Association between optical coherence tomography-defined culprit morphologies and changes in hyperemic coronary flow after elective stenting assessed by transthoracic Doppler echocardiography.

BACKGROUND: Stress-transthoracic Doppler echocardiography (S-TDE) provides a noninvasive assessment of coronary flow parameters in the left anterior descending artery (LAD). However, the association between morphological characteristics and coronary flow changes after elective percutaneous coronary intervention (PCI) remains unclear. We aimed to evaluate the relationships between periprocedural coronary flow changes observed on S-TDE and lesion-specific plaque characteristics obtained by optical coherence tomography (OCT) in the interrogated vessels in patients with chronic coronary syndrome (CCS). METHODS AND RESULTS: Patients with CCS who underwent pre- and post-PCI S-TDE and elective fractional flow reserve (FFR)-guided PCI under OCT guidance for de novo single LAD lesions were included. S-TDE-derived hyperemic diastolic peak flow velocity (hDPV) was used as a surrogate for coronary flow. Lesions were categorized into two groups based on the %hDPV increase or decrease. The baseline clinical, physiological, and OCT findings were compared between the groups. In total, 103 LAD lesions were studied in 103 patients. After PCI, hDPV significantly increased from 55.6 cm/s to 69.5 cm/s (P<0.01), with a median %hDPV increase of 27.2 (6.32-59.1) %, while %hDPV decreased in 20 (19.4%) patients. The FFR improved in all patients. On OCT, layered plaques were more frequently present in the culprit vessels in the %hDPV-decrease group than in the %hDPV-increase group (85.0% vs. 50.6%, P = 0.01). Multivariable logistic regression analysis showed that the presence of layered plaques and high pre-PCI hDPV were independent predictors of %hDPV decrease. CONCLUSIONS: In patients who underwent successful uncomplicated elective PCI for de novo single LAD lesions, the presence of layered plaques was independently associated with hyperemic coronary flow decrease as assessed by S-TDE.

Changes in absolute coronary flow and microvascular resistance during exercise in patients with ANOCA.

BACKGROUND: Whether saline-induced hyperaemia captures exercise-induced coronary flow regulation remains unknown. AIMS: Through this study, we aimed to describe absolute coronary flow (Q) and microvascular resistance (Rµ) adaptation during exercise in participants with angina with non-obstructive coronary artery disease (ANOCA) and to explore the correlations between saline- and exercise-derived coronary flow reserve (CFR) and microvascular resistance reserve (MRR). METHODS: Rµ, Q, CFR and MRR were assessed in the left anterior descending artery using continuous thermodilution with saline infusion at 10 mL/min (rest), 20 mL/min (hyperaemia) and finally at a 10 mL/min infusion rate during stress testing with a dedicated supine cycling ergometer. An incremental workload of 30 watts every two minutes was applied. A saline-derived CFR (CFRsaline) cutoff <2.5 was used to identify coronary microvascular dysfunction (CMD). RESULTS: CFRsaline-defined CMD was observed in 53.3% of the participants (16/30). While cycling, these patients less of an ability to increase Q (7 [interquartile range [IQR] 30.5-103.0] vs 21 [IQR 5.8-45.0] mL/min/30 watts; p=0.01) due to a smaller decrease of Rµ (109 {IQR 32-286} vs 202 [IQR 102-379] Wood units [WU]/30 watts; p<0.01) as compared with the group with normal CFRsaline. In the overall population, CFRsaline and exercise-derived CFR (CFRexercise) were 2.70±0.90 and 2.85±1.54, respectively, with an agreement classification of 83.3%. A good correlation between saline and exercise techniques for both CFR (r=0.73; p<0.0001) and MRR (r=0.76; p<0.0001) was observed. Among participants with normal CFRsaline, 28.7% (4/14) had an impaired CFRexercise <2.5 at the peak of exercise due to a moderate and late decrease of Rµ. CONCLUSIONS: Saline-induced hyperaemia provided a valid surrogate for exercise physiology independently of the absolute level of CFR and MRR, although exercise provided more granularity to evaluate adaptation among participants with exercise-related CMD.

Correlation and consistency between resting full-cycle ratio and fractional flow reserve in assessing coronary artery function in a Chinese real-world cohort with non-ST-segment elevation acute coronary syndrome: a retrospective observational study.

OBJECTIVE: The study aimed to investigate the correlation and consistency between resting full-cycle ratio (RFR) and fractional flow reserve (FFR) in functional assessment of coronary arteries in a Chinese real-world cohort with non-ST-segment elevation acute coronary syndrome (NSTE-ACS). DESIGN: Retrospective study. SETTING: A single-centre study in China. PARTICIPANTS: A total of 292 diseased vessels of 226 Chinese patients with NSTE-ACS at Cangzhou Central Hospital of Hebei Medical University from September 2021 to June 2023 were included. METHODS: The correlation between RFR and FFR, resting ratio of distal coronary artery pressure (Pd) to aortic pressure (Pa) and FFR were analysed by using Person correlation, and the consistency between RFR and FFR, resting Pd/Pa and FFR were assessed by Bland-Altman test. The diagnostic values of RFR and resting Pd/Pa for predicting FFR≤0.80 were evaluated according to the receiver operating characteristic (ROC) curves. RESULTS: RFR and resting Pd/Pa were significantly correlated with FFR, and correlation coefficients were 0.787 (p<0.001) and 0.765 (p<0.001), respectively. We found no significant differences between RFR and FFR or between resting Pd/Pa and FFR. The areas under the ROC curves for predicting FFR≤0.80 were 0.883 (p<0.001) for RFR and 0.858 (p<0.001) for resting Pd/Pa, and the optimal critical values were 0.91 for RFR and 0.93 for resting Pd/Pa. The accuracy, sensitivity, specificity and positive and negative predictive values of RFR≤0.91 for predicting FFR≤0.80 were 79.1%, 84.0%, 76.6%, 65.1% and 90.2%, respectively. CONCLUSION: The current study suggests that RFR exhibits a good correlation and consistency with FFR in patients with NSTE-ACS. RFR is expected to significantly enhance the application of coronary artery functional assessment in clinical practice, thereby providing patients with more precise revascularisation strategies.

CT Myocardial Perfusion and CT-FFR versus Invasive FFR for Hemodynamic Relevance of Coronary Artery Disease.

Background CT-derived fractional flow reserve (CT-FFR) and dynamic CT myocardial perfusion imaging enhance the specificity of coronary CT angiography (CCTA) for ruling out coronary artery disease (CAD). However, evidence on comparative diagnostic value remains scarce. Purpose To compare the diagnostic accuracy of CCTA plus CT-FFR, CCTA plus CT perfusion, and sequential CCTA plus CT-FFR and CT perfusion for detecting hemodynamically relevant CAD with that of invasive angiography. Materials and Methods This secondary analysis of a prospective study included patients with chest pain referred for invasive coronary angiography at nine centers from July 2016 to September 2019. CCTA and CT perfusion were performed with third-generation dual-source CT scanners. CT-FFR was assessed on-site. Independent core laboratories analyzed CCTA alone, CCTA plus CT perfusion, CCTA plus CT-FFR, and a sequential approach involving CCTA plus CT-FFR and CT perfusion for the presence of hemodynamically relevant stenosis. Invasive coronary angiography with invasive fractional flow reserve was the reference standard. Diagnostic accuracy metrics and the area under the receiver operating characteristic curve (AUC) were compared with the Sign test and DeLong test. Results Of the 105 participants (mean age, 64 years ± 8 [SD]; 68 male), 49 (47%) had hemodynamically relevant stenoses at invasive coronary angiography. CCTA plus CT-FFR and CCTA plus CT perfusion showed no evidence of a difference for participant-based sensitivities (90% vs 90%, P > .99), specificities (77% vs 79%, P > .99) and vessel-based AUCs (0.84 [95% CI: 0.77, 0.91] vs 0.83 [95% CI: 0.75, 0.91], P = .90). Both had higher participant-based specificity than CCTA alone (54%, both P < .001) without evidence of a difference in sensitivity between CCTA (94%) and CCTA plus CT perfusion (P = .50) or CCTA plus CT-FFR (P = .63). The sequential approach combining CCTA plus CT-FFR with CT perfusion achieved higher participant-based specificity than CCTA plus CT-FFR (88% vs 77%, P = .03) without evidence of a difference in participant-based sensitivity (88% vs 90%, P > .99) and vessel-based AUC (0.85 [95% CI: 0.77, 0.93], P = .78). Compared with CCTA plus CT perfusion, the sequential approach showed no evidence of a difference in participant-based sensitivity (P > .99), specificity (P = .06), or vessel-based AUC (P = .54). Conclusion There was no evidence of a difference in diagnostic accuracy between CCTA plus CT-FFR and CCTA plus CT perfusion for detecting hemodynamically relevant CAD. A sequential approach combining CCTA plus CT-FFR with CT perfusion led to improved participant-based specificity with no evidence of a difference in sensitivity compared with CCTA plus CT-FFR. ClinicalTrials.gov registration no.: NCT02810795 © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Sinitsyn in this issue.

Intracoronary Imaging for Changing Therapeutic Decisions in Patients with Multivascular Coronary Artery Disease.

Background and Objectives: Atherosclerotic disease is a major contributor to heart failure, stroke, and myocardial infarction, significantly lowering the quality of life and life expectancy and placing a significant burden on healthcare. Not all lesions deemed non-significant are benign, and conversely, not all significant lesions are causative of ischemia. Fractional flow reserve (FFR) provides a functional assessment of coronary lesions, while optical coherence tomography (OCT) offers detailed imaging of plaque morphology, aiding in therapeutic decision-making. The objective of this study was to evaluate the utility of OCT and FFR as adjunctive tools in the catheterization laboratory for guiding therapeutic decisions in patients with multivessel disease for non-culprit vessels. Specifically, we aimed to assess how OCT and FFR influence therapeutic decision-making in patients with multivessel coronary artery disease. Materials and Methods: A total of 36 patients with acute coronary syndrome (ACS) and multivessel disease were randomized 1:1 into two groups: one guided by FFR alone and the other by a combination of FFR and OCT. For the FFR group, revascularization decisions for non-culprit lesions were based solely on FFR measurements. If the FFR was >0.8, the procedure was concluded, and the patient received maximal medical treatment. If the FFR was ≤0.8, a stent was placed. For the FFR + OCT group, if the FFR was >0.8, the revascularization decision was based on OCT findings. If there were no vulnerable plaques (VP), the procedure was concluded, and the patient received maximal medical treatment. If OCT imaging indicated VP, then the patient underwent revascularization. If the FFR was ≤0.8, the patient underwent revascularization regardless of OCT findings. Results: OCT imaging altered the therapeutic decision in 11 cases where FFR measurements were above 0.8, but the lesions were characterized as VP. Analyzing the total change in the decision to stent, 4 cases in the FFR group and 15 cases in the FFR and OCT groups (4 based on FFR and 11 on OCT) revealed a statistically significant difference (p = 0.0006; Relative Risk = 0.2556; 95% CI: 0.1013 to 0.5603). When analyzing the change in the total decision both to stent and not to stent, we observed a statistically significant difference, with Group 1 having 7 cases and Group 2 having 15 cases (p = 0.0153; Relative Risk = 0.4050; 95% CI: 0.2004 to 0.7698. Conclusions: Based on the findings of this study, OCT significantly increases the percentage of stenting procedures by identifying vulnerable lesions. The use of intracoronary imaging facilitates the timely identification and treatment of these vulnerable lesions. This underscores the crucial role of OCT in enhancing the precision of coronary interventions by ensuring timely intervention for vulnerable lesions, thereby potentially improving patient outcomes.

Outcomes According to Coronary Disease Complexity and Optimal Thresholds to Guide Revascularization Approach: FAME 3 Trial.

BACKGROUND: Coronary disease complexity is commonly used to guide revascularization strategy in patients with multivessel disease (MVD). OBJECTIVES: The aim of this study was to assess the interactive effects of coronary complexity on percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) outcomes and identify the optimal threshold at which PCI can be considered a reasonable option. METHODS: A total of 1,444 of 1,500 patients with MVD from the FAME (Fractional Flow Reserve versus Angiography for Multi-vessel Evaluation) 3 randomized trial were included in the analysis (710 CABG vs 734 PCI). SYNTAX (Synergy Between PCI With Taxus and Cardiac Surgery) scores were transformed into restricted cubic splines, and logistic regression models were fitted, with multiplicative interaction terms for revascularization strategy. Optimal thresholds at which PCI is a reasonable alternative to CABG were determined on the basis of Cox regression model performance. RESULTS: The mean SYNTAX score (SS) was 25.9 ± 7.1. SS was associated with 1-year major adverse cardiac and cerebrovascular events among PCI patients and 3-year death, myocardial infarction, and stroke among CABG patients. Significant interactions were present between revascularization strategy and SS for 1- and 3-year composite endpoints (P for interaction <0.05 for all). In Cox regression models, outcomes were comparable between CABG and PCI for the 3-year primary endpoint for SS ≤24 (P = 0.332), with 44% of patients below this threshold and 32% below the conventional SS threshold of ≤22. CONCLUSIONS: In patients with MVD without left main disease, PCI and CABG outcomes remain comparable up to SS values in the mid- rather than low 20s, which allows the identification of a greater proportion of patients in whom PCI may be a reasonable alternative to CABG.

Influence of the pressure wire on the fractional flow reserve calculation: CFD analysis of an ideal vessel and clinical patients with stenosis.

BACKGROUND AND OBJECTIVE: Fractional Flow Reserve (FFR) is generally considered the gold standard in hemodynamics to assess the impact of a stenosis on the blood flow. The standard procedure to measure involves the displacement of a pressure guide along the circulatory system until it is placed next to the lesion to be analyzed. The main objective of the present study is to analyze the influence of the pressure guide on the invasive FFR measurements and its implications in clinical practice. METHODS: We studied the influence of pressure wires on the measurement of Fractional Flow Reserve (FFR) through a combination of Computational Fluid Dynamics (CFD) simulations using 45 clinical patient data with 58 lesions and ideal geometries. The analysis is conducted considering patients that were subjected to a computer tomography and also have direct measurements using a pressure guide. Influence of the stenosis severity, degree of occlusion and blood viscosity has also been studied. RESULTS: The influence of pressure wires specifically affects severe stenosis with a lumen diameter reduction of 50 % or greater. This type of stenosis leads to reduced hyperemic flow and increased coronary pressure drop. Thus, we identified that the placement of wires during FFR measurements results in partial obstruction of the coronary artery lumen, leading to increased pressure drop and subsequent reduction in blood flow. The severity of low FFR values associated with severe stenosis may be prone to overestimation when compared to stenosis without severe narrowing. These results have practical implications, particularly in the interpretation of lesions falling within the "gray zone" (0,75-0,80). CONCLUSIONS: The pressure wire's presence significantly alters the flow on severe lesions, which has an impact on the FFR calculation. In contrast, the impact of the pressure wire appears to be reduced when the FFR is larger than 0.8. The findings provide critical information for physicians, emphasizing the need for cautious interpretation of FFR values, particularly in severe stenosis. It also offers insights into improving the correlation between FFRct models and invasive measurements by incorporating the influence of pressure wires.

Noninvasive and fast method of calculation for instantaneous wave-free ratio based on haemodynamics and deep learning.

BACKGROUND AND OBJECTIVES: Instantaneous wave-free ratio (iFR) is a new invasive indicator of myocardial ischaemia, and its diagnostic performance is as good as the "gold standard" of myocardial ischaemia diagnosis: fractional flow reserve (FFR). iFR can be approximated by iFRCT, which is calculated based on noninvasive coronary CT angiography (CTA) images and computational fluid dynamics (CFD). However, the existing methods for calculating iFRCT fail to accurately simulate the resting state of the coronary artery, resulting in low computational accuracy. Furthermore, the use of CFD technology limits its computational efficiency, making it difficult to meet clinical application needs. The role of coronary microcirculatory resistance compensation suggests that microcirculatory resistance can be adaptively reduced to compensate for increases in coronary stenotic resistance, thereby maintaining stable myocardial perfusion in the resting state. It is therefore necessary to consider this compensation mechanism to establish a high-fidelity microcirculation resistance model in the resting state in line with human physiology, and so to achieve accurate calculation of iFRCT. METHODS: In this study we successfully collected clinical data, such as FFR, in 205 stenotic vessels from 186 patients with coronary heart disease. A neural network model was established to predict coronary artery stenosis resistance. Based on the compensation mechanism of coronary microcirculation resistance, an iterative solution algorithm for microcirculation resistance in the resting state was developed. Combining the two methods, a simplified single-branch model combining coronary stenosis and microcirculation resistance was established, and the noninvasive and rapid numerical calculation of iFRCT was performed. RESULTS: The results showed that the mean squared error (MSE) between the pressure drop predicted by the neural network value for the coronary artery stenosis model and the ground truth in the test set was 0.053 %, and correlation analysis proved that there was a good correlation between them (r = 0.99, p < 0.001). With reference to clinical diagnosis of myocardial ischaemia (using FFR as the gold standard), the diagnostic accuracy of the iFRCT calculation model for the 205 cases was 88.29 % (r = 0.71, p < 0.001), and the total calculation time was < 8 s. CONCLUSIONS: The results of this study demonstrate the utility of a simplified single-branch model in an iFRCT calculation method based on haemodynamics and deep learning, which is important for noninvasive and rapid diagnosis of myocardial ischaemia.

Prognostic impact of quantitative flow ratio (QFR)-consistent complete revascularization in patients with myocardial infarction and multivessel coronary artery disease.

BACKGROUND: Complete revascularization is associated with improved outcomes in patients with myocardial infarction and multivessel coronary artery disease. Quantitative flow ratio (QFR) represents an emerging angiography-based tool for functional lesion assessment. The present study investigated the prognostic impact of QFR-consistent complete revascularization in patients with myocardial infarction and multivessel disease. METHODS: A total of 792 patients with myocardial infarction and multivessel disease were enrolled in the analysis. Post-hoc QFR analyses of 1,320 nonculprit vessels were performed by investigators blinded to clinical outcomes. The primary endpoint was a composite of all-cause death, nonculprit vessel related nonfatal myocardial infarction, and ischemia-driven revascularization at 2 years after index myocardial infarction. Patients were stratified into a QFR-consistent PCI group (n = 646) and a QFR-inconsistent PCI group (n = 146), based on whether the intervention was congruent with the QFR-determined functional significance of the nonculprit lesions. RESULTS: The primary endpoint occurred in a total of 22 patients (3.4%) in the QFR-consistent PCI group and in 27 patients (18.5%) in the QFR-inconsistent group (HR 0.17, 95% CI 0.10-0.30, P < .001).The difference in the primary endpoint was driven by reduced rates of nonfatal myocardial infarction (2.0% vs. 15.1%; HR 0.13, 95% CI 0.06-0.25; P < .001) and ischemia-driven revascularization (1.2% vs. 5.5%; HR 0.21, 95% CI 0.08-0.57; P = .001) in the QFR-consistent PCI group. CONCLUSIONS: Among patients with myocardial infarction and multivessel disease, a QFR-consistent complete revascularization was associated with a reduced risk of all-cause mortality, nonfatal myocardial infarction, and ischemia-driven revascularization. These findings underline the value of angiography-based functional lesion assessment for personalized revascularization strategies.

Accuracy of subtraction fractional flow reserve with computed tomography in identifying early revascularization in patients with coronary artery disease.

OBJECTIVES: The diagnostic performance of fractional flow reserve with computed tomography (FFR-CT) is affected by the presence of calcified plaque. Subtraction can remove the influence of calcification in coronary computed tomography angiography (CCTA) to increase confidence in the diagnosis of coronary artery stenosis. Our purpose is to investigate the accuracy of post-subtraction FFR-CT in predicting early revascularization. DESIGN: Based on CCTA data of 237 vessels from 79 patients with coronary artery disease, subtraction CCTA images were obtained at a local post-processing workstation, and the conventional and post-subtraction FFR-CT measurements and the difference in proximal and distal FFR-CT values of the narrowest segment of the vessel (ΔFFR-CT) were analyzed for their accuracy in predicting early coronary artery hemodynamic reconstruction. RESULTS: With FFR-CT ≤ 0.8 as the criterion, the accuracy of conventional and post-subtraction FFR-CT measurements in predicting early revascularization was 73.4% and 77.2% at the patient level, and 64.6% and 72.2% at the vessel level, respectively. The specificity of post-subtraction FFR-CT measurements was significantly higher than that of conventional FFR-CT at both the patient and vessel levels (P of 0.013 and 0.015, respectively). At the vessel level, the area under the curve of receiver operating characteristic was 0.712 and 0.797 for conventional and post-subtraction ΔFFR-CT, respectively, showing a difference (P = 0.047), with optimal cutoff values of 0.07 and 0.11, respectively. CONCLUSION: The post-subtraction FFR-CT measurements enhance the specificity in predicting early revascularization. The post-subtraction ΔFFR-CT value of the stenosis segment > 0.11 may be an important indicator for early revascularization.

Higher processing repeatability of myocardial flow reserve calculated using net retention model compared to one compartment model in SPECT studies.

Dynamic assessment of myocardial blood flow (MBF) and myocardial flow reserve (MFR) provides additional information that can improve diagnostic accuracy of radionuclide myocardial perfusion imaging in some clinical situations. This study assessed processing repeatability of these parameters calculated using two models-net retention (RET) and one compartment (1CM) in dynamic SPECT studies, using the latest version of Corridor 4DM software (v2024). Data of 107 patients were analyzed retrospectively (57 of whom were assessed in our previous study using 4DM v2015). Dynamic SPECT studies were carried out using a routine two-day rest-dipyridamole protocol. Data was processed in 4DM v2024 twice by one operator and once by another operator. Automatic heart image positioning during post-processing in 4DM v2024 was significantly improved compared to v2015, reducing the number of studies requiring extensive manual corrections from 41 to 12%. This significantly improved interobserver processing repeatability of MFR values in RCA territory compared to our previous study using v2015-from r = 0.67 to 0.85 (p = 0.0034). Interobserver processing repeatability of MBF and MFR in all 107 patients was significantly better in RET model compared to 1CM model. In conclusion, RET model is more reliable for calculating MBF and MFR values based on dynamic SPECT studies.

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.