25 in multiple coronary arteries showed a trend to worse outcome than those with caIMR ≥ 25 in a single coronary artery (log-rank P = 0.056). In adjusted analysis, caIMR ≥ 25 was independently predictive of adverse outcomes (adjusted hazard ratio 2.93, 95% confidence interval [CI] 1.28-6.70; P = 0.010). caIMR displayed a significant predictive power for adverse event prediction (area under the receiver operating characteristic curve 0.767, 95% CI 0.677-0.858; P < 0.001).

CONCLUSIONS

CMD is highly prevalent and is an independent predictor of adverse outcomes in HFpEF patients. Assessment of CMD may identify high-risk patients early for intensified treatment and risk-factor management.

Current status and future perspectives of fractional flow reserve derived from invasive coronary angiography

Assessment of the functional significance of coronary artery stenosis using invasive measurement of fractional flow reserve (FFR) or non-hyperemic indices has been shown to be safe and effective in making clinical decisions on whether to perform percutaneous coronary intervention (PCI). Despite strong evidence from clinical trials, utilization of these techniques is still relatively low worldwide. This may be to some extent attributed to factors that are inherent to invasive measurements like prolongation of the procedure, side effects of drugs that induce hyperemia, additional steps that the operator should perform, the possibility to damage the vessel with the wire, and additional costs. During the last few years, there was a growing interest in the non-invasive assessment of coronary artery lesions, which may provide interventionalist with important physiological information regarding lesion severity and overcome some of the limitations. Several dedicated software solutions are available on the market that could provide an estimation of FFR using 3D reconstruction of the interrogated vessel derived from two separated angiographic projections taken during diagnostic coronary angiography. Furthermore, some of them use data about aortic pressure and frame count to more accurately calculate pressure drop (and FFR). The ideal non-invasive system should be integrated into the workflow of the cath lab and performed online (during the diagnostic procedure), thereby not prolonging procedural time significantly, and giving the operator additional information like vessel size, lesion length, and possible post-PCI FFR value. Following the development of these technologies, they were all evaluated in clinical trials where good correlation and agreement with invasive FFR (considered the gold standard) were demonstrated. Currently, only one trial (FAVOR III China) with clinical outcomes was completed and demonstrated that QFR-guided PCI may provide better results at 1-year follow-up as compared to the angiography-guided approach. We are awaiting the results of a few other trials with clinical outcomes that test the performance of these indices in guiding PCI against either FFR or angiography-based approach, in various clinical settings. Herein we will present an overview of the currently available data, a critical review of the major clinical trials, and further directions of development for the five most widely available non-invasive indices: QFR, vFFR, FFRangio, caFFR, and AccuFFRangio.

Coronary Angiography Upgraded by Imaging Post-Processing: Present and Future Directions

Advances in computer technology and image processing now allow us to obtain from angiographic images a large variety of information on coronary physiology without the use of a guide-wire as a diagnostic information equivalent to FFR and iFR but also information allowing for the performance of a real virtual percutaneous coronary intervention (PCI) and finally the ability to obtain information to optimize the results of PCI. With specific software, it is now possible to have a real upgrading of invasive coronary angiography. In this review, we present the different advances in this field and discuss the future perspectives offered by this technology.

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

BACKGROUND

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.

STUDY DESIGN AND OBJECTIVES

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.

CONCLUSIONS

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.

The prognostic value and economic benefits of coronary angiography-derived fractional flow reserve-guided strategy in patients with coronary artery disease

Objective

This study aims to investigate the prognostic value and economic benefit of coronary angiography-derived fractional flow reserve (caFFR) guided percutaneous coronary intervention (PCI) in patients with coronary artery disease.

Methods

All patients with coronary artery disease (CAD) who underwent coronary angiography in our center between April 2021 and November 2021 were retrospectively enrolled and divided into the caFFR guidance group (n = 160) and angiography guidance group (n = 211). A threshold of caFFR≤0.8 was used for revascularization. Otherwise, delayed PCI was preferred. The patients were prospectively followed up by telephone or outpatient service at six months for major adverse cardiovascular events (MACE) of all-cause death, myocardial infarction or target vessel revascularization, stent thrombosis, and stroke. All in-hospital expenses were recorded, including initial hospitalization and re-hospitalization related to MACE.

Results

There was no significant difference in the baseline characteristics between the two groups. There were 2 (1.2%) patients in the caFFR guidance group and 5 (2.4%) patients in the angiography guidance group with MACE events during the following six months. Compared with angiography guidance, caFFR guidance reduced the revascularization rate (63.7% vs. 84.4%, p = 0.000), the average length of stents implanted (0.52 ± 0.88 vs. 1.1 ± 1.4, P < 0.001). The cost of consumables in the caFFR guidance group was significantly lower than that in the angiography guidance group (33257 ± 19595 CNY vs. 38341 ± 16485 CNY, P < 0.05).

Conclusion

Compared with coronary angiography guidance, caFFR guidance is of great significance in reducing revascularization and cost, which has significant health and economic benefits.

Diagnostic Accuracy of Artificial Intelligence-Based Angiography-Derived Fractional Flow Reserve Using Pressure Wire-Based Fractional Flow Reserve as a Reference

BACKGROUND

Angiographic fractional flow reserve (angioFFR) is a novel artificial intelligence (AI)-based angiography-derived fractional flow reserve (FFR) application. We investigated the diagnostic accuracy of angioFFR to detect hemodynamically relevant coronary artery disease.

METHODS AND RESULTS

Consecutive patients with 30-90% angiographic stenoses and invasive FFR measurements were included in this prospective, single-center study conducted between November 2018 and February 2020. Diagnostic accuracy was assessed using invasive FFR as the reference standard. In patients undergoing percutaneous coronary intervention, gradients of invasive FFR and angioFFR in the pre-senting segments were compared. We assessed 253 vessels (200 patients). The accuracy of angioFFR was 87.7% (95% confidence interval [CI] 83.1-91.5%), with a sensitivity of 76.8% (95% CI 67.1-84.9%), specificity of 94.3% (95% CI 89.5-97.4%), and area under the curve of 0.90 (95% CI 0.86-0.93%). AngioFFR was well correlated with invasive FFR (r=0.76; 95% CI 0.71-0.81; P<0.001). The agreement was 0.003 (limits of agreement: -0.13, 0.14). The FFR gradients of angioFFR and invasive FFR were comparable (n=51; mean [±SD] 0.22±0.10 vs. 0.22±0.11, respectively; P=0.87).

CONCLUSIONS

AI-based angioFFR showed good diagnostic accuracy for detecting hemodynamically relevant stenosis using invasive FFR as the reference standard. The gradients of invasive FFR and angioFFR in the pre-stenting segments were comparable.

Anonymous Comparison of Various Angiography-Derived Fractional Flow Reserve Software With Pressure-Derived Physiological Assessment

BACKGROUND

Software to compute angiography-derived fractional flow reserve (angio-FFR) have been validated against pressure wire-derived fractional flow reserve (PW-FFR) with an area under the receiver-operating characteristic curve (AUC) of 0.93 to 0.97.

OBJECTIVES

The aim of this study was to investigate diagnostic accuracies of 5 angio-FFR software/methods by an independent core lab in a prospective cohort of 390 vessels with carefully documented sites of PW-FFR and pressure wire-derived instantaneous wave-free ratio.

METHODS

One "matcher investigator" colocalized on angiography the sites of pressure wire measurement with angio-FFR measurements and provided the same 2 optimal angiographic views and frame selection to independent analysts who were blinded to invasive physiological results and results from other software. The results were anonymized and randomly presented. The AUC of each angio-FFR was compared with 2-dimensional quantitative coronary angiography (QCA) percent diameter stenosis (%DS) using a 2-tailed paired comparison of AUC.

RESULTS

All 5 software/methods yielded a high proportion of analyzable vessels (A: 100%, B: 100%, C: 92.1%, D: 99.5%, and E: 92.1%). The AUCs for predicting fractional flow reserve ≤0.8 for software A, B, C, D, E, and 2-dimensional QCA %DS were 0.75, 0.74, 0.74, 0.73, 0.73, and 0.65, respectively. The AUC for each angio-FFR was significantly greater than that for 2-dimensional QCA %DS.

CONCLUSIONS

This head-to-head comparison by an independent core lab demonstrated that the diagnostic accuracy of various angio-FFR software for predicting PW-FFR ≤0.80 was useful, with a higher discrimination compared with 2-dimensional QCA %DS; however, it did not reach the diagnostic accuracy previously reported in validation studies of various vendors. Therefore, the intrinsic clinical value of "angiography-derived fractional flow reserve" requires confirmation in large clinical trials.

A novel method for calculating CTFFR based on the flow ratio between stenotic coronary and healthy coronary

BACKGROUND

Epicardial coronary stenosis may lead to myocardial ischaemia, and the resulting obstructive coronary artery disease is one of the leading causes of death. CT-derived fractional flow reserve (CT-FFR) has been clinically shown to be an effective method for the noninvasive assessment of coronary artery stenosis. However, this method has the problem that the measurement result is affected by the selected measurement position.

OBJECTIVES

This study was to obtain a novel flow-based approach to coronary CTFFR (CTQFFR), which was not affected by the measurement location.

METHODS

This study established healthy-assumed coronary arteries based on narrowed coronary arteries. Based on the assumption that the microvascular resistance remains unchanged in the short term after coronary stenosis treatment, the blood flow in the stenotic coronary artery and the healthy-assumed coronary artery was obtained by numerical simulation, and the CTQFFR based on the blood flow ratio was calculated. The functional relationship between CTQFFR and FFR was fitted by the results of 20 cases.

RESULTS

In this study, the functional relationship between CTQFFR and FFR was fitted by a quadratic curve, and the variance was 0.8744; the functional relationship between CTQFFR and pressure-based approach to coronary CTFFR (CTPFFR) was fitted by a primary curve, and the variance was 0.9971. There was coronary artery growth in all 20 cases. Preliminary validation results using 10 cases showed 100% accuracy in determining whether coronary artery stenosis required for clinical intervention. The relative error of the coefficient with the results proposed in a previous study was 0.316%.

CONCLUSION

This study proposes a new method for calculating coronary CTFFR, namely, coronary CTQFFR, which is the flow ratio between stenotic coronary and healthy-assumed coronary. This method solves the problem that the downstream CTFFR of coronary stenosis is related to the selected location, which effectively improves the CTFFR at the critical value (CTFFR= 0.8) near reliability. Preliminary research results show that the method obtained in this study has a high accuracy for determining whether there is significant coronary stenosis. However, large multi-centre validation for the feasibility of this method was necessary in our future work.

Prognostic value of combined coronary angiography-derived IMR and myocardial perfusion imaging by CZT SPECT in INOCA

BACKGROUND

A significant proportion of ischemia with non-obstructive coronary artery disease (INOCA) demonstrate coronary microvascular dysfunction (CMD), a condition associated with abnormal myocardial perfusion imaging (MPI) and adverse outcomes. Coronary angiography-derived index of microvascular resistance (caIMR) is a novel non-invasive technique to assess CMD. We aimed to investigate the prognostic value of combined caIMR and MPI by CZT SPECT in INOCA patients.

METHODS

Consecutive 151 patients with chest pain and < 50% coronary stenosis who underwent coronary angiography and MPI within 3 months were enrolled. caIMR was calculated by computational pressure-flow dynamics. CMD was defined as caIMR ≥ 25. The endpoint was major adverse cardiac events (MACE: cardiovascular death, nonfatal myocardial infarction, revascularization, angina-related rehospitalization, heart failure, and stroke).

RESULTS

Of all INOCA patients, CMD was present in 93 (61.6%) patients. The prevalence of abnormal MPI was significantly higher in CMD compared with non-CMD patients (40.9% vs 13.8%, P < .001). CMD showed a higher risk of MACE than non-CMD patients. Patients with both CMD and abnormal MPI had the worst prognosis, followed by patients with CMD and normal MPI (log-rank P < .001). Cox regression analysis identified CMD (HR 3.121, 95%CI 1.221-7.974, P = .017) and MPI (HR 2.704, 95%CI 1.030-7.099, P = .043) as predictive of MACE. The prognostic value of INOCA patients enhanced significantly by adding CMD and MPI to the model with clinical risk factors (AUC = 0.777 vs 0.686, P = .030).

CONCLUSION

caIMR-derived CMD is associated with increased risk of MACE among INOCA patients. Patients with abnormalities on both caIMR and MPI had the worse outcomes.

Pre-stenting angiography-FFR based physiological map provides virtual intervention and predicts physiological and clinical outcomes

BACKGROUND

Angiography-derived fractional flow reserve (FFR) (angio-FFR) has been validated against FFR and could provide virtual pullback. However, whether a physiological map can be generated by angio-FFR and its clinical value remains unclear. We aimed to investigate the feasibility of physiological map created from angio-FFR pullback and its value in predicting physiological and clinical outcomes after stenting.

METHODS

An angio-FFR physiological map was generated by overlaying the virtual pullback onto coronary angiogram, to calculate physiological stenosis severity, length, and intensity (Δangio-FFR/mm). This map in combination with virtual stenting was used to predict the best-case post-percutaneous coronary intervention (PCI) angio-FFR (angio-FFR_predicted ) according to the stented segments, and this was compared with the actual achieved post-PCI angio-FFR (angio-FFR_achieved ). Additionally, prognostic value of predicted angio-FFR was investigated.

RESULTS

Three hundred twenty-nine vessels with paired analyzable pre- and post-PCI angio-FFR were included. Physiological map was created successfully in all vessels. After successful PCI, angio-FFR_predicted and angio-FFR_achieved were significantly correlated (r = 0.82, p < 0.001) with small difference (mean difference: -0.010 ± 0.035). In the virtual PCI only covering the segment with high angio-FFR intensity, the same physiological outcome can be achieved with shorter stent length (14.1 ± 8.9 vs. 34.5 ± 15.8 mm, p < 0.001). Suboptimal angio-FFR_predicted was associated with increased risk of 2-year vessel-oriented composite endpoint (adjusted hazard ratio: 3.71; 95% confidence interval: 1.50-9.17).

CONCLUSIONS

Angio-FFR pullback could provide a physiological map of the interrogated coronary vessels by integrating angio-FFR pullback and angiography. Before a PCI, the physiological map can predict the physiological and clinical outcomes after stenting.

Role of artificial intelligence and machine learning in interventional cardiology

Directed by two decades of technological processes and remodeling, the dynamic quality of healthcare data combined with the progress of computational power has allowed for rapid progress in artificial intelligence (AI). In interventional cardiology, AI has shown potential in providing data interpretation and automated analysis from electrocardiogram (ECG), echocardiography, computed tomography angiography (CTA), magnetic resonance imaging (MRI), and electronic patient data. Clinical decision support has the potential to assist in improving patient safety and making prognostic and diagnostic conjectures in interventional cardiology procedures. Robot-assisted percutaneous coronary intervention (R-PCI), along with functional and quantitative assessment of coronary artery ischemia and plaque burden on intravascular ultrasound (IVUS), are the major applications of AI. Machine learning (ML) algorithms are used in these applications, and they have the potential to bring a paradigm shift in intervention. Recently, an efficient branch of ML has emerged as a deep learning algorithm for numerous cardiovascular (CV) applications. However, the impact DL on the future of cardiology practice is not clear. Predictive models based on DL have several limitations including low generalizability and decision processing in cardiac anatomy.

The spectrum of angiography-derived IMR according to morphological and physiological coronary stenosis in patients with suspected myocardial ischemia

BACKGROUND

Coronary microvascular dysfunction is crucial in determining myocardial ischemia; however, the relationship between epicardial coronary diameter stenosis (DS) and the index of microcirculatory resistance (IMR) remains unclear. We sought to explore the distribution of coronary angiography-derived IMR (angio-IMR) in patients with suspected myocardial ischemia.

METHODS

The study included 480 patients with suspected myocardial ischemia, all of whom underwent coronary angiography. According to the severity of coronary DS, patients were divided into three groups: mild (DS < 50%), intermediate (DS 50%-70%), and severe (DS > 70%). Angio-IMR and fractional flow reserve (FFR) were calculated based on coronary angiography images through the principle of computational flow and pressure simulation.

RESULTS

Of the 480 patients, the mean age was 67.23 ± 9.44 years, with 55.4% male. There were 193 (40.2%) patients in the mild group, 189 (39.4%) patients in the intermediate group, and 98 (20.4%) patients in the severe group. The average angio-IMR of the mild group was 30.8 ± 14.9, which was significantly higher than those of the intermediate group (26.7 ± 13.0) and the severe group (17.9 ± 8.4) (p < .001). In the correlation analysis, angio-IMR was negatively correlated with DS (rho = -0.331, p = .001) and positively correlated with angio-FFR (rho = 0.483, p < .001). By multivariate logistic regression analysis, angio-FFR ≤ 0.8 (odds ratio, 0.184; 95% confidence interval, 0.106-0.321) was the only independent predictor of coronary microvascular dysfunction.

CONCLUSION

In patients with suspected myocardial ischemia, coronary microcirculation is significantly associated with morphological and physiological coronary stenosis. (ClinicalTrials.gov: NCT05435898).

Coronary Microcirculation: The Next Frontier in the Management of STEMI

Although the widespread adoption of timely invasive reperfusion strategies over the last two decades has significantly improved the prognosis of patients with ST-segment elevation myocardial infarction (STEMI), up to half of patients after angiographically successful primary percutaneous coronary intervention (PCI) still have signs of inadequate reperfusion at the level of coronary microcirculation. This phenomenon, termed coronary microvascular dysfunction (CMD), has been associated with impaired prognosis. The aim of the present review is to describe the collected evidence on the occurrence of CMD following primary PCI, means of assessment and its association with the infarct size and clinical outcomes. Therefore, the practical role of invasive assessment of CMD in the catheterization laboratory, at the end of primary PCI, is emphasized, with an overview of available technologies including thermodilution- and Doppler-based methods, as well as recently developing functional coronary angiography. In this regard, we review the conceptual background and the prognostic value of coronary flow reserve (CFR), index of microcirculatory resistance (IMR), hyperemic microvascular resistance (HMR), pressure at zero flow (PzF) and angiography-derived IMR. Finally, the so-far investigated therapeutic strategies targeting coronary microcirculation after STEMI are revisited.

Coronary Physiologic Assessment Based on Angiography and Intracoronary Imaging

Intracoronary physiology testing has evolved as a promising diagnostic approach in the management of patients with coronary artery disease. The value of hyperemic translesional pressure ratios to estimate the functional relevance of coronary stenoses is supported by a wealth of outcomes data. The continuing drive to further simplify this approach led to the development of non-hyperemic pressure-based indices. Recent attention has focused on estimating functional significance without invasively measuring coronary pressure through the measurement of virtual indices derived from the coronary angiogram. By offering a routine assessment of the physiology of all the major epicardial coronary vessels, angiogram-derived physiology has the potential to modify current practice by facilitating more accurate patient-level, vessel-level, and even lesion-level decision making. This article reviews the current state of angiogram-derived physiology and speculates on its potential impact on clinical practice, in continuation to the previously published article on coronary physiology in this journal.

Functional angiography-derived index of microcirculatory resistance validated with microvascular obstruction in cardiac magnetic resonance after STEMI

INTRODUCTION AND OBJECTIVES

The index of microcirculatory resistance (IMR) measured after primary percutaneous coronary intervention (PCI) for ST-segment elevation myocardial infarction (STEMI) is associated with microvascular obstruction (MVO) and adverse clinical events. To evaluate MVO after successful primary PCI for STEMI without pressure wires or hyperemic agents, we investigated the feasibility and usefulness of functional angiography-derived IMR (angio-IMR).

METHODS

The current study included a total of 285 STEMI patients who underwent primary PCI and cardiac magnetic resonance (CMR). Angio-IMR of the culprit vessel after successful primary PCI was calculated using commercial software. MVO, infarct size, and myocardial salvage index were assessed using CMR, which was obtained a median of 3.0 days [interquartile range, 3.0-5.0] after primary PCI.

RESULTS

Among the total population, 154 patients (54.0%) showed elevated angio-IMR (> 40 U) in the culprit vessel. MVO was significantly more prevalent in patients with angio-IMR> 40 U than in those with angio-IMR ≤ 40 U (88.3% vs 32.1%, P <.001). Infarct size, extent of MVO, and area at risk were significantly larger in patients with angio-IMR> 40 U than in those with angio-IMR ≤ 40 U (P <.001 for all). Angio-IMR showed a significantly higher discriminatory ability for the presence of MVO than thrombolysis in myocardial infarction flow grade or myocardial blush grade (area under the curve: 0.821, 0.504, and 0.496, respectively, P <.001).

CONCLUSIONS

Angio-IMR was significantly associated with CMR-derived infarct size, extent of MVO, and area at risk. An elevated angio-IMR (> 40 U) after primary PCI for STEMI was highly predictive of the presence of MVO in CMR. This trial was registered at ClnicalTrialsgov (Identifier: NCT04828681).

Incorporating clinical parameters to improve the accuracy of angiography-derived computed fractional flow reserve. EUROPEAN HEART JOURNAL. DIGITAL HEALTH 2022;3:481-488. [PMID: 36712154 PMCID: PMC9707918 DOI: 10.1093/ehjdh/ztac045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Aims

Angiography-derived fractional flow reserve (angio-FFR) permits physiological lesion assessment without the need for an invasive pressure wire or induction of hyperaemia. However, accuracy is limited by assumptions made when defining the distal boundary, namely coronary microvascular resistance (CMVR). We sought to determine whether machine learning (ML) techniques could provide a patient-specific estimate of CMVR and therefore improve the accuracy of angio-FFR.

Methods and results

Patients with chronic coronary syndromes underwent coronary angiography with FFR assessment. Vessel-specific CMVR was computed using a three-dimensional computational fluid dynamics simulation with invasively measured proximal and distal pressures applied as boundary conditions. Predictive models were created using non-linear autoregressive moving average with exogenous input (NARMAX) modelling with computed CMVR as the dependent variable. Angio-FFR (VIRTUheart™) was computed using previously described methods. Three simulations were run: using a generic CMVR value (Model A); using ML-predicted CMVR based upon simple clinical data (Model B); and using ML-predicted CMVR also incorporating echocardiographic data (Model C). The diagnostic (FFR ≤ or >0.80) and absolute accuracies of these models were compared. Eighty-four patients underwent coronary angiography with FFR assessment in 157 vessels. The mean measured FFR was 0.79 (±0.15). The diagnostic and absolute accuracies of each personalized model were: (A) 73% and ±0.10; (B) 81% and ±0.07; and (C) 89% and ±0.05, P < 0.001.

Conclusion

The accuracy of angio-FFR was dependent in part upon CMVR estimation. Personalization of CMVR from standard clinical data resulted in a significant reduction in angio-FFR error.

Drug-Coated Balloon Treatment for Possible Sequelae of Kawasaki Disease Evaluated by Multi-Modalities

The most devastating sequela of Kawasaki disease (KD) is coronary artery complications that may lead to myocardial infarction and cardiac mortality. Percutaneous coronary intervention (PCI) and bypass grafting are recommended for KD patients with inducible myocardial ischemia and amendable coronary anatomy. However, there are few reports about coronary revascularization with drug-eluting balloons among KD patients, especially at an early age. We present a case report of multi-modality guidance of PCI with a drug-coated balloon (DCB) for a young patient with acute coronary syndrome and a history of KD. Post-procedural optical coherence tomography, angiography-derived fractional flow reserve, and 12-month coronary artery magnetic resonance showed favorable outcomes. The present case indicated that DCB therapy with intravascular imaging and physiologic assessment guidance may be an alternative strategy to treat severe coronary artery stenosis in selected patients with KD.

Angiography derived assessment of the coronary microcirculation: is it ready for prime time?

INTRODUCTION

Non-obstructive coronary arteries (NOCA) are present in 39.7% to 62.4% of patients who undergo elective angiography. Coronary microcirculation (<400 µm) is not visible on angiography therefore functional assessment, invasive or non-invasive plays a prior role to help provide a more personalized diagnosis of angina.

AREA COVERED

In this review, we revise the pathophysiology, clinical importance and invasive assessment of the coronary microcirculation, and discuss angiography-derived indices of microvascular resistance. A comprehensive literature review over four decades is also undertaken.

EXPERT OPINION

The coronary microvasculature plays an important role in flow autoregulation and metabolic regulation. Invasive assessment of microvascular resistance is a validated modality with independent prognostic value, nevertheless, its routine application is hampered by the requirement of intravascular instrumentation and hyperaemic agents. The angiography-derived index of microvascular resistance has emerged as a promising surrogate in pilot studies, however, more data are needed to validate and compare the diagnostic and prognostic accuracy of different equations as well as to illustrate the relationship between angiography-derived parameters for epicardial coronary arteries and those for the microvasculature.

Angiographic Lesion Morphology Provides Incremental Value to Generalize Quantitative Flow Ratio for Predicting Myocardial Ischemia

Aim

The quantitative flow ratio (QFR) is favorable for functional assessment of coronary artery stenosis without pressure wires and induction of hyperemia. The aim of this study was to explore whether angiographic lesion morphology provides incremental value to generalize QFR for predicting myocardial ischemia in unselected patients.

Methods

This study was a substudy to the CT-FFR CHINA trial, referring 345 participants from five centers with suspected coronary artery disease on coronary CT angiography for diagnostic invasive coronary angiography (ICA). Fractional flow reserve (FFR) was measured in all vessels with 30–90% diameter stenosis. QFR was calculated in 186 lesions from 159 participants in a blinded manner. In addition, parameters to characterize lesion features were recorded or measured, including left anterior descending arteries (LADs)-involved lesions, side branch located at stenotic lesion (BL), multiple lesions (ML), minimal lumen diameter (MLD), reference lumen diameter (RLD), percent diameter stenosis (%DS), lesion length (LL), and LL/MLD4. Logistic regression was used to construct two kinds of models by combining single or two lesion parameters with the QFR. The performances of these models were compared with that of QFR on a per-vessel level.

Results

A total of 148 participants (mean age: 59.5 years; 101 men) with 175 coronary arteries were included for final analysis. In total, 81 (46%) vessels were considered hemodynamically significant. QFR correctly classified 82.29% of the vessels using FFR with a cutoff of 0.80 as reference standard. The area under the receiver operating characteristic curve (AUC) of QFR was 0.86 with a sensitivity, specificity, positive predictive value, and negative predictive value of 80.25, 84.04, 81.25, and 83.16%, respectively. The combined models (QFR + LAD + MLD, QFR + LAD + %DS, QFR + BL + MLD, and QFR + BL + %DS) outperformed QFR with higher AUCs (0.91 vs. 0.86, P = 0.02; 0.91 vs. 0.86, P = 0.02; 0.91 vs. 0.86, P = 0.02; 0.90 vs. 0.86, P = 0.03, respectively). Compared with QFR, the sensitivity of the combined models (QFR + BL and QFR + MLD) was improved (91.36 vs. 80.25%, 91.36 vs. 80.25%, respectively, both P &lt; 0.05) without compromised specificity or accuracy.

Conclusion

Combined with angiographic lesion parameters, QFR can be optimized for predicting myocardial ischemia in unselected patients.

Computational Pressure-Fluid Dynamics Applied to Index of Microcirculatory Resistance, Predicting the Prognosis of Drug-Coated Balloons Compared With Drug-Eluting Stents in STEMI Patients

Background: The impairment of microvascular injury on prognosis has increasingly drawn extensive awareness along with the high morbidity and mortality of ST-segment elevation myocardial infarction (STEMI) over recent years. The prognostic significance of computational pressure-fluid dynamics applied to index of microcirculatory resistance, derived from coronary angiography (CPFD-caIMR) in microvascular injury evaluation of STEMI patients remained inconclusive.

Methods: A total of 213 patients who met the inclusion criteria were selected retrospectively from 1003 STEMI patients from February 2018 to February 2020. Propensity score matching (PSM) was thereafter finished. CPFD-caIMR of all patients was obtained off-line using the software (FlashAngio, Rainmed Ltd., Suzhou, China) after PPCI. The primary endpoint was to compare the CPFD-caIMR and the incidence of major adverse cardiovascular events (MACEs) between drug-coated balloons (DCB) and drug-eluting stents (DES) groups. The correlation between CPFD-caIMR and MACEs was analyzed, and the prognosis of patients with STEMI was evaluated by CPFD-caIMR by multivariate regression analysis.

Results: Totally 213 STEMI patients with successful primary percutaneous coronary intervention (PPCI) were included, of whom 84 patients accepted DCB and 129 patients accepted DES respectively. Baseline characteristics and CPFD-caIMR were comparable between DCB and DES groups after PSM (62 patients in each group). CPFD-caIMR was not significantly different between two groups (DES vs. DCB: mean difference: 2.26, 95% CI -4.05 to 8.57, p = 0.45), and so was it when re-grouped by whether CPFD-caIMR > 40U or not (DES vs. DCB: 34.17% vs. 27.16%, p = 0.29). After a follow-up of 1 year, more MACEs occurred in DES group than DCB group (relative risk: 2.50, 95% CI 1.04 to 6.02, p = 0.04). The predictors of MACEs by multi-variate analysis found that, only time from symptom to balloon (p = 0.03) and time from door to balloon (p < 0.01) were independent predictors of MACEs, independent of treatment with DCB or DES intervention. Furthermore, CPFD-caIMR > 40U became an independent predictor of the combined events including cardiovascular deaths or heart failure readmission irrespective of PSM (odds ratio: 4.07, 95% CI: 1.06 to 7.66, p = 0.04).

Conclusion: CPFD-caIMR was a promising method for prognosis, which can predict CV death or heart failure readmission in STEMI patients. DCB was a possible strategy in PPCI of STEMI patients, not inferior to DES based on microvascular injury evaluated by CPFD-caIMR.

The Predictive Value of Combining Symptoms, Residual Syntax Score and Non-Invasive Tests in the Diagnosis of Significant Coronary Artery Disease in Elderly Post-PCI Patients

Purpose

To assess the diagnostic efficiency of a combination of symptoms, residual Syntax score (rSS) and non-invasive tests in elderly post-PCI patients.

Patients and Methods

This was a retrospective study that consecutively enrolled patients ≥60 years old with chronic coronary syndrome and previous stent implantation without lesions requiring further revascularization between March 2013 and June 2020. The patients were scheduled for exercise ECG, CCTA and invasive coronary angiography within 4 weeks. The study then calculated rSS and the sensitivity, specificity, positive and negative predictive values (PPV and NPV) and accuracy of symptoms, rSS, exercise ECG and CCTA, taking computational pressure-flow dynamics derived fractional flow reserve (caFFR) as the standard reference.

Results

A total of 114 patients were enrolled in this study, including 75 patients with caFFR-positive and 39 patients with caFFR-negative. The caFFR-positive group had more patients with typical angina. Furthermore, the rSS in the caFFR-positive group was higher than that in the caFFR-negative category (7.33 ± 6.56 vs 3.34 ± 4.26, p < 0.001). There was no significant difference in exercise ECG results between the two groups. However, the rate of positive CCTA in the caFFR-positive group was higher than that in the caFFR-negative category (89.33% vs 46.15%, p < 0.001). In addition, after combining symptoms, rSS and CCTA, the sensitivity, specificity, PPV, NPV and accuracy for diagnose were 77.5%, 84.2%, 90.2%, 66.7% and 79.8%, respectively.

Conclusion

The findings showed that exercise ECG had limited power to diagnose significant CAD in elderly post-PCI patients, but CCTA was more efficient. Moreover, combining symptoms, rSS and CCTA provided more accurate diagnostic performance with feasibility and safety.

Vessel fractional flow reserve (vFFR) for the assessment of stenosis severity: the FAST II study

BACKGROUND

Fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI) is superior to angiography-guided PCI. The clinical uptake of FFR has been limited, however, by the need to advance a wire in the coronary artery, the additional time required and the need for hyperaemic agents which can cause patient discomfort. FFR derived from routine coronary angiography eliminates these issues.

AIMS

The aim of this study was to assess the diagnostic performance and accuracy of three-dimensional quantitative coronary angiography (3D-QCA)-based vessel FFR (vFFR) compared to pressure wire-based FFR (≤0.80).

METHODS

The FAST II (Fast Assessment of STenosis severity) study was a prospective observational multicentre study designed to evaluate the diagnostic accuracy of vFFR compared to the reference standard (pressure wire-based FFR ≤0.80). A total of 334 patients from six centres were enrolled. Both site-determined and blinded independent core lab vFFR measurements were compared to FFR.

RESULTS

The core lab vFFR was 0.83±0.09 and pressure wire-based FFR 0.83±0.08. A good correlation was found between core lab vFFR and pressure wire-based FFR (R=0.74; p<0.001; mean bias 0.0029±0.0642). vFFR had an excellent diagnostic accuracy in identifying lesions with an invasive wire-based FFR ≤0.80 (area under the curve [AUC] 0.93; 95% confidence interval [CI]: 0.90-0.96; p<0.001). Positive predictive value, negative predictive value, diagnostic accuracy, sensitivity and specificity of vFFR were 90%, 90%, 90%, 81% and 95%, respectively.

CONCLUSIONS

3D-QCA-based vFFR has excellent diagnostic performance to detect FFR ≤0.80. The study was registered on clinicaltrials.gov under identifier NCT03791320.

Angiography-Based Fractional Flow Reserve: State of the Art

Purpose of Review

Three-dimensional quantitative coronary angiography-based methods of fractional flow reserve (FFR) derivation have emerged as an appealing alternative to conventional pressure-wire-based physiological lesion assessment and have the potential to further extend the use of physiology in general. Here, we summarize the current evidence related to angiography-based FFR and perspectives on future developments.

Recent Findings

Growing evidence suggests good diagnostic performance of angiography-based FFR measurements, both in chronic and acute coronary syndromes, as well as in specific lesion subsets, such as long and calcified lesions, left main coronary stenosis, and bifurcations. More recently, promising results on the superiority of angiography-based FFR as compared to angiography-guided PCI have been published.

Summary

Currently available angiography -FFR indices proved to be an excellent alternative to invasive pressure wire-based FFR. Dedicated prospective outcome data comparing these indices to routine guideline recommended PCI including the use of FFR are eagerly awaited.

Impact of the caFFR-Guided Functional SYNTAX Score on Ventricular Tachycardia/Fibrillation Development in Patients With Acute Myocardial Infarction

Aims

To explore the relationship between the severity of coronary artery disease (CAD) and the occurrence of ventricular tachycardia/ventricular fibrillation (VT/VF) in patients with acute myocardial infarction (AMI).

Methods

We retrospectively enrolled 705 patients with AMI, who were hospitalized and underwent percutaneous coronary intervention (PCI), in Nanfang Hospital from July 2017 to July 2020. Logistic regression analysis and backward stepwise approach were taken to select the correlation factors. The left and the receiver operating characteristic curves (ROC) analysis were plotted to observe the discriminative power of the SYNTAX score (SS)/caFFR-guided functional SS (FSScaFFR) on the incident VT/VF.

Results

About 58 (8.2%) patients experienced life-threatening VT/VF. The FSScaFFR (OR: 1.155; 95% CI: 1.047 to 1.273; p = 0.004) was an independent predictor of VT/VF after AMI. The ROC analysis showed that the discriminative power of FSScaFFR on the incident VT/VF was significantly better than SS (0.759 vs.0.695, p < 0.0001). Patients with VT/VF were categorized into 2 groups according to the interval between the onset of AMI and the VT/VF. The logistic regression analysis revealed that FSScaFFR was a significant independent correlation of early- and late-VT/VF.

Conclusion

The incident VT/VF in patients with AMI is closely associated with the severity of CAD evaluated by SS and FSScaFFR. Compared to SS, FSScaFFR has a higher correlation with VT/VF, and FSScaFFR was demonstrated to be an independent correlation factor of incident VT/VF after AMI.

Prognostic Value of Coronary Angiography-Derived Fractional Flow Reserve Immediately After Stenting

Objectives

The aim of this study was to investigate the potential prognostic value of post-percutaneous coronary intervention (PCI) angiography-derived fractional flow reserve (FFR) and its gradient across the stent.

Background

Post-PCI FFR and its gradient across the stent have been proved to be associated with clinical outcomes. However, little is known about the prognostic value of post-PCI coronary angiography-derived FFR and its gradient across the stent.

Methods

Patients diagnosed with coronary heart disease and participated in drug-eluting stent (DES) clinical trials for stent implantation in a single center were included for this retrospective analysis. A novel coronary angiography-derived FFR (caFFR) and its gradient across the stent were calculated offline using two projections from coronary angiography performed after PCI. Clinical follow-up was completed at 9 months after the index procedure and the primary outcome was target vessel failure (TVF), defined as a composite of target vessel-related myocardial infarction (MI), target vessel-related revascularization (TVR), and cardiac death. Coronary angiography was also performed at the 9 months follow-up time to get data of late lumen loss (LLL) and percent diameter stenosis (%DS).

Results

A total of 159 vessels in 136 patients were analyzed. The mean value of post-PCI caFFR was 0.90 ± 0.06. The median value of trans-stent caFFR gradient (ΔcaFFR_stent) was 0.04 (interquartile range 0.02-0.08). ΔcaFFR_stent>0 was demonstrated in 147 vessels (92.45%). The TVF rate was significantly higher in patients with post-PCI caFFR < 0.90 (4 [8.16%] vs. 1 [1.15%], P = 0.037), which was mainly achieved by the difference between the TVR rate. In the subgroup with lesions located in the left anterior descending coronary artery (LAD), post-PCI caFFR was an independent predictor of LLL (β = -1.07, 95% CI: -1.74 to -0.39, P = 0.002) and %DS at follow-up (β = -30.24, 95% CI: -56.44 to -4.04, P = 0.025), ΔcaFFR_stent was an independent predictor of LLL (β=0.98, 95% CI:0.13-1.83, P = 0.026).

Conclusion

Suboptimal post-PCI caFFR and trans-stent caFFR gradient were common among vessels immediately after stenting. Lower post-PCI caFFR was associated with a higher rate of 9-month TVF. After LAD PCI, both post-PCI caFFR and its gradient across stent were independent predictors of the neointimal proliferation of the target vessel evaluated by LLL and %DS at follow-up.

Diagnostic accuracy of CT-derived and angiogram-derived fractional flow reserve

AIMS

Although accumulating evidence demonstrated that virtual fractional flow reserve (FFR) based on coronary computed tomography angiography (CCTA) (CT-FFR) or invasive coronary angiogram (ICA) (CA-FFR) are promising alternatives to wire based FFR, which method has better diagnostic accuracy was still unclear. In our study, we aim to directly compare the diagnostic performance of CT-FFR and CA-FFR.

METHODS

During the period of September 2019 to December 2020, patients with at least one 30%-90% coronary artery stenosis were enrolled and received invasive FFR. Then, virtual FFR values were calculated based on both CCTA and ICA, and then compared with the invasive FFR value.

RESULTS

Invasive FFR measurements were successfully performed in 114 vessels of 96 patients. Both CT-FFR and CA-FFR showed good correlation with wire-based FFR, with r values of 0.84 and 0.71 respectively. In paired t-test, the deviation of CT-FFR and CA-FFR was not significantly different (t = -1.9083, p = 0.05889). In Bland-Altman analysis, the coefficients of variation were 8.4% and 13.2% for CT-FFR and CA-FFR respectively. In ROC curve analysis, the per-vessel diagnostic accuracy of CT-FFR and CA-FFR was 94.7% and 92.1% respectively. The area under the curve of CT-FFR was slightly higher than that of CA-FFR (0.986 and 0.916 respectively, the difference between areas = 0.070, 95% CI 0.003-0.137, p = 0.0227).

CONCLUSION

Both CT-FFR and CA-FFR had good diagnostic concordance with wire-based FFR. In ROC Curve analysis, CT-FFR demonstrated slightly higher diagnostic accuracy than CA-FFR.

CLINICAL TRIAL REGISTRATION

URL: https://www.chictr.org.cn/showproj.aspx?proj=44719. Unique Identifier: ChiCTR1900026971.