Functional assessment of coronary stenosis: an overview of available techniques. Is quantitative flow ratio a step to the future?

Clinical Outcomes of Surgical Revascularization Strategies Guided by Quantitative Flow Ratio in Primary Noncoronary Cardiac Surgery

PURPOSE

Information regarding quantitative flow ratio (QFR) usage in coronary artery bypass grafting (CABG) is lacking. We compared the incidence of postoperative long-term adverse cardiovascular and cerebrovascular events after QFR-guided or coronary angiography-guided adult cardiac surgery with concurrent bypass surgery.

MATERIALS AND METHODS

This study included 432 patients who underwent cardiopulmonary bypass (CPB) at our institution with at least 1 angiographical coronary artery lesion (diameter stenosis: 30% to 90%) between January 2015 and January 2016. The QFR of each patient was calculated. Patients who only underwent intraoperative coronary revascularization following the principles of optimal revascularization strategy were assigned to group A. Patients with coronary lesions not meeting the above criteria were placed in group B.

RESULTS

The average number of distal anastomoses of patients with combined CABG in group B was similar to that in Group A (1.9±1.0 vs. 1.7±0.9; P =0.081). Group A had a shorter CPB duration (114.4±49.2 vs 135.8±55.2 minutes; P <0.001) and shorter aortic cross-clamping time (83.6±36.2 vs 101.1±40.6 minutes; P <0.001). The rates of perioperative mortality and major complications did not differ between groups. Long-term major adverse cardiovascular and cerebrovascular events (MACCEs) were less common in group A than in group B (14.7% vs 29.5%; P <0.001).

CONCLUSIONS

In primary noncoronary cardiac surgery, despite the similar average numbers of distal anastomoses, the group with target vessels treated using an optimal coronary revascularization strategy presented shorter CPB time and aortic cross-clamping time than the other group. Multivariate analyses also showed a lower incidence of long-term MACCEs.

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.

The functional impact on donor vessel following transcatheter closure of coronary artery fistulas-a retrospective study using QFR analysis

Background

The impact of transcatheter closure of coronary artery fistula (CAF) and residual shunt after occlusion on improving blood flow in the donor vessel remains uncertain.

Objectives

To evaluate the functional impact on the donor vessel following CAFs closure using QFR (Quantitative Flow Ratio) analysis.

Methods

A total of 46 patients with 48 CAFs who underwent transcatheter closure at Shanghai Chest Hospital and Shuguang Hospital between March 2015 and August 2023 were included in the review. The clinical, angiographic details, and QFR data were subjected to analysis. The size of the fistulae was defined according to the ratio between the diameters of the fistulae and the largest diameter of the coronary vessel not feeding the coronary fistula.

Results

Among 48 CAFs, the average diameter of the fistulae ostium was 3.19 ± 1.04 mm, while the mean diameter of the donor vessel segment following fistulae was 3.45 ± 1.01 mm. The mean QFR value of the donor vessels with medium CAFs was found to be significantly lower than those with small CAFs (0.93 ± 0.10 vs. 0.98 ± 0.03; p < 0.05). Furthermore, the mean QFR value of donor vessels with medium CAFs was observed to be significantly improved after occlusion (0.99 ± 0.01 vs. 0.93 ± 0.10; p = 0.01). However, there was no statistical difference in the mean QFR value of donor vessels with small CAFs before and after occlusion (0.98 ± 0.03 vs. 0.98 ± 0.02; p > 0.05). Moreover, the changes in QFR were more pronounced in donor vessels with medium CAFs compared to those with small CAFs after occlusion (0.06 ± 0.10 vs. 0.005 ± 0.012; p = 0.01). There is no statistical difference in the mean QFR variation and QFR variation rate between donor vessels with CAFs that occurred residual shunt and those without residual shunt after occlusion (p > 0.05).

Conclusions

The presence of medium CAFs has a significant impact on the blood flow of the donor vessel, as compared to small CAFs, and may benefit from occlusion. A small residual shunt has no significant impact on the effectiveness of CAFs occlusion in enhancing donor blood flow.

Diagnostic performance of the quantitative flow ratio and CT-FFR for coronary lesion-specific ischemia

Fractional flow reserve (FFR) has become the gold standard for evaluating coronary lesion-specific ischemia. However, FFR is an invasive method that may cause possible complications in the coronary artery and requires expensive equipment, which limits its use. Promising noninvasive diagnostic methods, such as computed tomography angiography-derived FFR (CT-FFR) and the quantitative flow ratio (QFR), have been proposed. In this study, we evaluated the diagnostic performance of the QFR and CT-FFR in predicting coronary lesion-specific ischemia, with the FFR serving as the reference standard. Patients with suspected or known coronary artery disease who underwent coronary CT angiography revealing 30-90% diameter stenosis in the main coronary artery (≥ 2.0 mm reference diameter) were enrolled. The FFR was measured during invasive coronary angiography (within 15 days after coronary CT angiography). An FFR ≤ 0.8 was the reference standard for coronary lesion-specific ischemia. A total of 103 vessels from 92 consecutive patients (aged 59.8 ± 9.2 years; 60.9% were men) were evaluated. The diagnostic performance of a QFR ≤ 0.80 for predicting coronary lesion-specific ischemia demonstrated good diagnostic accuracy, sensitivity, and specificity (92.2%, 87.2%, and 96.4%, respectively), with an area under the receiver operating characteristic curve (AUC) of 0.987 (P < 0.0001). The diagnostic performance of a CT-FFR ≤ 0.80 for predicting coronary lesion-specific ischemia also demonstrated good diagnostic accuracy, sensitivity, and specificity (96.1%, 95.7%, and 96.4%, respectively), with an AUC of 0.967 (P < 0.0001). However, there was no significant difference in the AUC between a QFR ≤ 0.80 and a CT-FFR ≤ 0.80 for predicting coronary lesion-specific ischemia (P = 0.319). There was an excellent correlation between the QFR and FFR (r = 0.856, P < 0.0001). The CT-FFR and FFR also showed a good direct correlation (r = 0.816, P < 0.0001). The QFR and CT-FFR are strongly correlated with the FFR and can provide excellent clinical diagnostic performance for coronary lesion-specific ischemia detection.

Predictors of long-term adverse outcomes after successful chronic total occlusion intervention: physiology or morphology?

BACKGROUND

Quantitative flow ratio (QFR) and target-vessel SYNTAX score (tvSS) are novel indices used to assess lesion physiology and morphology in percutaneous coronary intervention (PCI). Their prognostic implication after successful recanalization of coronary chronic total occlusion (CTO) is unknown.

OBJECTIVES

To investigate the prognostic value of QFR measured immediately after successful CTO-recanalization in predicting vessel-oriented adverse events, and to compare it with the pre-procedural morphological tvSS.

METHODS

QFR was measured offline after successful CTO-PCIs in a single center. We grouped the patients according to a cut-off value of post-PCI QFR (0.91). The primary outcome was target-vessel failure (TVF) at 2 years.

RESULTS

Among 470 CTO lesions performed during the study period, 324 were eligible for QFR analysis (258 with QFR ≥ 0.91 and 66 with QFR < 0.91). The mean age of the study population was 68.3 ± 10.7 years. The low QFR group had a lower left ventricular ejection fraction (45.8 ± 13.9% vs. 49.8 ± 12.4%, p = 0.025) and a higher rate of atrial fibrillation (19.7% vs. 11.2%, p = 0.020). The mean tvSS was 12.8 ± 4.8, and it showed no significant difference in both groups (13.6 ± 5.1 vs. 12.6 ± 4.6, p = 0.122). Patients with low post-CTO QFR had a trend to develop more TVF at 2 years (21.2% vs. 12.4%, HR 1.74; 95% CI 0.93-3.25, p = 0.086). Low post-CTO QFR failed to predict 2-year TVF (aHR 1.67; 95% CI 0.85-3.29, p = 0.136), while pre-procedural tvSS was an independent predictor for 2-year TVF (aHR 1.06; 95% CI 1.01-1.13, p = 0.030).

CONCLUSION

We found a limited prognostic value of immediate physiological assessment using QFR after successful CTO intervention. Pre-procedure morphological characteristics of CTO lesions using tvSS can play a role in predicting long-term adverse events.

QFR for the Revascularization of Nonculprit Vessels in MI Patients: Insights From the FIRE Trial

BACKGROUND

The role of quantitative flow ratio (QFR) in the treatment of nonculprit vessels of patients with myocardial infarction (MI) is a topic of ongoing discussion.

OBJECTIVES

This study aimed to investigate the predictive capability of QFR for adverse events and its noninferiority compared to wire-based functional assessment in nonculprit vessels of MI patients.

METHODS

The FIRE (Functional Assessment in Elderly MI Patients With Multivessel Disease) trial randomized 1,445 older MI patients to culprit-only (n = 725) or physiology-guided complete revascularization (n = 720). In the culprit-only arm, angiographic projections of nonculprit vessels were prospectively collected, centrally reviewed for QFR computation, and associated with endpoints. In the complete revascularization arm, endpoints were compared between nonculprit vessels investigated with QFR or wire-based functional assessment. The primary endpoint was the vessel-oriented composite endpoint (VOCE) at 1 year.

RESULTS

QFR was measured on 903 nonculprit vessels from 685 patients in the culprit-only arm. Overall, 366 (40.5%) nonculprit vessels showed a QFR value ≤0.80, with a significantly higher incidence of VOCEs (22.1% vs 7.1%; P < 0.001). QFR ≤0.80 emerged as an independent predictor of VOCEs (HR: 2.79; 95% CI: 1.64-4.75). In the complete arm, QFR was used in 320 (35.2%) nonculprit vessels to guide revascularization. When compared with propensity-matched nonculprit vessels in which treatment was guided by wire-based functional assessment, no significant difference was observed (HR: 0.57; 95% CI: 0.28-1.15) in VOCEs.

CONCLUSIONS

This prespecified subanalysis of the FIRE trial provides evidence supporting the safety and efficacy of QFR-guided interventions for the treatment of nonculprit vessels in MI patients. (Functional Assessment in Elderly MI Patients With Multivessel Disease [FIRE]; NCT03772743).

Sex Differences in Clinical Outcomes Associated With Quantitative Flow Ratio-Guided Percutaneous Coronary Intervention

Background

FAVOR III China (Comparison of Quantitative Flow Ratio Guided and Angiography Guided Percutaneous Intervention in Patients with Coronary Artery Disease) reported improved clinical outcomes in quantitative flow ratio (QFR) relative to angiography-guided percutaneous coronary intervention (PCI), but the clinical impact of QFR-guided PCI according to sex remains unknown.

Objectives

The authors sought to compare sex differences in the 2-year clinical benefits of a QFR-guided PCI strategy and to evaluate the differences in outcomes between men and women undergoing contemporary PCI.

Methods

This study involved a prespecified subgroup analysis of the FAVOR III China trial, in which women and men were randomized to a QFR-guided strategy or a standard angiography-guided strategy. Sex differences in clinical benefit of the QFR guidance were analyzed for major adverse cardiac events (MACE), a composite of all-cause death, myocardial infarction, or ischemia-driven revascularization within 2 years.

Results

A total of 1,126 women and 2,699 men were eligible and the occurrence of 2-year MACE was similar between women and men (10.3% vs 10.5%; P = 0.96). Compared with an angiography-guided strategy, a QFR-guided strategy resulted in a 7.9% and 9.7% reduction in PCI rates in men and women, respectively. A QFR-guided strategy resulted in similar relative risk reductions for 2-year MACE in women (8.0% vs 12.7%; HR: 0.62; 95% CI: 0.42-0.90) and men (8.7% vs 12.4%; HR: 0.69; 95% CI: 0.54-0.87) (Pinteraction = 0.61). Furthermore, QFR values were not significantly different between men and women with various angiographic stenosis categories.

Conclusions

A QFR-guided PCI strategy resulted in improved MACE in both men and women at 2 years compared with an angiography-guided PCI strategy. The FAVOR III China Study [FAVOR III China]; (NCT03656848).

The Differences of Quantitative Flow Ratio in Coronary Artery Stenosis with or without Atrial Fibrillation

Quantitative flow ratio (QFR) is a new method for the assessment of the extent of coronary artery stenosis. But it may be obscured by the cardiac remodeling and abnormal blood flow of the coronary artery when encountering atrial fibrillation (AF). The present study aimed to examine the impact of these changed structures and blood flow of coronary arteries on QFR results in AF patients. Methods and Results. We evaluated QFR in 223 patients (112 patients with AF; 111 non-AF patients served as controls) who had undergone percutaneous coronary intervention (PCI) due to severe stenoses in coronary arteries. QFR of the target coronary was determined according to the flow rate of the contrast agent. Results showed that AF patients had significantly higher QFR values than control (0.792 ± 0.118 vs. 0.685 ± 0.167, p < 0.001). We further analyzed local QFR around the stenoses (0.858 ± 0.304 vs. 0.756 ± 0.146, p=0.002), residual QFR (0.958 ± 0.055 vs. 0.929 ± 0.093, p=0.005), and index QFR (0.807 ± 0.108 vs. 0.713 ± 0.152, p < 0.001) in these two groups of patients with and without AF. Further analysis revealed that QFR in AF patients was negatively correlated with coronary flow velocity (R = -0.22, p=0.02) and area of stenosis (R = -0.70, p < 0.001) but positively correlated with the minimum lumen area (MLA) (R = 0.47, p < 0.001). Conclusion. AF patients with coronary artery stenosis have higher QFR values, which are associated with decreased blood flow velocity, smaller stenosis, and larger MLA in AF patients upon cardiac remodeling.

A novel method for noninvasive quantification of fractional flow reserve based on the custom function

Boundary condition settings are key risk factors for the accuracy of noninvasive quantification of fractional flow reserve (FFR) based on computed tomography angiography (i.e., FFRCT). However, transient numerical simulation-based FFRCT often ignores the three-dimensional (3D) model of coronary artery and clinical statistics of hyperemia state set by boundary conditions, resulting in insufficient computational accuracy and high computational cost. Therefore, it is necessary to develop the custom function that combines the 3D model of the coronary artery and clinical statistics of hyperemia state for boundary condition setting, to accurately and quickly quantify FFRCT under steady-state numerical simulations. The 3D model of the coronary artery was reconstructed by patient computed tomography angiography (CTA), and coronary resting flow was determined from the volume and diameter of the 3D model. Then, we developed the custom function that took into account the interaction of stenotic resistance, microcirculation resistance, inlet aortic pressure, and clinical statistics of resting to hyperemia state due to the effect of adenosine on boundary condition settings, to accurately and rapidly identify coronary blood flow for quantification of FFRCT calculation (FFRU). We tested the diagnostic accuracy of FFRU calculation by comparing it with the existing methods (CTA, coronary angiography (QCA), and diameter-flow method for calculating FFR (FFRD)) based on invasive FFR of 86 vessels in 73 patients. The average computational time for FFRU calculation was greatly reduced from 1-4 h for transient numerical simulations to 5 min per simulation, which was 2-fold less than the FFRD method. According to the results of the Bland-Altman analysis, the consistency between FFRU and invasive FFR of 86 vessels was better than that of FFRD. The area under the receiver operating characteristic curve (AUC) for CTA, QCA, FFRD and FFRU at the lesion level were 0.62 (95% CI: 0.51-0.74), 0.67 (95% CI: 0.56-0.79), 0.85 (95% CI: 0.76-0.94), and 0.93 (95% CI: 0.87-0.98), respectively. At the patient level, the AUC was 0.61 (95% CI: 0.48-0.74) for CTA, 0.65 (95% CI: 0.53-0.77) for QCA, 0.83 (95% CI: 0.74-0.92) for FFRD, and 0.92 (95% CI: 0.89-0.96) for FFRU. The proposed novel method might accurately and rapidly identify coronary blood flow, significantly improve the accuracy of FFRCT calculation, and support its wide application as a diagnostic indicator in clinical practice.

Accuracy of the angiography-based quantitative flow ratio in intermediate left main coronary artery lesions and comparison with visual estimation

BACKGROUND

Revascularization of left main coronary artery (LMCA) stenosis is mostly based on angiography. Indices based on angiography might increase accuracy of the decision, although they have been scarcely used in LMCA. The objective of this study is to study the diagnostic agreement of QFR (quantitative flow ratio) with wire-based fractional flow reserve (FFR) in LMCA lesions and to compare with visual severity assessment.

METHODS

In a series of patients with invasive FFR assessment of intermediate LMCA stenoses we retrospectively compared the measured value of QFR with that of FFR and the estimate of significance from angiography.

RESULTS

107 QFR studies were included. The QFR intra-observer and inter-observer agreement was 87% and 82% respectively. The mean QFR-FFR difference was 0.047 ± 0.05 with a concordance of 90.7%, sensitivity 88.1%, specificity 92.3%, positive predictive value 88.1% and negative predictive value 92.3%. All these values were superior to those observed with the visual estimation which showed an intra- and inter-observer agreement of 73% and 72% respectively, besides 78% with the FFR value. The low diagnostic performance of the visual estimation and the acceptable performance of the QFR index measurement were observed in all subgroups analysed.

CONCLUSIONS

QFR allows an acceptable estimate of the FFR obtained with intracoronary pressure guidewire in intermediate LMCA lesions, and clearly superior to the assessment based on angiography alone. The decision to revascularize patients with moderate LMCA lesions should not be based solely on the degree of angiographic stenosis.

Coronary Physiology: Modern Concepts for the Guidance of Percutaneous Coronary Interventions and Medical Therapy

Recent evidence on ischemia, rather than coronary artery disease (CAD), representing a major determinant of outcomes, has led to a progressive shift in the management of patients with ischemic heart disease. According to most recent guidelines, myocardial revascularization strategies based on anatomical findings should be progressively abandoned in favor of functional criteria for the guidance of PCI. Thus, emerging importance has been assigned to the assessment of coronary physiology in order to determine the ischemic significance of coronary stenoses. However, despite several indexes and tools that have been developed so far, the existence of technical and clinical conditions potentially biasing the functional evaluation of the coronary tree still cause debates regarding the strategy of choice. The present review provides an overview of the available methods and the most recent acquirements for the invasive assessment of ischemia, focusing on the most widely available indexes, fractional flow reserve (FFR) and instant-wave free ratio (iFR), in addition to emerging examples, as new approaches to coronary flow reserve (CFR) and microvascular resistance, aiming at promoting the knowledge and application of those "full physiology" principles, which are generally advocated to allow a tailored treatment and the achievement of the largest prognostic benefits.

Physiologic Lesion Assessment to Optimize Multivessel Disease

PURPOSE OF REVIEW

Multivessel coronary artery disease, defined as significant stenosis in two or more major coronary arteries, is associated with high morbidity and mortality. The diagnosis and treatment of multivessel disease have evolved in the PCI era from solely a visual estimation of ischemic risk to a functional evaluation during angiography. This review summarizes the evidence and discusses the commonly used methods of multivessel coronary artery stenosis physiologic assessment.

RECENT FINDINGS

While FFR remains the gold standard in coronary physiologic assessment, several pressure-wire-based non-hyperemic indices of functional stenosis have been developed and validated as well as wire-free angiographically derived quantitative flow ratio. Identifying and treating functionally significant coronary atherosclerotic lesions reduce symptoms and major adverse cardiovascular events. Coronary physiologic assessment in multivessel disease minimizes the observer bias in visual estimates of stenosis, changes clinical management, and improves patient outcomes.

Impact of diabetes on coronary physiology evaluated by quantitative flow ratio in patients who underwent percutaneous coronary intervention

Aims/Introduction

There are mixed opinions on the influence of diabetes on the prognosis of patients receiving percutaneous coronary intervention (PCI). Therefore, in this study, the quantitative flow ratio (QFR), an emerging technology of functional evaluation, was used to explore the impact of diabetes on coronary physiology in patients who underwent PCI.

Materials and Methods

Patients who underwent successful PCI and a 1‐year angiographic follow up were retrospectively screened and analyzed by the QFR. Based on the presence or absence of diabetes, 677 enrolled patients (794 vessels) were classified into a diabetes group (211 patients, 261 vessels) and a non‐diabetes group (466 patients, 533 vessels). The results of QFR analysis and clinical outcomes were compared between the two groups.

Results

The two groups reached a similar level of post‐PCI QFR (0.95 ± 0.09 vs 0.96 ± 0.06, P = 0.292). However, at the 1‐year follow up, the QFR was lower (0.93 ± 0.11 vs 0.96 ± 0.07, P < 0.001), and the degree of QFR decline was more obvious (−0.024 ± 0.090 vs −0.008 ± 0.070, P = 0.023) in the diabetes group. Additionally, diabetes was independently associated with functional restenosis (odds ratio 2.164, 95% confidence interval 1.210–3.870, P = 0.009) and target vessel failure (odds ratio 2.654, 95% confidence interval 1.405–5.012, P = 0.003).

Conclusion

As evaluated by the QFR, patients with diabetes received less coronary physiological benefit from PCI, which was consistent with their clinical outcomes.

Functional Coronary Artery Assessment: a Systematic Literature Review

Cardiovascular diseases represent the number one cause of death in the world, including the most common disorders in the heart's health, namely coronary artery disease (CAD). CAD is mainly caused by fat accumulated in the arteries' internal walls, creating an atherosclerotic plaque that impacts the blood flow functional behavior. Anatomical plaque characteristics are essential but not sufficient for a complete functional assessment of CAD. In fact, plaque analysis and visual inspection alone have proven insufficient to determine the lesion severity and hemodynamic repercussion. Furthermore, the fractional flow reserve (FFR) exam, which is considered the gold standard for stenosis functional impair determination, is invasive and contains several limitations. Such a panorama evidences the need for new techniques applied to image exams to improve CAD functional assessment. In this article, we perform a systematic literature review on emerging methods determining CAD significance, thus delivering a unique base for comparing these methods, qualitatively and quantitatively. Our goal is to guide further studies with evidence from the most promising methods, highlighting the benefits from both areas. We summarize benchmarks, metrics for evaluation, and challenges already faced, thus shedding light on the requirements for a valid, meaningful, and accepted technique for functional assessment evaluation. We create a base of comparison based on quantitative and qualitative indicators and highlight the most relevant geometrical metrics that correlate with lesion significance. Finally, we point out future benchmarks based on recent literature.

Evaluation of the Safety and Efficacy of Coronary Intravascular Lithotripsy for Treatment of Severely Calcified Coronary Stenoses: Evidence From the Serial Disrupt CAD Trials

Background: Previous understanding holds that rotational atherectomy and modified balloons remain the default strategy for severely calcified coronary stenoses. In recent years, coronary intravascular lithotripsy (IVL) provides new ideas. This study was conducted to evaluate the safety and efficacy of IVL for the treatment of severely calcified coronary stenoses. Methods: The serial Disrupt CAD trials (Disrupt CAD I, Disrupt CAD II, Disrupt CAD III, and Disrupt CAD IV) were included in this study. The safety endpoint was freedom from major adverse cardiovascular events (MACE) in hospital, at 30 days, and at 6 months following the index procedure. The efficacy endpoints included procedural success and angiographic success. Optical coherence tomography (OCT) was used to evaluate the mechanism of action of IVL quantifying the coronary artery calcification (CAC) characteristics and calcium plaque fracture. Results: We enrolled a total of 628 patients with a mean age of 71.8 years, 77.1% males. In these patients, the left anterior descending artery and right coronary artery were the most vulnerable vessels. The diameter stenosis was 64.6 ± 11.6% and the lesion length was 24.2 ± 11.4 mm. IVL had a favorable efficacy (93.0% procedural success, 97.5% angiographic success, and 100.0% stent delivery). Among the 628 patients, 568, 568, and 60 reported MACE endpoints in hospital, at 30 days, and at 6 months, respectively. The results showed that 528, 514, and 55 patients were free from MACE in hospital, at 30 days, and at 6 months, respectively. OCT measurements demonstrated that calcium fracture was the underlying mechanism of action for coronary IVL. Conclusions: IVL is safe and efficient for severely calcified coronary stenoses, and, importantly, calcium fracture facilitated increased vessel compliance and favorable stent expansion.

Branch flow distribution approach and its application in the calculation of fractional flow reserve in stenotic coronary artery

OBJECTIVE

To calculate fractional flow reserve (FFR) based on computed tomography angiography (i.e., FFRCT) by considering the branch flow distribution in the coronary arteries.

BACKGROUND

FFR is the gold standard to diagnose myocardial ischemia caused by coronary stenosis. An accurate and noninvasive method for obtaining total coronary blood flow is needed for the calculation of FFRCT.

METHODS

A mathematical model for estimating the coronary blood flow rate and two approaches for setting the patient-specific flow boundary condition were proposed. Coronary branch flow distribution methods based on a volume-flow approach and a diameter-flow approach were employed for the numerical simulation of FFRCT. The values of simulated FFRCT for 16 patients were compared with their clinically measured FFR.

RESULTS

The ratio of total coronary blood flow to cardiac output and the myocardial blood flow under the condition of hyperemia were 16.97% and 4.07 mL/min/g, respectively. The errors of FFRCT compared with clinical data under the volume-flow approach and diameter-flow approach were 10.47% and 11.76%, respectively, the diagnostic accuracies of FFRCT were 65% and 85%, and the consistencies were 95% and 90%.

CONCLUSIONS

The mathematical model for estimating the coronary blood flow rate and the coronary branch flow distribution method can be applied to calculate the value of clinical noninvasive FFRCT.

Physiologic Assessment of Coronary Stenosis: Current Status and Future Directions

PURPOSE OF REVIEW

Percutaneous coronary intervention (PCI) is a commonly used treatment option in coronary artery disease (CAD). Reduced major adverse cardiovascular events (MACE) in those randomized to PCI compared to optimal medical therapy have been demonstrated only if it is performed for physiologically significant coronary lesions. Despite data demonstrating improved outcomes primarily in stable CAD and then acute settings, physiology-guided PCI remains underutilized. This review summarizes the evidence and commonly used methods for physiologic assessment of coronary stenosis.

RECENT FINDINGS

Fractional flow reserve (FFR) is the gold standard for the analysis of lesion severity. Its use is limited by the need for adenosine, which adds time, complexity, and potential adverse effects. Non-hyperemic instantaneous wave-free ratio-guided revascularization and quantitative flow reserve ratio assessment both have shown safety and effectiveness with improved patient outcomes. Coronary physiological assessment solves the ambiguity of coronary angiography. Detecting physiologically significant stenoses is crucial to decide which lesion needs to be treated. Technological advances have led to the development of new assessment indices in addition to FFR.

Future culprit detection based on angiography-derived FFR

OBJECTIVES

We sought to characterize the hemodynamic impact of mild coronary artery disease (CAD) using quantitative flow ratio (QFR, an angiography-derived fractional flow reserve [FFR]) in a population of patients with only non-significant CAD at baseline that subsequently experienced a myocardial infarction (MI).

BACKGROUND

The discriminatory value of FFR in patients with mild CAD remains imperfect.

METHODS

We retrospectively included patients who underwent invasive coronary angiography for an MI, in whom another angiogram had been performed within the previous 5 years. Three-dimensional quantitative coronary angiography, QFR, and lesion length analysis were conducted on lesions responsible for the MI (future culprit lesions, [FCL]) as well as on control lesions (non-culprit lesions, [NCL]).

RESULTS

Eighty-three FCL and 117 NCL were analyzed in 83 patients: FCL were more severe (median % diameter of stenosis [DS] 39.1% [29.8; 45.7] vs. 29.8% [25.0; 37.2], p < .001), had lower QFR values (0.94 [0.86; 0.98] vs. 0.98 [0.96; 1.00], p < .001) and tended to be longer (15.2 mm [10.0; 27.3] vs. 12.7 mm [9.3; 22.4], p = .070) than NCL. In lesions with an interval < 2 years between baseline angiography and MI, the difference in QFR was more pronounced compared to the lesions with a longer interval (FCL: 0.92 [0.85; 0.97] vs. NCL: 0.98 [0.94; 1.00], p < .001 and FCL: 0.96 [0.88; 1.00] vs. NCL: 0.98 [0.96;1.00], p = .006 respectively) CONCLUSION: Mild coronary stenoses that are subsequently responsible for an MI (FCL) exhibit a higher DS and lower QFR years before the event. Furthermore, FCL with a lower QFR at baseline appear to lead earlier to MI.

Quantitative flow ratio as a new tool for angiography-based physiological evaluation of coronary artery disease: a review

The functional evaluation of coronary stenoses has obtained important clinical results in recent years, resulting in strong guideline recommendations. Nonetheless, the use of coronary wire-based functional evaluation has not yet become part of the routine in catheterization laboratories for several reasons, including the need to advance a wire into the coronary vessel to interrogate the stenosis. Angiography-derived indexes have been introduced to expand the current use of physiology to estimate the functional meaning of a stenosis on the basis of angiographic data only. The most studied and validated angiography-derived index is certainly the quantitative flow ratio. This article will summarize the basics of the quantitative flow ratio, the related validation studies and its current and future applications.

Coronary Revascularization and Long-Term Survivorship in Chronic Coronary Syndrome

Ischemic heart disease (IHD) persists as the leading cause of death in the Western world. In recent decades, great headway has been made in reducing mortality due to IHD, based around secondary prevention. The advent of coronary revascularization techniques, first coronary artery bypass grafting (CABG) surgery in the 1960s and then percutaneous coronary intervention (PCI) in the 1970s, has represented one of the major breakthroughs in medicine during the last century. The benefit provided by these techniques, especially PCI, has been crucial in lowering mortality rates in acute coronary syndrome (ACS). However, in the setting where IHD is most prevalent, namely chronic coronary syndrome (CCS), the increase in life expectancy provided by coronary revascularization is controversial. Over more than 40 years, several clinical trials have been carried out comparing optimal medical treatment (OMT) alone with a strategy of routine coronary revascularization on top of OMT. Beyond a certain degree of symptomatic improvement and lower incidence of minor events, routine invasive management has not demonstrated a convincing effect in terms of reducing mortality in CCS. Based on the accumulated evidence more than half a century after the first revascularization procedures were used, invasive management should be considered in those patients with uncontrolled symptoms despite OMT or high-risk features related to left ventricular function, coronary anatomy, or functional assessment, taking into account the patient expectations and preferences.

A case of mild-to-intermediate left-main lesion with high-risk plaque features: "Blindness of physiology" for PCI guidance?

In patients presenting with acute coronary syndrome without ST elevation, both FFR and OCT imaging may be necessary to adequately interrogate patients with intermediate and ambiguous left-main coronary stenosis.

Quantitative flow ratio-guided strategy versus angiography-guided strategy for percutaneous coronary intervention: Rationale and design of the FAVOR III China trial

BACKGROUND

Quantitative flow ratio (QFR) is a novel angiography-based approach enabling fast computation of fractional flow reserve without use of pressure wire or adenosine. The objective of this investigator-initiated, multicenter, patient- and clinical assessor-blinded randomized trial is to evaluate the efficacy and cost-effectiveness of a QFR-augmented angiography-guided (QFR-guided) strategy versus an angiography-only guided (angiography-guided) strategy for percutaneous coronary intervention (PCI) in patients with coronary artery disease.

METHODS

Approximately 3,830 patients will be randomized in a 1:1 ratio to a QFR-guided or an angiography-guided strategy. Included subjects scheduled for coronary angiography have at least 1 lesion eligible for PCI with 50%-90% stenosis in an artery with ≥2.5 mm reference diameter. Subjects assigned to the QFR-guided strategy will have QFR measured in each interrogated vessel and undergo PCI when QFR ≤0.80, with deferral for lesions with QFR >0.80. Those assigned to the angiography-guided strategy will undergo PCI based on angiography. Optimal medical therapy will be administered to all treated and deferred patients. The primary end point is the 1-year rate of major adverse cardiac events (MACE), a composite of all-cause mortality, any myocardial infarction, or any ischemia-driven revascularization. The major secondary end point is 1-year MACE excluding periprocedural myocardial infarction. Other secondary end points include the individual components of MACE and cost-effectiveness end points. The sample size affords 85% power to demonstrate superiority of QFR guidance compared with angiography guidance.

CONCLUSIONS

The FAVOR III China study will be the first randomized trial to examine the effectiveness and cost-effectiveness of a QFR-guided versus an angiography-guided PCI strategy in coronary artery disease patients.

Transradial access versus transfemoral access: a comparison of outcomes and efficacy in reducing hemorrhagic events

Introduction: The radial artery is currently the most widely used access site for PCI procedures both acute and stable patient settings. Thanks to advantages in pharmacological therapy as well as in interventional devices, the rate of ischemic complications following PCI has significantly decreased. Nevertheless, this has been counterbalanced by an increased risk of periprocedural and late bleeding event, that can occur both at access and non-access sites. Choice of access site for PCI is of paramount importance to reduce the risk of access-related bleeding events. Areas covered: The aim of this review is to provide an overview of the actual available evidence comparing the transradial versus transfemoral approach to reduce hemorrhagic events. The most robust evidence comes from large randomized trials, partly also from observational registries, which compared the transradial and transfemoral approach. Expert opinion: Results show that radial access has proved to be decisive in reducing the incidence of hemorrhagic events. Furthermore, it showed a significant reduction in mortality and AKI compared to transfemoral access. However, increased experience in the use of the radial approach has led to less practice in the use of the femoral approach, which may be useful in cases of emergency, complications or inability to use the radial artery.