Photon-Counting Detector CT Virtual Monoenergetic Images for Coronary Artery Stenosis Quantification: Phantom and In Vivo Evaluation

BACKGROUND. Calcium blooming causes stenosis overestimation on coronary CTA. OBJECTIVE. The purpose of this article was to evaluate the impact of virtual monoenergetic imaging (VMI) reconstruction level on coronary artery stenosis quantification using photon-counting detector (PCD) CT. METHODS. A phantom containing two custom-made vessels (representing 25% and 50% stenosis) underwent PCD CT acquisitions without and with simulated cardiac motion. A retrospective analysis was performed of 33 patients (seven women, 26 men; mean age, 71.3 ± 9.0 [SD] years; 64 coronary artery stenoses) who underwent coronary CTA by PCD CT followed by invasive coronary angiography (ICA). Scans were reconstructed at nine VMI energy levels (40-140 keV). Percentage diameter stenosis (PDS) was measured, and bias was determined from the ground-truth stenosis percentage in the phantom and ICA-derived quantitative coronary angiography measurements in patients. Extent of blooming artifact was measured in the phantom and in calcified and mixed plaques in patients. RESULTS. In the phantom, PDS decreased for 25% stenosis from 59.9% (40 keV) to 13.4% (140 keV) and for 50% stenosis from 81.6% (40 keV) to 42.3% (140 keV). PDS showed lowest bias for 25% stenosis at 90 keV (bias, 1.4%) and for 50% stenosis at 100 keV (bias, -0.4%). Blooming artifacts decreased for 25% stenosis from 61.5% (40 keV) to 35.4% (140 keV) and for 50% stenosis from 82.7% (40 keV) to 52.1% (140 keV). In patients, PDS for calcified plaque decreased from 70.8% (40 keV) to 57.3% (140 keV), for mixed plaque decreased from 69.8% (40 keV) to 56.3% (140 keV), and for noncalcified plaque was 46.6% at 40 keV and 54.6% at 140 keV. PDS showed lowest bias for calcified plaque at 100 keV (bias, 17.2%), for mixed plaque at 140 keV (bias, 5.0%), and for noncalcified plaque at 40 keV (bias, -0.5%). Blooming artifacts decreased for calcified plaque from 78.4% (40 keV) to 48.6% (140 keV) and for mixed plaque from 73.1% (40 keV) to 44.7% (140 keV). CONCLUSION. For calcified and mixed plaque, stenosis severity measurements and blooming artifacts decreased at increasing VMI reconstruction levels. CLINICAL IMPACT. PCD CT with VMI reconstruction helps overcome current limitations in stenosis quantification on coronary CTA.

Determinants and Prognoses of Visual-Functional Mismatches After Mechanical Reperfusion in ST-Elevation Myocardial Infarction

Background

Discordance between the anatomy and physiology of the coronary has important implications for managing patients with stable coronary disease, but its significance in ST-elevation myocardial infarction has not been fully elucidated.

Methods

The retrospective study involved patients diagnosed with ST-elevation myocardial infarction (STEMI) who underwent percutaneous coronary intervention (PCI), along with quantitative coronary angiography (QCA) and quantitative flow ratio (QFR) assessments. Patients were stratified into four groups regarding the severity of the culprit vessel, both visually and functionally: concordantly negative (QCA-diameter stenosis [DS] ≤ 50% and QFR > 0.80), mismatch (QCA-DS > 50% and QFR > 0.80), reverse mismatch (QCA-DS ≤ 50% and QFR ≤ 0.80), and concordantly positive (QCA-DS > 50% and QFR ≤ 0.80). Multivariable logistic regression analyses were conducted to identify the clinical factors linked to visual-functional mismatches. Kaplan‒Meier analysis was conducted to estimate the 18-month adverse cardiovascular events (MACE)-free survival between the four groups.

Results

The study involved 310 patients, with 68 presenting visual-functional mismatch, and 51 exhibiting reverse mismatch. The mismatch was associated with higher angiography-derived microcirculatory resistance (AMR) (adjusted odds ratio [aOR]=1.016, 95% CI: 1.010-1.022, P<0.001). Reverse mismatch was associated with larger area stenosis (aOR=1.044, 95% CI: 1.004-1.086, P=0.032), lower coronary flow velocity (aOR=0.690, 95% CI: 0.567-0.970, P<0.001) and lower AMR (aOR=0.947, 95% CI: 0.924-0.970, P<0.001). Additionally, the mismatch group showed the worst 18-month MACE-free survival among the four groups (Log rank test p = 0.013).

Conclusion

AMR plays a significant role in the occurrence of visual-functional mismatches between QCA-DS and QFR, and the mismatch group showed the worst prognosis.

Coronary Artery Stenosis Evaluation by Angiography-Derived FFR: Validation by Positron Emission Tomography and Invasive Thermodilution

BACKGROUND

Fractional flow reserve (FFR) derived from invasive coronary angiography (QFR) is promising for evaluation of intermediate coronary artery stenosis.

OBJECTIVES

The authors aimed to compare the diagnostic performance of QFR and the guideline-recommended invasive FFR using 82Rubidium positron emission tomography (82Rb-PET) myocardial perfusion imaging as reference standard.

METHODS

This is a prospective, observational study of symptomatic patients with suspected obstructive coronary artery disease on coronary computed tomography angiography (≥50% diameter stenosis in ≥1 vessel). All patients were referred to 82Rb-PET and invasive coronary angiography with FFR and QFR assessment of all intermediate (30%-90% diameter stenosis) stenoses. Main analyses included a comparison of the ability of QFR and FFR to identify reduced myocardial blood flow (<2 mL/g/min) during vasodilation and/or relative perfusion abnormalities (summed stress score ≥4 in ≥2 adjacent segments).

RESULTS

A total of 250 patients (320 vessels) with indication for invasive physiological assessment were included. The continuous relationship of 82Rb-PET stress myocardial blood flow per 0.10 increase in FFR was +0.14 mL/g/min (95% CI: 0.07-0.21 mL/g/min) and +0.08 mL/g/min (95% CI: 0.02-0.14 mL/g/min) per 0.10 QFR increase. Using 82Rb-PET as reference, QFR and FFR had similar diagnostic performance on both a per-patient level (accuracy: 73%; 95% CI: 67%-79%; vs accuracy: 71%; 95% CI: 64%-78%) and per-vessel level (accuracy: 70%; 95% CI: 64%-75%; vs accuracy: 68%; 95% CI: 62%-73%). The per-vessel feasibility was 84% (95% CI: 80%-88%) for QFR and 88% (95% CI: 85%-92%) for FFR by intention-to-diagnose analysis.

CONCLUSIONS

With 82Rb-PET as reference modality, the wire-free QFR solution showed similar diagnostic accuracy as invasive FFR in evaluation of intermediate coronary stenosis. (DAN-NICAD - Danish Study of Non-Invasive Diagnostic Testing in Coronary Artery Disease; NCT02264717).

Comparison of quantitative flow ratio with instantaneous wave-free ratio and resting full-cycle ratio during daily routine in the catheterization laboratory

BACKGROUND

Quantitative flow ratio (QFR) is a novel, software-based method to evaluate the physiology of coronary lesions. The aim of this study was to compare QFR with the established invasive measurements of coronary blood flow using instantaneous wave-free ratio (iFR) or resting full-cycle ratio (RFR) in daily cathlab routine.

METHODS

102 patients with stable coronary artery disease and a coronary stenosis of 40%-90% were simultaneously assessed with QFR and iFR or RFR. QFR-computation was performed by two certified experts using the appropriate software (QAngio XA 3D 3.2).

RESULTS

QFR showed a significant correlation (r = 0.75, p < 0.001) to iFR and RFR. The area under the receiver curve for all measurements was 0.93 (95% confidence interval, 0.87-0.98) for QFR compared to iFR or RFR. QFR based assessment required less time with a median of 501 s (IQR 421-659 s) compared to iFR or RFR which required a median of 734 s to obtain the result (IQR 512-967 s; p < 0.001). The median use of contrast medium was similar with 21 mL (IQR 16-30 mL) for the QFR-based and 22 mL (IQR 15-35 mL) for the iFR- or RFR-based diagnostic. QFR diagnostic required less radiation. The median dose area product for QFR was 307cGycm² (IQR 151-429 cGycm² ) compared to 599 cGycm² (IQR 345-1082 cGycm² ) for iFR or RFR, p < 0.001.

CONCLUSION

QFR measurements of coronary artery blood flow correlate with iFR or RFR measurements and are associated with shorter procedure times and reduced radiation dose.

Atherosclerosis Imaging Quantitative Computed Tomography (AI-QCT) to guide referral to invasive coronary angiography in the randomized controlled CONSERVE trial

AIMS

We compared diagnostic performance, costs, and association with major adverse cardiovascular events (MACE) of clinical coronary computed tomography angiography (CCTA) interpretation versus semiautomated approach that use artificial intelligence and machine learning for atherosclerosis imaging-quantitative computed tomography (AI-QCT) for patients being referred for nonemergent invasive coronary angiography (ICA).

METHODS

CCTA data from individuals enrolled into the randomized controlled Computed Tomographic Angiography for Selective Cardiac Catheterization trial for an American College of Cardiology (ACC)/American Heart Association (AHA) guideline indication for ICA were analyzed. Site interpretation of CCTAs were compared to those analyzed by a cloud-based software (Cleerly, Inc.) that performs AI-QCT for stenosis determination, coronary vascular measurements and quantification and characterization of atherosclerotic plaque. CCTA interpretation and AI-QCT guided findings were related to MACE at 1-year follow-up.

RESULTS

Seven hundred forty-seven stable patients (60 ± 12.2 years, 49% women) were included. Using AI-QCT, 9% of patients had no CAD compared with 34% for clinical CCTA interpretation. Application of AI-QCT to identify obstructive coronary stenosis at the ≥50% and ≥70% threshold would have reduced ICA by 87% and 95%, respectively. Clinical outcomes for patients without AI-QCT-identified obstructive stenosis was excellent; for 78% of patients with maximum stenosis < 50%, no cardiovascular death or acute myocardial infarction occurred. When applying an AI-QCT referral management approach to avoid ICA in patients with <50% or <70% stenosis, overall costs were reduced by 26% and 34%, respectively.

CONCLUSIONS

In stable patients referred for ACC/AHA guideline-indicated nonemergent ICA, application of artificial intelligence and machine learning for AI-QCT can significantly reduce ICA rates and costs with no change in 1-year MACE.

Validity and correlation of quantitative flow ratio with fractional flow reserve for assessment of intermediate coronary lesions

BACKGROUND

The angiographic percent diameter stenosis (%DS) do not assess the physiological significance of epicardial coronary stenosis. The currently practised physiological indices require pressure wires with or without adenosine-induced hyperaemia. Quantitative flow ratio (QFR) is an angiography-based method to determine the functional significance of coronary stenosis. The present study aimed to analyse the diagnostic performance of QFR in comparison to fractional flow reserve (FFR) in intermediate coronary lesions.

MATERIALS AND METHODS

It was a single centre retrospective study to analyse the diagnostic performance of offline QFR with the previously performed FFR in the last six years. A total of 56 interrogated vessels were included for the analysis. Offline QFR analysis was performed and correlated with FFR values in the intermediate coronary stenoses.

RESULTS

The mean age of the study population was 62.4 ± 9.1 years, including 81% men. The left anterior descending artery (50%) was the most common analysed vessel followed by left circumflex (27%) and right coronary (21%) arteries. The mean % DS and % area stenosis were 45.25 ± 11.22% and 57.45% ± 16.25%, respectively. The mean FFR and QFR values were 0.83 ± 0.06 and 0.82 ± 0.10, respectively. A strong positive correlation was found between FFR and QFR with a Spearman correlation coefficient of 0.56. Receiver operating curve analysis for QFR and %DS with a FFR cut off value <0.80 showed an area under the curve of 0.97 and 0.77, respectively. The sensitivity, specificity and diagnostic accuracy of QFR were 87.5%, 95% and 92.8%, respectively. There was a discordance in four vessels (7.1%) between QFR and FFR.

CONCLUSION

QFR has a good diagnostic performance in comparison to the gold standard FFR for physiological assessment of intermediate lesions. Its performance is significantly better than the anatomical % DS (p < 0.001).

AI Evaluation of Stenosis on Coronary CTA, Comparison With Quantitative Coronary Angiography and Fractional Flow Reserve: A CREDENCE Trial Substudy

BACKGROUND

Clinical reads of coronary computed tomography angiography (CTA), especially by less experienced readers, may result in overestimation of coronary artery disease stenosis severity compared with expert interpretation. Artificial intelligence (AI)-based solutions applied to coronary CTA may overcome these limitations.

OBJECTIVES

This study compared the performance for detection and grading of coronary stenoses using artificial intelligence-enabled quantitative coronary computed tomography (AI-QCT) angiography analyses to core lab-interpreted coronary CTA, core lab quantitative coronary angiography (QCA), and invasive fractional flow reserve (FFR).

METHODS

Coronary CTA, FFR, and QCA data from 303 stable patients (64 ± 10 years of age, 71% male) from the CREDENCE (Computed TomogRaphic Evaluation of Atherosclerotic DEtermiNants of Myocardial IsChEmia) trial were retrospectively analyzed using an Food and Drug Administration-cleared cloud-based software that performs AI-enabled coronary segmentation, lumen and vessel wall determination, plaque quantification and characterization, and stenosis determination.

RESULTS

Disease prevalence was high, with 32.0%, 35.0%, 21.0%, and 13.0% demonstrating ≥50% stenosis in 0, 1, 2, and 3 coronary vessel territories, respectively. Average AI-QCT analysis time was 10.3 ± 2.7 minutes. AI-QCT evaluation demonstrated per-patient sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 94%, 68%, 81%, 90%, and 84%, respectively, for ≥50% stenosis, and of 94%, 82%, 69%, 97%, and 86%, respectively, for detection of ≥70% stenosis. There was high correlation between stenosis detected on AI-QCT evaluation vs QCA on a per-vessel and per-patient basis (intraclass correlation coefficient = 0.73 and 0.73, respectively; P < 0.001 for both). False positive AI-QCT findings were noted in in 62 of 848 (7.3%) vessels (stenosis of ≥70% by AI-QCT and QCA of <70%); however, 41 (66.1%) of these had an FFR of <0.8.

CONCLUSIONS

A novel AI-based evaluation of coronary CTA enables rapid and accurate identification and exclusion of high-grade stenosis and with close agreement to blinded, core lab-interpreted quantitative coronary angiography. (Computed TomogRaphic Evaluation of Atherosclerotic DEtermiNants of Myocardial IsChEmia [CREDENCE]; NCT02173275).

Influence of LDL-Cholesterol Lowering on Coronary Plaque Progression of Non-Target Lesions in Patients Undergoing Percutaneous Coronary Intervention: Findings from a Retrospective Study

The progression of NTLs after PCI accounts for a significant portion of future adverse cardiac events. The reduction in LDL-C reduces cardiovascular events. This has, however, not yet been shown in a real-world setting. We aimed to investigate the association between LDL-C changes with progression in NTLs. A total of 847 patients with successful PCI were enrolled. Patients with follow-up LDL-C ≥ 1.4 mmol/L or percent reduction <50% compared to baseline were Non-optimal group (n = 793); patients with follow-up LDL-C < 1.4 mmol/L and percent reduction ≥50% compared to baseline were Optimal group (n = 54). Compared to Non-optimal group, Optimal group presented a lower rate of NTL plaque progression (11.11% vs. 23.96%; p = 0.007) and a lower follow-up TC (2.77 ± 0.59 vs. 3.66 ± 0.97; p < 0.001) and LDL-C (1.09 ± 0.26 vs. 2.03 ± 0.71; p < 0.001). The univariate logistic regression analysis revealed that follow-up LDL-C < 1.4 mmol/L and a percent reduction ≥50% from baseline was a protective factor for NTL plaque progression (OR: 0.397; 95%CI: 0.167-0.941; p = 0.036). The multivariate logistic regression model revealed that follow-up LDL-C < 1.4 mmol/L and percent reduction ≥50% was indeed an independent factor associated with a lower rate of plaque progression of NTLs (OR: 0.398; 95% CI: 0.167-0.945; p = 0.037). Therefore, achieving guideline-recommended LDL-C level was associated with a significantly reduced risk of NTL plaque progression.

Comparison between the diagnostic performance of vessel fractional flow reserve and nonhyperemic pressure ratio for functionally significant coronary stenosis severity as assessed by fractional flow reserve

BACKGROUND

Fractional flow reserve (FFR) and nonhyperemic pressure ratios (NHPRs) have been widely used to assess the functional severity of coronary stenosis. However, their measurement requires using a pressure wire, making their use in all patients difficult. The recently developed vessel fractional flow reserve (vFFR), derived from three-dimensional quantitative coronary angiography, is expected to serve as a surrogate for pressure wire assessment.

METHODS

This retrospective study was conducted on patients with intermediate coronary stenosis who underwent FFR and NHPR measurements. The vFFR and NHPR values were compared for diagnosing coronary stenosis as defined by an FFR of ≤0.80, and the number of patients not requiring wire-based assessment was estimated.

RESULTS

In a total of 90 lesions from 74 patients (median [SD] age 75 [12] years; men 80%), the median FFR was 0.78 (0.72-0.84), and 57% of these lesions (N = 51) exhibited an FFR of ≤0.80. vFFR provided high discrimination for coronary stenosis (area under the curve 0.80, 95% confidence interval 0.70-0.90), which was comparable to that of NHPRs (p = 0.42). High diagnostic accuracy was consistently observed across a variety of clinical presentations (i.e., old age, diabetes, target coronary artery, and left ventricular hypertrophy) (p_interaction  > 0.05). In total, 55 lesions (61%) demonstrated positive or negative likelihood of coronary stenosis when vFFR was <0.73 (specificity 90%) or >0.87 (sensitivity 88%), respectively.

CONCLUSION

vFFR demonstrated excellent diagnostic performance for detecting functionally significant coronary stenosis as evaluated by FFR. vFFR may be used as a surrogate for pressure wire assessment.

Correlation of 3D Quantitative Coronary-Angiography Based Vessel FFR With Diastolic Pressure Ratio: A Single-Center Pooled Analysis of the FAST EXTEND and FAST II Studies

BACKGROUND

Vessel fractional flow reserve (vFFR) has a high diagnostic accuracy in assessing functional lesion significance compared with FFR. Nonhyperemic pressure ratios (NHPRs) were noninferior to FFR to guide revascularization of intermediate lesions. Therefore, the diagnostic performance of vFFR compared with NHPR warrants interest.

AIM

To evaluate the diagnostic performance of vFFR with a generic diastolic pressure ratio (dPR) as a reference.

METHODS

The study population was derived from the FAST EXTEND and FAST II studies. Between January 2016 and September 2020, a total of 475 patients were enrolled.

RESULTS

Median dPR was 0.92 (interquartile range [IQR], 0.87-0.95), median vFFR was 0.86 (IQR, 0.80-0.90). The sensitivity, specificity, positive and negative predictive values, and diagnostic accuracy of vFFR ≤0.80 for dPR ≤0.89 were 66%, 92%, 79%, 85%, and 84%, respectively. Vessel FFR showed a good agreement with dPR (r=0.68), consistent among specific clinical lesion subsets and a high diagnostic accuracy for dPR ≤0.89 (area under the curve=0.89). Discordance between vFFR and dPR was observed in 78/492 cases (15.6%) and logistic regression analysis did not reveal any clinical, angiographic, or hemodynamic variables associated with vFFR and dPR discordance.

CONCLUSION

Vessel FFR shows a good agreement with dPR and a high diagnostic accuracy for dPR ≤0.89.

Offline Assessment of the Quantitative Flow Ratio: Is it Useful in Clinical Practice?

INTRODUCTION

Fractional flow reserve (FFR) has been established as the gold standard in the physiological assessment of coronary obstructions severity. However, the need to insert an intracoronary pressure guidewire is a factor that limits its use. Quantitative flow ratio (QFR) is a method that infers the value of FFR from 3-dimensional quantitative coronary angiography (3D-QCA), eliminating the use of a pressure wire and coronary hyperemia. The present study aims to evaluate the diagnostic accuracy of QFR and 3D-QCA in comparison with FFR for the identification of significant obstructive coronary lesions (FFR ≤.80) and the feasibility to assess QFR in a cohort of patients without dedicated angiographic acquisition.

METHODS

Consecutive patients with coronary angiography with moderate obstructive lesions that had previous FFR measurement were evaluated. Validation of QFR was assessed by the area under the curve (AUC) and other statistical tools, using FFR as the reference method.

RESULTS

Seventy-five arteries from 69 patients were evaluated. The accuracy of the QFR to detect FFR ≤.80 was 84.0% (95% confidence interval, 75.6-92.4). The correlation and agreement between FFR and QFR were r=0.54 (P<.01) and mean difference was -0.02 ± 0.09 (P=.09), respectively. The AUC of QFR and 3D-QCA identifying stenosis >50% was 0.854 and 0.755, respectively (P=.09).

CONCLUSION

QFR demonstrated good accuracy compared with FFR for the assessment of moderate obstructive coronary lesions in an unselected clinical practice population. However, many patients were excluded from the analysis and there was no statistical difference between the receiver operator characteristic curves of the QFR and percent diameter stenosis.

Reclassification of Treatment Strategy with Fractional Flow Reserve in Cancer Patients with Coronary Artery Disease

Background and Objectives: Cancer and coronary artery disease (CAD) often coexist. Compared to quantitative coronary angiography (QCA), fractional flow reserve (FFR) has emerged as a more reliable method of identifying significant coronary stenoses. We aimed to assess the specific management, safety and outcomes of FFR-guided percutaneous coronary intervention (PCI) in cancer patients with stable CAD. Materials and Methods: FFR was used to assess cancer patients that underwent coronary angiography for stable CAD between September 2008 and May 2016, and were found to have ≥50% stenosis by QCA. Patients with lesions with an FFR > 0.75 received medical therapy alone, while those with FFR ≤ 0.75 were revascularized. Procedure-related complications, all-cause mortality, nonfatal myocardial infarction, or urgent revascularizations were analyzed. Results: Fifty-seven patients with stable CAD underwent FFR on 57 lesions. Out of 31 patients with ≥70% stenosis as measured by QCA, 14 (45.1%) had an FFR ≥ 0.75 and lesions were reclassified as moderate and did not receive PCI nor DAPT. Out of 26 patients with <70% stenosis as measured by QCA, 6 (23%) had an FFR < 0.75 and were reclassified as severe and were treated with PCI and associated DAPT. No periprocedural complications, urgent revascularization, acute coronary syndromes, or cardiovascular deaths were noted. There was a 22.8% mortality at 1 year, all cancer related. Patients who received a stent by FFR assessment showed a significant association with decreased risk of all-cause death (HR: 0.37, 95% CI 0.15−0.90, p = 0.03). Conclusions: Further studies are needed to define the optimal therapeutic approach for cancer patients with CAD. Using an FFR cut-off point of 0.75 to guide PCI translates into fewer interventions and can facilitate cancer care. There was an overall reduction in mortality in patients that received a stent, suggesting increased resilience to cancer therapy and progression.

Pressure- and 3D-Derived Coronary Flow Reserve with Hydrostatic Pressure Correction: Comparison with Intracoronary Doppler Measurements

Purpose: To develop a method of coronary flow reserve (CFR) calculation derived from three-dimensional (3D) coronary angiographic parameters and intracoronary pressure data during fractional flow reserve (FFR) measurement. Methods: Altogether 19 coronary arteries of 16 native and 3 stented vessels were reconstructed in 3D. The measured distal intracoronary pressures were corrected to the hydrostatic pressure based on the height differences between the levels of the vessel orifice and the sensor position. Classical fluid dynamic equations were applied to calculate the flow during the resting state and vasodilatation based on morphological data and intracoronary pressure values. 3D-derived coronary flow reserve (CFRp-3D) was defined as the ratio between the calculated hyperemic and the resting flow and was compared to the CFR values simultaneously measured by the Doppler sensor (CFRDoppler). Results: Haemodynamic calculations using the distal coronary pressures corrected for hydrostatic pressures showed a strong correlation between the individual CFRp-3D values and the CFRDoppler measurements (r = 0.89, p < 0.0001). Hydrostatic pressure correction increased the specificity of the method from 46.1% to 92.3% for predicting an abnormal CFRDoppler < 2. Conclusions: CFRp-3D calculation with hydrostatic pressure correction during FFR measurement facilitates a comprehensive hemodynamic assessment, supporting the complex evaluation of macro-and microvascular coronary artery disease.

Determinants of visual-functional mismatches as assessed by coronary angiography and quantitative flow ratio

OBJECTIVE

We aimed to evaluate the determinants of visual-functional mismatches between quantitative coronary angiography (QCA) and the quantitative flow ratio (QFR).

BACKGROUND

The fractional flow reserve (FFR) has been established as a method to estimate the functional stenosis severity of coronary artery disease and to optimize decision-making for revascularization. The QFR is a novel angiography-derived computational index that can estimate the FFR without pharmacologically induced hyperemia or the use of pressure wire.

METHODS

A total of 504 de novo intermediate-to-severe stable lesions that underwent angiographic and physiological assessments were analyzed. All lesions were divided into four groups based on the significance of visual (QCA-diameter stenosis [DS] > 50% and ≤ 50%) and functional (QFR ≤ 0.80 and > 0.80) stenosis severity. Patient characteristics, angiographic findings, and physiological indices were compared.

RESULTS

One-hundred seventy-eight lesions (35.3%) showed discordant visual-functional assessments; mismatch (QCA-DS > 50% and QFR > 0.80) in 75 lesions (14.9%) and reverse mismatch (QCA-DS ≤ 50% and QFR ≤ 0.80) in 103 lesions (20.4%), respectively. Reverse mismatch was associated with non-diabetes, lower ejection fraction, higher Duke jeopardy score, and lower coronary flow reserve (CFR). Mismatch was associated with smaller QCA-DS, larger reference diameter, shorter lesion length, lower Duke jeopardy score, and higher CFR. Lesion location and microcirculatory resistance was not associated with the prevalence of mismatches. Reverse mismatch group had the higher prevalence of discordant decision-makings between QFR and FFR than the other three groups.

CONCLUSIONS

The CFR and subtended myocardial mass were predictors of visual-functional mismatches between QCA-DS and the QFR. Caution should be exercised in lesions showing QCA-DS/QFR reverse mismatch.

Imaging and 2-year clinical outcomes of thin strut sirolimus-eluting bioresorbable vascular scaffold: The MeRes-1 extend trial

OBJECTIVES

This study explores the safety and efficacy of thin strut MeRes100 sirolimus-eluting bioresorbable vascular scaffold (BRS) in patients with de novo coronary artery lesions.

BACKGROUND

In interventional cardiology, the emergence of BRS technology is catalyzing the next paradigm shift.

METHODS

The MeRes-1 Extend was a multicenter, prospective, single-arm, open-label study enrolling 64 patients in Spain, Macedonia, Brazil, South Africa, Malaysia, and Indonesia. The safety endpoint was major adverse cardiac events (MACE) which composed of cardiac death, myocardial infarction (MI), and ischemia-driven target lesion revascularization (ID-TLR). The imaging efficacy endpoint was mean in-scaffold late lumen loss (LLL) evaluated by quantitative coronary angiography (QCA). Optical coherence tomography (OCT) imaging was performed at baseline and 6-month follow-up.

RESULTS

A total of 69 target lesions were identified in 64 enrolled patients (mean age 58.30 ± 9.02 years). Of the treated lesions, 49 (71.01%) lesions were of type B2/C. Procedural and device success was achieved in 64 and 62 patients, respectively. At 2-year follow-up, MACE was reported in one patient (1.61%) in the form of ID-TLR. There was no case of MI, cardiac death or scaffold thrombosis through 2-year. In a subset of 32 patients, paired QCA showed mean in-scaffold LLL of 0.18 ± 0.31 mm at 6-month follow-up. In a subset of 21 patients, OCT revealed 97.95 ± 3.69% strut coverage with mean scaffold area of 7.56 ± 1.79 mm² and no evidence of strut malapposition.

CONCLUSIONS

The clinical and imaging outcomes of MeRes-1 Extend trial demonstrated favorable safety and efficacy of MeRes100 sirolimus-eluting BRS in patients with de novo coronary artery lesions.

Impact of physiologically diffuse versus focal pattern of coronary disease on quantitative flow reserve diagnostic accuracy

Background

Fractional flow reserve (FFR) and instantaneous wave‐free ratio (iFR) disagree in about 20% of intermediate coronary lesions. As the physiological pattern of coronary artery disease has a significant influence on FFR‐iFR discordance, we sought to assess it may impact on the diagnostic accuracy of quantitative flow reserve (QFR).

Methods

One hundred and ninety‐four patients with 224 intermediate coronary lesions were investigated with iFR, FFR, and QFR. The physiological pattern of disease was assessed with iFR Scout pullback and QFR virtual pullback in all the cases.

Results

A predominantly physiologically focal pattern was observed in 81 (36.2%) lesions, whereas a predominantly physiologically diffuse was observed in 143 (63.8%) cases. QFR demonstrated a significant correlation (r = 0.581, p < 0.001) and a substantial agreement with iFR, both in diffuse (AUC = 0.798) and in focal (AUC = 0.812) pattern of disease. Discordance between QFR and iFR was observed in 51 (22.8%) lesions, consisting of iFR+/QFR− (64.7%) and iFR−/QFR+ (35.3%). Notably, the physiological pattern of disease was the only variable significantly associated with iFR/QFR discordance. QFR virtual pullback demonstrated an excellent agreement (83.9%) with iFR Scout pullback in classifying the physiological pattern of disease.

Conclusions

QFR has a good diagnostic accuracy in assessing myocardial ischemia independently of the pattern of coronary disease. However, the physiological pattern of disease has an influence on the QFR/iFR discordance, which occurs in ~20% of the cases. The QFR virtual pullback correctly defined the physiological pattern of disease in the majority of the cases using the iFR pullback as reference.

Elastic stent recoil in coronary total occlusions: Comparison of durable-polymer zotarolimus eluting stent and ultrathin strut bioabsorbable-polymer sirolimus eluting stent

Objectives

To compare stent recoil (SR) of the thin‐strut durable‐polymer Zotarolimus‐eluting stent (dp‐ZES) and the ultrathin‐strut bioabsorbable‐polymer Sirolimus‐eluting stent (bp‐SES) in chronic total occlusions (CTOs) and to investigate the predictors of high SR in CTOs.

Background

Newer ultrathin drug eluting stent might be associated with lower radial force and higher elastic recoil due to the thinner strut design, possibly impacting on the rate of in‐stent restenosis and thrombosis.

Methods

Between January 2017 and November 2019, consecutive patients with CTOs undergoing percutaneous coronary intervention were evaluated. Only patients treated with dp‐ZES or bp‐SES were included and stratified accordingly. Quantitative coronary angiography analysis was used to assess absolute SR, relative SR, absolute focal SR, relative focal SR, high absolute, and high relative focal SR.

Results

A total of 128 lesions (67 treated with dp‐ZES and 61 with bp‐SES) in 123 patients were analyzed. Between bp‐SES and dp‐ZES no differences were found in absolute SR (p = .188), relative SR (p = .138), absolute focal SR (p = .069), and relative focal SR (p = .064). High absolute and high relative focal SR occurred more frequently in bp‐SES than in dp‐ZES (p = .004 and p = .015). Bp‐SES was a predictor of high absolute focal SR (Odds ratio [OR] 3.29, 95% confidence interval [CI] 1.50–7.22, p = .003]. High‐pressure postdilation and bp‐SES were predictors of high relative focal SR (OR 2.22, 95% CI 1.01–4.86, p = .047; OR 2.74, 95% CI 1.24–6.02, p = .012, respectively).

Conclusions

Both stents showed an overall low SR. However, ultra‐thin strut bp‐SES was a predictor of high absolute and high relative focal SR.

Prognostic value of quantitative flow ratio measured immediately after drug-coated balloon angioplasty for in-stent restenosis

OBJECTIVES

This study aimed to evaluate prognostic value of quantitative flow ratio (QFR) in drug-coated balloon (DCB) angioplasty for in-stent restenosis (ISR).

BACKGROUND

There is a high incidence of recurrent ISR after DCB angioplasty. QFR is a novel method for fast computation of fractional flow reserve for the target vessel based on quantitative coronary angiography (QCA) and fluid dynamics algorithms.

METHODS

Patients participating in the RESTORE ISR China randomized trial were enrolled and classified into the recurrent restenosis group and the non-recurrent restenosis group. The binary classifications followed the QCA standards of ISR. Clinical and angiographic characteristics of the groups were analyzed, and the QFRs before and after lesion preparation and after final DCB angioplasty were measured and compared.

RESULTS

A total of 208 patients who underwent follow-up angiography were enrolled in the study, with 226 lesions measured in total. QFR value after DCB angioplasty (odds ratio [OR] 0.88; 95% confidence interval [CI] 0.83-0.93; p < .0001 for 1 mm increase), lesion length (OR: 1.08; 95% CI: 1.01-1.15; p = .017), and vessel caliber lumen diameter (OR: 0.35; 95% CI 0.13-0.89; p = .027) were independently associated with recurrent restenosis after DCB angioplasty. The optimal QFR cut-off value was determined to be 0.90 with a sensitivity of 0.94, specificity of 0.56, and accuracy of 0.79 in predicting recurrent restenosis.

CONCLUSIONS

The QFR value after DCB angioplasty is a promising predictor of DES ISR.

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.

Referral of patients for fractional flow reserve using quantitative flow ratio

AIMS

Quantitative flow ratio (QFR) is a recently developed technique to calculate fractional flow reserve (FFR) based on 3D quantitative coronary angiography and computational fluid dynamics, obviating the need for a pressure-wire and hyperaemia induction. QFR might be used to guide patient selection for FFR and subsequent percutaneous coronary intervention (PCI) referral in hospitals not capable to perform FFR and PCI. We aimed to investigate the feasibility to use QFR to appropriately select patients for FFR referral.

METHODS AND RESULTS

Patients who underwent invasive coronary angiography in a hospital where FFR and PCI could not be performed and were referred to our hospital for invasive FFR measurement, were included. Angiogram images from the referring hospitals were retrospectively collected for QFR analysis. Based on QFR cut-off values of 0.77 and 0.86, our patient cohort was reclassified to 'no referral' (QFR ≥0.86), referral for 'FFR' (QFR 0.78-0.85), or 'direct PCI' (QFR ≤0.77). In total, 290 patients were included. Overall accuracy of QFR to detect an invasive FFR of ≤0.80 was 86%. Based on a QFR cut-off value of 0.86, a 50% reduction in patient referral for FFR could be obtained, while only 5% of these patients had an invasive FFR of ≤0.80 (thus, these patients were incorrectly reclassified to the 'no referral' group). Furthermore, 22% of the patients that still need to be referred could undergo direct PCI, based on a QFR cut-off value of 0.77.

CONCLUSION

QFR is feasible to use for the selection of patients for FFR referral.

Validation of novel 3-dimensional quantitative coronary angiography based software to calculate fractional flow reserve post stenting

Objectives

To validate novel dedicated 3D‐QCA based on the software to calculate post PCI vessel‐FFR (vFFR) in a consecutive series of patients, to assess the diagnostic accuracy, and to assess inter‐observer variability.

Background

Low post percutaneous coronary intervention (PCI) fractional flow reserve (FFR) predicts future adverse cardiac events. However, FFR assessment requires the insertion of a pressure wire in combination with the use of a hyperemic agent.

Methods

FAST POST study is an observational, retrospective, single‐center cohort study. One hundred patients presenting with stable angina or non ST‐elevation myocardial infarction, who underwent post PCI FFR assessment using a dedicated microcatheter were included. Two orthogonal angiographic projections were acquired to create a 3D reconstruction of the coronary artery using the CAAS workstation 8.0. vFFR was subsequently calculated using the aortic root pressure.

Results

Mean age was 65±12 years and 70% were male. Mean microcatheter based FFR and vFFR were 0.91±0.07 and 0.91±0.06, respectively. A good linear correlation was found between FFR and vFFR (r = 0.88; p <.001). vFFR had a higher accuracy in the identification of patients with FFR values <0.90, AUC 0.98 (95% CI: 0.96‐1.00) as compared with 3D‐QCA AUC 0.62 (95% CI: 0.94‐0.74). Assessment of vFFR had a low inter‐observer variability (r = 0.95; p <.001).

Conclusion

3D‐QCA derived post PCI vFFR correlates well with invasively measured microcatheter based FFR and has a high diagnostic accuracy to detect FFR <0.90 with low inter‐observer variability.

Comparison of three-dimensional quantitative coronary angiography and intravascular ultrasound for detecting functionally significant coronary lesions

Background

Three-dimensional quantitative coronary angiography (3D-QCA) can provide more accurate measurement of true vessel size and may be comparable to intravascular ultrasound (IVUS) in identifying functionally significant coronary stenosis, as determined by fractional flow reserve (FFR). This study aimed to evaluate the diagnostic accuracy of 3D-QCA for predicting FFR <0.8.

Methods

We assessed 175 lesions in 175 patients by FFR, IVUS, and 3D-QCA. Correlations between 3D-QCA values, IVUS values, and FFR values were analyzed. Receiver operating characteristic (ROC) curves were used to evaluate diagnostic accuracy of 3D-QCA for predicting FFR <0.8 and to determine the appropriate cut-off value.

Results

Upon evaluating 3D-QCA values, minimum lumen area (MLA) correlated with FFR value (r=0.48, P<0.001). Considering IVUS values, MLA correlated with FFR value (r=0.43, P<0.001). Also, 3D-QCA MLA was well correlated with IVUS MLA (r=0.61, P<0.001). The area under the ROC curve (AUC) for 3D-QCA MLA was 0.77, and the best cut-off value was 2.37 (sensitivity: 73%, specificity: 71%). The AUC for IVUS MLA was 0.73, and the best cut-off value was 3.01 (sensitivity: 71%, specificity: 65%). There was no significant difference in AUC for 3D-MLA and IVUS-MLA (P=0.27).

Conclusions

3D-QCA is not inferior to IVUS for functional assessment of intermediate coronary lesions. We can consider 3D-QCA as a suitable substitute for IVUS or FFR in determining coronary intervention.

Clinical effectiveness and radial artery remodeling assessment via very-high-frequency ultrasound/ultra biomicroscopy after applying slender 7Fr sheath for transradial approach in left main bifurcation disease

OBJECTIVE

To explore the clinical effect and radial remodeling of transradial slender 7 Fr sheath for left main bifurcation disease (LM bifurcation).

METHODS

From January 2018 to September 2019, 236 patients with LM bifurcation undergoing transradial percutaneous coronary intervention (PCI) from two heart centers were divided into slender 7 Fr sheath group (n = 127) and 6 Fr sheath group (n = 109). Quantitative coronary angiography (QCA) and very high-frequency ultrasound/ultra biomicroscopy (VHFUBM) were used to assess the clinical effect and radial remodeling of transradial sheath.

RESULTS

Slender 7 Fr sheath group had a higher preoperative distal bifurcation angle (67.271 ± 22.886) than 6 Fr group (55.831 ± 20.245) (p < .05). Post-PCI QCA results showed significant differences in minimum lumen diameter at proximal left anterior descending artery (LAD) and left circumflex artery (LCX) between two groups (p < .05). There were no significant differences in target vessel myocardial infarction, target vessel revascularization, death and major adverse cardiocerebrovascular events (MACCE) at 30-day and 1-year follow-up between two groups (p>.05). No significant differences were observed in radial artery diameter (RAD), intimal-medial thickness (IMT) and radial artery injury at 24-h and 90-day follow-up between two groups.

CONCLUSION

With larger main and side branch diameter, larger angle of bifurcation and higher SYNTAX score, transradial slender 7 Fr sheath obtained similar clinical effects as 6 Fr sheath without increasing the occurrence of adverse events. Similar follow-up RAD, IMT and radial artery injury were observed. Therefore, slender 7 Fr sheath has safety and feasibility in applying to transradial LM-Bifurcation PCI.