Optical flow ratio for assessing stenting result and physiological significance of residual disease

Illusion of revascularization: does anyone achieve optimal revascularization during percutaneous coronary intervention?

This Perspective article is a form of 'pastiche', inspired by the 1993 review by Lincoff and Topol entitled 'Illusion of reperfusion', and explores how their concept continues to apply to percutaneous revascularization in patients with coronary artery disease and ischaemia. Just as Lincoff and Topol argued that reperfusion of acute myocardial infarction was facing unresolved obstacles that hampered clinical success in 1993, we propose that challenging issues are similarly jeopardizing the potential benefits of stent-based angioplasty today. By analysing the appropriateness and efficacy of percutaneous coronary intervention (PCI), we emphasize the limitations of relying solely on visual angiographic guidance, which frequently leads to inappropriate stenting and overtreatment in up to one-third of patients and the associated increased risk of periprocedural myocardial infarction. The lack of optimal revascularization observed in half of patients undergoing PCI confers risks such as suboptimal physiology after PCI, residual angina and long-term stent-related events, leaving an estimated 76% of patients with an 'illusion of revascularization'. These outcomes highlight the need to refine our diagnostic tools by integrating physiological assessments with targeted intracoronary imaging and emerging strategies, such as co-registration systems and angiography-based computational methods enhanced by artificial intelligence, to achieve optimal revascularization outcomes.

Prognostic value of optical flow ratio for cardiovascular outcomes in patients after percutaneous coronary stent implantation

Background

The relationship between the optical flow ratio (OFR) and clinical outcomes in patients with coronary artery disease (CAD) after percutaneous coronary stent implantation (PCI) remains unknown.

Objective

To examine the correlation between post-PCI OFR and clinical outcomes in patients with CAD following PCI.

Methods

Patients who underwent optical coherence tomography (OCT) guided PCI at Guangdong Provincial People's Hospital were retrospectively and continuously enrolled. Clinical data, post-PCI OCT characteristics, and OFR measurements were collected and analyzed to identify predictors of target vessel failure (TVF) after PCI.

Results

Among 354 enrolled patients, 26 suffered TVF during a median follow-up of 484 (IQR: 400-774) days. Post-PCI OFR was significantly lower in the TVF group than in the non-TVF group (0.89 vs. 0.93; P = 0.001). In multivariable Cox regression analysis, post-PCI OFR (HR per 0.1 increase: 0.60; 95% CI: 0.41-0.89; P = 0.011), large stent edge dissection (HR: 3.85; 95% CI: 1.51-9.84; P = 0.005) and thin-cap fibroatheroma (TCFA) (HR: 2.95; 95% CI: 1.19-7.35; P = 0.020) in the non-stented segment were independently associated with TVF. In addition, the inclusion of post-PCI OFR to baseline characteristics and post-PCI OCT findings improved the predictive power of the model to distinguish subsequent TVF after PCI (0.838 vs. 0.796; P = 0.028).

Conclusion

The post-PCI OFR serves as an independent determinant of risk for TVF in individuals with CAD after PCI. The inclusion of post-PCI OFR assessments, alongside baseline characteristics and post-PCI OCT findings, substantially enhances the capacity to differentiate the subsequent manifestation of TVF in CAD patients following PCI.

Management strategies for heavily calcified coronary stenoses: an EAPCI clinical consensus statement in collaboration with the EURO4C-PCR group

Since the publication of the 2015 EAPCI consensus on rotational atherectomy, the number of percutaneous coronary interventions (PCI) performed in patients with severely calcified coronary artery disease has grown substantially. This has been prompted on one side by the clinical demand for the continuous increase in life expectancy, the sustained expansion of the primary PCI networks worldwide, and the routine performance of revascularization procedures in elderly patients; on the other side, the availability of new and dedicated technologies such as orbital atherectomy and intravascular lithotripsy, as well as the optimization of the rotational atherectomy system, has increased operators' confidence in attempting more challenging PCI. This current EAPCI clinical consensus statement prepared in collaboration with the EURO4C-PCR group describes the comprehensive management of patients with heavily calcified coronary stenoses, starting with how to use non-invasive and invasive imaging to assess calcium burden and inform procedural planning. Objective and practical guidance is provided on the selection of the optimal interventional tool and technique based on the specific calcium morphology and anatomic location. Finally, the specific clinical implications of treating these patients are considered, including the prevention and management of complications and the importance of adequate training and education.

Practical Application of Coronary Physiologic Assessment: Asia-Pacific Expert Consensus Document: Part 1

Coronary physiologic assessment is performed to measure coronary pressure, flow, and resistance or their surrogates to enable the selection of appropriate management strategy and its optimization for patients with coronary artery disease. The value of physiologic assessment is supported by a large body of evidence that has led to major recommendations in clinical practice guidelines. This expert consensus document aims to convey practical and balanced recommendations and future perspectives for coronary physiologic assessment for physicians and patients in the Asia-Pacific region based on updated information in the field that including both wire- and image-based physiologic assessment. This is Part 1 of the whole consensus document, which describes the general concept of coronary physiology, as well as practical information on the clinical application of physiologic indices and novel image-based physiologic assessment.

Machine-learning-based prediction of fractional flow reserve after percutaneous coronary intervention

BACKGROUND AND AIMS

Post-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) reflects residual atherosclerotic burden and is associated with future events. How much post-PCI FFR can be predicted based on baseline basic information and the clinical relevance have not been investigated.

METHODS

We compiled a multicenter registry of patients undergoing pre- and post-PCI FFR. Machine-learning (ML) algorithms were designed to predict post-PCI FFR levels from baseline demographics, quantitative coronary angiography, and pre-PCI FFR. FFR deviation was defined as actual minus ML-predicted post-PCI FFR levels, and its association with incident target vessel failure (TVF) was evaluated.

RESULTS

Median (IQR) pre- and post-PCI FFR values were 0.71 (0.61, 0.77) and 0.88 (0.84, 0.93), respectively. The Spearman correlation coefficient of the actual and predicted post-PCI FFR was 0.54 (95% CI: 0.52, 0.57). FFR deviation was non-linearly associated with incident TVF (HR [95% CI] with Q3 as reference: 1.65 [1.14, 2.39] in Q1, 1.42 [0.98, 2.08] in Q2, 0.81 [0.53, 1.26] in Q4, and 1.04 [0.69, 1.56] in Q5). A model with polynomial function of continuous FFR deviation indicated increasing TVF risk for FFR deviation ≤0 but plateau risk with FFR deviation >0.

CONCLUSIONS

An ML-based algorithm using baseline data moderately predicted post-PCI FFR. The deviation of post-PCI FFR from the predicted value was associated with higher vessel-oriented event.

Diagnostic accuracy of optical flow ratio: an individual patient-data meta-analysis

BACKGROUND

Optical flow ratio (OFR) is a novel method for the fast computation of fractional flow reserve (FFR) from optical coherence tomography.

AIMS

We aimed to evaluate the diagnostic accuracy of OFR in assessing intermediate coronary stenosis using wire-based FFR as the reference.

METHODS

We performed an individual patient-level meta-analysis of all available studies with paired OFR and FFR assessments. The primary outcome was vessel-level diagnostic concordance of the OFR and FFR, using a cut-off of ≤0.80 to define ischaemia and ≤0.90 to define suboptimal post-percutaneous coronary intervention (PCI) physiology. This meta-analysis was registered in PROSPERO (CRD42021287726).

RESULTS

Five studies were finally included, providing 574 patients and 626 vessels (404 pre-PCI and 222 post-PCI) with paired OFR and FFR from 9 international centres. Vessel-level diagnostic concordance of the OFR and FFR was 91% (95% confidence interval [CI]: 88%-94%), 87% (95% CI: 82%-91%), and 90% (95% CI: 87%-92%) in pre-PCI, post-PCI, and overall, respectively. The overall sensitivity, specificity, and positive and negative predictive values were 84% (95% CI: 79%-88%), 94% (95% CI: 92%-96%), 90% (95% CI: 86%-93%), and 89% (95% CI: 86%-92%), respectively. Multivariate logistic regression indicated that a low pullback speed (odds ratio [OR] 7.02, 95% CI: 1.68-29.43; p=0.008) was associated with a higher risk of obtaining OFR values at least 0.10 higher than FFR. Increasing the minimal lumen area was associated with a lower risk of obtaining an OFR at least 0.10 lower than FFR (OR 0.39, 95% CI: 0.18-0.82; p=0.013).

CONCLUSIONS

This individual patient data meta-analysis demonstrated a high diagnostic accuracy of OFR. OFR has the potential to provide an improved integration of intracoronary imaging and physiological assessment for the accurate evaluation of coronary artery disease.

Quantitative flow ratio modulated by intracoronary optical coherence tomography for predicting physiological efficacy of percutaneous coronary intervention

BACKGROUND

The combination of coronary imaging assessment and blood flow perturbation estimation has the potential to improve percutaneous coronary intervention (PCI) guidance.

OBJECTIVES

We aimed to evaluate a novel method for fast computation of Murray law-based quantitative flow ratio (μQFR) from coregistered optical coherence tomography (OCT) and angiography (OCT-modulated μQFR, OCT-μQFR) in predicting physiological efficacy of PCI.

METHODS

Patients treated by OCT-guided PCI in the OCT-arm of the Fractional Flow Reserve versus Optical Coherence Tomography to Guide RevasculariZAtion of Intermediate Coronary Stenoses trial (FORZA, NCT01824030) were included. Based on angiography and OCT before PCI, simulated residual OCT-μQFR was computed by assuming full stent expansion to the intended-to-treat segment. Plaque composition was automatically characterized using a validated artificial intelligence algorithm. Actual post-PCI OCT-μQFR pullback was computed based on coregistration of angiography and OCT acquired immediately after PCI. Suboptimal functional stenting result was defined as OCT-μQFR ≤ 0.90.

RESULTS

Paired simulated residual OCT-μQFR and actual post-PCI OCT-μQFR were obtained in 76 vessels from 74 patients. Simulated residual OCT-μQFR showed good correlation (r = 0.80, p < 0.001), agreement (mean difference = -0.02 ± 0.02, p < 0.001), and diagnostic concordance (79%, 95% confidence interval: 70%-88%) with actual post-PCI OCT-μQFR. Actual post-PCI in-stent OCT-μQFR had a median value of 0.02 and was associated with left anterior descending artery lesion location (β = 0.38, p < 0.001), higher baseline total plaque burden (β = 0.25, p = 0.031), and fibrous plaque volume (β = 0.24, p = 0.026).

CONCLUSIONS

This study based on patients enrolled in a prospective OCT-guidance PCI trial shows that simulated residual OCT-μQFR had good correlation, agreement, and diagnostic concordance with actual post-PCI OCT-μQFR. In OCT-guided procedures, OCT-μQFR in-stent pressure drop was low and was significantly predicted by pre-PCI vessel/plaque characteristics.

Predictive value of post-percutaneous coronary intervention fractional flow reserve: a systematic review and meta-analysis

AIMS

We aimed to investigate the relationship between post-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) and clinical outcome using a systematic review with a study-level meta-analysis.

METHODS AND RESULTS

MEDLINE, Embase, and CENTRAL were systematically searched for articles with clinical follow-up reporting mean or median final post-PCI FFR. The main outcome was a composite of major adverse cardiac events (MACE) including all-cause death, myocardial infarction (MI), and target vessel revascularization (TVR). Meta-regression analyses were performed on mean post-PCI FFR values. A total of 62 studies with 12 340 patients and 12 923 stented vessels were included, with follow-ups ranging from 1 to 89 months. Post-PCI FFR was not continuously associated with the rate of 1-year MACE or 1-year TVR using meta-regression models accounting for heterogeneous follow-up lengths. For studies comparing high vs. low post-PCI FFR, low post-PCI FFR was associated with high risk ratio for MACE {1.97 [95% confidence interval (CI):1.45-2.67]}, all-cause death [1.59 (95% CI: 1.08-2.34)], MI [3.18 (95% CI: 1.84-5.50)], TVR [2.08 (95% CI: 1.63-2.65)] and angina status [2.50 (95% CI: 1.53-4.06)] using different optimal cut-off values spanning from 0.80 to 0.95.

CONCLUSION

We found no clear continuous association between post-PCI FFR and clinical outcomes in this systematic study-level meta-analysis. In a subset of studies investigating binary classification, high post-PCI FFR was associated with a better clinical outcome than low post-PCI FFR.We investigated the relationship between post-percutaneous coronary intervention (PCI) fractional flow reserve (FFR) and rate of major adverse cardiac events (MACE), including all-cause death, myocardial infarction (MI), and target vessel revascularization (TVR), using a systematic review and study-level meta-analysis, pooling 12 340 patients from 62 studies. Mean post-PCI FFR was not continuously associated with a 1-year MACE rate accounting for heterogenous follow-up lengths. Still, the risk ratio favoured high post-PCI FFR for reduced MACE, all-cause death, MI, TVR, and better angina status using different cut-offs.

In-Hospital Heart Failure in Patients With Takotsubo Cardiomyopathy Due to Coronary Artery Disease: An Artificial Intelligence and Optical Coherence Tomography Study

BACKGROUND

Takotsubo syndrome (TTS) is often associated with symptoms of heart failure (HF) during the acute phase of the disease. 3-dimensional optical coherence tomography (OCT) may be used to assess the extent of angiographically silent underlying coronary artery disease (CAD). This study aims to use an artificial intelligence algorithm to analyze OCT findings and to determine whether the presence of pre-existing CAD predisposes TTS patients to present HF at admission.

METHODS

This is an observational and retrospective study that enrolled TTS patients who underwent coronary angiography and OCT examination of left anterior descending (LAD) coronary artery. Plaque characterization was automatically analyzed via an artificial intelligence model from OCT images. An angiography-derived index of microcirculatory resistance (IMRangio) using the optic flow ratio (OFR) was calculated to assess its correlation with plaque volumes.

RESULTS

Thirty-seven patients were included (94.6 % women) with a median age of 82.0 years. Ten patients (27 %) showed some degree of HF at admission. Sixty-seven coronary non-obstructive plaques were analyzed. Tissue compositional analysis showed that patients with HF had an increased overall plaque volume (79.0 mm³ vs 28.6 mm³; p = 0.011) and longer plaque lesion length (12.8 mm vs 7.2 mm; p = 0.006). Patients with HF also showed an increased percentage of lipidic and calcified plaque tissue (26.4 % vs 13.4 %; p = 0.019 and 4.5 % vs 0.0 %; p = 0.001, respectively). A moderate positive correlation was found between global overall plaque volume and IMRangio.

CONCLUSION

Increased overall plaque volume was associated with the development of HF during the acute phase of TTS, suggesting that the presence of angiographically silent underlying CAD may play a prognostic role in these patients.

Coronary physiology in the catheterisation laboratory: an A to Z practical guide

Coronary revascularisation, either percutaneous or surgical, aims to improve coronary flow and relieve myocardial ischaemia. The decision-making process in patients with coronary artery disease (CAD) remains largely based on invasive coronary angiography (ICA), even though until recently ICA could not assess the functional significance of coronary artery stenoses. Invasive wire-based approaches for physiological evaluations were developed to properly assess the ischaemic relevance of epicardial CAD. Fractional flow reserve (FFR) and later, instantaneous wave-free ratio (iFR), were shown to improve clinical outcomes in several patient subsets when used for coronary revascularisation guidance or deferral and for procedural optimisation of percutaneous coronary intervention (PCI) results. Despite accumulating evidence and positive guideline recommendations, the adoption of invasive physiology has remained quite low, mainly due to technical and economic issues as well as to operator-resistance to change. Coronary image-based computational physiology has been recently developed, with promising results in terms of accuracy and a reduction in computational time, costs, radiation exposure and risks for the patient. Lastly, the integration of intracoronary imaging and physiology allows for individualised PCI treatment, aiming at complete relief of ischaemia through optimised morpho-functional immediate procedural results. Instead of a conventional state-of-the-art review, this A to Z dictionary attempts to provide a practical guide for the application of coronary physiology in the catheterisation laboratory, exploring several methods, their pitfalls, and useful tips and tricks.

Optical coherence tomography in coronary atherosclerosis assessment and intervention

Since optical coherence tomography (OCT) was first performed in humans two decades ago, this imaging modality has been widely adopted in research on coronary atherosclerosis and adopted clinically for the optimization of percutaneous coronary intervention. In the past 10 years, substantial advances have been made in the understanding of in vivo vascular biology using OCT. Identification by OCT of culprit plaque pathology could potentially lead to a major shift in the management of patients with acute coronary syndromes. Detection by OCT of healed coronary plaque has been important in our understanding of the mechanisms involved in plaque destabilization and healing with the rapid progression of atherosclerosis. Accurate detection by OCT of sequelae from percutaneous coronary interventions that might be missed by angiography could improve clinical outcomes. In addition, OCT has become an essential diagnostic modality for myocardial infarction with non-obstructive coronary arteries. Insight into neoatherosclerosis from OCT could improve our understanding of the mechanisms of very late stent thrombosis. The appropriate use of OCT depends on accurate interpretation and understanding of the clinical significance of OCT findings. In this Review, we summarize the state of the art in cardiac OCT and facilitate the uniform use of this modality in coronary atherosclerosis. Contributions have been made by clinicians and investigators worldwide with extensive experience in OCT, with the aim that this document will serve as a standard reference for future research and clinical application.

Feasibility of Quantitative Flow Ratio Virtual Stenting for Guidance of Serial Coronary Lesions Intervention

Background

Coronary physiology measurement in serial coronary lesions with multiple stenoses is challenging. Therefore, we evaluated the feasibility of Murray fractal law‐based quantitative flow ratio (μQFR) virtual stenting for guidance of serial coronary lesions intervention.

Methods and Results

Patients who underwent elective coronary angiography and had 2 serial de novo coronary lesions of 30% to 90% diameter stenosis by visual estimation were prospectively enrolled. μQFR and fractional flow reserve (FFR) were assessed after coronary angiography. In vessels with an FFR ≤0.80, the lesion with the larger pressure gradient was considered to be the primary lesion and treated firstly, followed by FFR measurement. The second lesion was stented when FFR ≤0.80. All μQFR and predicted μQFR after stenting were calculated from diagnostic coronary angiography before interventions, with the analysts masked to the FFR data. A total of 54 patients with 61 target vessels were interrogated. Percutaneous coronary intervention was performed in 44 vessels with FFR ≤0.80. After stenting the primary lesions, 14 nonprimary lesions had FFR ≤0.80 and a second drug‐eluting stent was implanted. There was excellent correlation (r=0.97, P<0.001) and good agreement (mean difference: 0.00±0.03) between baseline μQFR and FFR in identifying flow‐limiting lesions. Per‐vessel diagnostic accuracy of μQFR on de novo lesions was 96.7% (95% CI, 88.7%–99.6%). μQFR and FFR are highly consistent (93.2%) in identifying the primary lesion requiring revascularization. After stenting the primary lesions, per‐vessel diagnostic accuracy of predicted μQFR for identifying the significance of the nonprimary lesion was 90.9%. Predicted residual μQFR with virtual stenting was higher than final FFR (mean difference: 0.05±0.06).

Conclusions

In vessels with serial coronary lesions, virtual stenting by μQFR can identify the primary flow‐limiting lesion for revascularization.

Radial wall strain: a novel angiographic measure of plaque composition and vulnerability

BACKGROUND

The lipid-to-cap ratio (LCR) and thin-cap fibroatheroma (TCFA) derived from optical coherence tomography (OCT) are indicative of plaque vulnerability.

AIMS

We aimed to explore the association of a novel method to estimate radial wall strain (RWS) from angiography with plaque composition and features of vulnerability assessed by OCT.

METHODS

Anonymised data from patients with intermediate stenosis who underwent coronary angiography (CAG) and OCT were analysed in a core laboratory. Angiography-derived RWSmax was computed as the maximum deformation of lumen diameter throughout the cardiac cycle, expressed as a percentage of the largest lumen diameter. The LCR and TCFA were automatically determined on OCT images by a recently validated algorithm based on artificial intelligence.

RESULTS

OCT and CAG images from 114 patients (124 vessels) were analysed. The average time for the analysis of RWSmax was 57 (39-82) seconds. The RWSmax in the interrogated plaques was 12% (10-15%) and correlated positively with the LCR (r=0.584; p<0.001) and lipidic plaque burden (r=0.411; p<0.001), and negatively with fibrous cap thickness (r= -0.439; p<0.001). An RWSmax >12% was an angiographic predictor for an LCR >0.33 (area under the curve [AUC]=0.86, 95% confidence interval [CI]: 0.78-0.91; p<0.001) and TCFA (AUC=0.72, 95% CI: 0.63-0.80; p<0.001). Lesions with RWSmax >12% had a higher prevalence of TCFA (22.0% versus 1.5%; p<0.001), thinner fibrous cap thickness (71 μm versus 101 μm; p<0.001), larger lipidic plaque burden (23.3% versus 15.4%; p<0.001), and higher maximum LCR (0.41 versus 0.18; p<0.001) compared to lesions with RWSmax ≤12%.

CONCLUSIONS

Angiography-derived RWS was significantly correlated with plaque composition and known OCT features of plaque vulnerability in patients with intermediate coronary stenosis.

Coronary functional assessment in non-obstructive coronary artery disease: Present situation and future direction

Non-obstructive coronary artery disease (CAD), which is defined as coronary stenosis <50%, has been increasingly recognized as an emerging entity in clinical practice. Vasomotion abnormality and coronary microvascular dysfunction are two major mechanisms contributing to the occur of angina with non-obstructive CAD. Although routine coronary functional assessment is limited due to several disadvantages, functional evaluation can help to understand the pathophysiological mechanism and/or to exclude specific etiologies. In this review, we summarized the potential mechanisms involved in ischemia with non-obstructive coronary arteries (INOCA) and myocardial infarction with non-obstructive coronary arteries (MINOCA), the two major form of non-obstructive CAD. Additionally, we reviewed currently available functional assessment indices and their use in non-obstructive CAD. Furthermore, we speculated that novel technique combined anatomic and physiologic parameters might provide more individualized therapeutic choice for patients with non-obstructive CAD.

In vivo detection of plaque erosion by intravascular optical coherence tomography using artificial intelligence

Plaque erosion is one of the most common underlying mechanisms for acute coronary syndrome (ACS). Optical coherence tomography (OCT) allows in vivo diagnosis of plaque erosion. However, challenge remains due to high inter- and intra-observer variability. We developed an artificial intelligence method based on deep learning for fully automated detection of plaque erosion in vivo, which achieved a recall of 0.800 ± 0.175, a precision of 0.734 ± 0.254, and an area under the precision-recall curve (AUC) of 0.707. Our proposed method is in good agreement with physicians, and can help improve the clinical diagnosis of plaque erosion and develop individualized treatment strategies for optimal management of ACS patients.

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.

Optimising PCI by Intracoronary Image-guidance

Evidence to support the use of intracoronary imaging (ICI) in guiding percutaneous coronary intervention (PCI) is growing, with observational and randomized controlled trials demonstrating a benefit in acute procedural and clinical outcomes. ICI provides an opportunity to guide PCI, detailing the nature of the coronary disease, potentially influencing lesion preparation and stent selection. Following stent deployment, ICI offers a detailed assessment of lesion coverage, associated vessel trauma and stent expansion. Consensus statements have emphasized the role of ICI and detailed the parameters of stent optimization. However, intracoronary imaging is not adopted widely yet. Significant global differences in the uptake of ICI have been reported, with the vast majority of PCI being angiographically-guided. The three major barriers to the implementation of ICI include, in order of impact, prohibitive cost, prolongation of procedure time and local regulatory issues for use. However, it is our belief that a lack of education and the associated challenges of ICI interpretation provide the greatest barrier to adoption. We hope that this review of the role of ICI in PCI optimization will provide a platform for PCI operators to gain confidence in the utilization of ICI to enhance outcomes for their patients.

Coronary physiologic assessment based on angiography and intracoronary imaging

Despite the current evidence supporting clinical benefits of fractional flow reserve (FFR), its uptake in the cardiac catheterization laboratory has been slow due to procedural cost and increased time with the need for maximum hyperemia. Recently, novel physiological indices derived from coronary angiography and intracoronary imaging have emerged to overcome issues with a wire-based FFR. Angiography-based FFR can be measured without vessel instrumentation and has shown excellent diagnostic performance using wire-based FFR as the reference standard. Thus, angiography-based FFR may facilitate coronary functional assessment before and after percutaneous coronary intervention (PCI). Angiography-based index of microcirculatory resistance (IMR) is another new computational index for assessing the coronary microcirculation. Although angiography-derived IMR remains in an early phase of development and requires further validation, its less-invasive nature may help broaden the adoption of microvascular functional assessment in various conditions such as myocardial infarction and cardiac allograft vasculopathy. Lastly, computational FFR based on intravascular ultrasound and optical coherence tomography allows detailed lesion assessment from both morphological and functional standpoints. Given a growing interest in physiology-guided PCI optimization strategies, intravascular imaging-based FFR may become the main assessment tool to confirm successful PCI.