Expert consensus statement on the use of fractional flow reserve, intravascular ultrasound, and optical coherence tomography: a consensus statement of the Society of Cardiovascular Angiography and Interventions

Cardiovascular outcomes of complex bifurcation lesions following double kissing crush or nano-crush techniques: The multicenter EVOLUTE-CRUSH V study

BACKGROUND

Double kissing crush (DKC) and nano-crush (NC) techniques are frequently used, but the comparison for both techniques is still lacking. The goal of this multicenter study was to retrospectively assess the midterm clinical results of DKC and NC stenting in patients with complex bifurcation lesions (CBLs).

METHODS

A total of 324 consecutive patients [male: 245 (75.6%), mean age: 60.73 ± 10.21 years] who underwent bifurcation percutaneous coronary intervention between January 2019 and May 2023 were included. The primary endpoint defined as the major cardiovascular events (MACE) included cardiac death, target vessel myocardial infarction (TVMI), or clinically driven target lesion revascularization (TLR). Inverse probability weighting (IPW) was performed to reduce treatment selection bias. This is the first report comparing the clinical outcomes of DKC and NC stenting in patients with CBL.

RESULTS

The initial revascularization strategy was DKC in 216 (66.7%) cases and NC in 108 (33.3%) patients. SYNTAX scores [25.5 ± 6.73 vs. 23.32 ± 6.22, p = 0.005] were notably higher in the NC group than the DKC group. The procedure time (76.98 ± 25.1 vs. 57.5 ± 22.99 min, p = 0.001) was notably higher in the DKC group. The incidence of MACE (18.5 vs. 9.7%, p = 0.025), clinically driven TLR (14.8 vs. 6%, p = 0.009), and TVMI (10.2 vs. 4.2%, p = 0.048) were notably higher in the NC group than in the DKC group. The midterm MACE rate in the overall population notably differed between the NC group and the DKC group (adjusted HR (IPW): 2.712, [95% CI: 1.407-5.228], p = 0.003).

CONCLUSION

In patients with CBLs, applying the DKC technique for bifurcation treatment had better ischemia-driven outcomes than the NC technique.

Late Outcomes of Patients in the Emergency Department With Acute Chest Pain Evaluated With Computed Tomography-Derived Fractional Flow Reserve

Computed tomography (CTA)-derived fractional flow reserve (FFRCT) guides the need for invasive coronary angiography (ICA). Late outcomes after FFRCT are reported in stable ischemic heart disease but not in acute chest pain in the emergency department (ACP-ED). The objectives are to assess the risk of death, myocardial infarction (MI), revascularization, and ICA after FFRCT. From 2015 to 2018, 389 low-risk patients with ACP-ED (negative biomarkers, no electrocardiographic ischemia) underwent CTA and FFRCT and were entered into a prospective institutional registry; patients were followed up for 41 ± 10 months. CTA stenosis ≥50% was present in 81% of the patients. Positive (FFRCT ≤0.80) and negative FFRCT were observed in 124 (32%) and 265 patients (68%), respectively. ICA was performed in 108 of 124 patients (87%) with positive FFRCT and 89 of 265 patients (34%) with negative FFRCT (p <0.00001). Revascularization was performed in 87 of 124 (70%) patients with positive FFRCT and in 22 of 265 (8%) with negative FFRCT (p <0.00001). Appropriateness of revascularization was established by blinded adjudication of ICA and invasive FFR using practice guidelines; revascularization was appropriate in 81 of 124 (65%) and 6 of 265 (2%) of FFRCT-positive and -negative patients, respectively (p <0.00001). At follow-up, for patients with positive versus negative FFRCT, the rates were 0.8% versus 0% for death (p = 0.32) and 1.6% versus 0.4% for MI (p = 0.24). In conclusion, in low-risk patients with ACP-ED who underwent CTA and FFRCT, the risk of late death (0.2%) and MI (0.7%) are low. Negative FFRCT is associated with excellent long-term prognosis, and positive FFRCT predicts obstructive disease requiring revascularization. FFRCT can safely triage patients with ACP-ED and reduce unnecessary ICA and revascularization.

Long-term cardiovascular outcomes after mini-crush or T and minimal protrusion techniques in complex bifurcation lesions: the EVOLUTE-CRUSH III study

BACKGROUND

Mini-crush (MC) and T-stenting and small protrusion (TAP) techniques are frequently used, but the long-term comparison of both techniques in patients with complex bifurcation lesions (CBLs) is still a debatable issue. This study sought to retrospectively evaluate the long-term outcomes of MC and TAP techniques in patients with CBLs.

METHODS

A total of 271 patients [male: 202 (78.9%), mean age: 58.90 ± 10.11 years] patients in whom complex bifurcation intervention was performed between 2014 and 2023 were involved. The primary endpoint was major cardiovascular events (MACE) as the combination of cardiac death, target vessel myocardial infarction, or clinically driven-target lesion revascularization. The Cox proportional hazard models were adjusted by the inverse probability weighting approach to reduce treatment selection bias.

RESULTS

The initial management strategy was MC in 146 patients and TAP in 125 cases. MACE occurred in 52 patients (19.2%) during a mean follow-up period of 32.43 ± 16 months. The incidence of MACE (13 vs. 26.4%, P = 0.005) and major cardiovascular and cerebral events (15.1 vs. 28.8%, P = 0.006) were significantly lower in the MC group than in the TAP group. Additionally, the incidence of definite or probable stent thrombosis was numerically lower in the MC group compared with the TAP group but did not differ significantly (2.7 vs. 8%, P = 0.059). The long-term MACE was notably higher in the TAP group than the MC group [adjusted hazard ratio (inverse probability weighted): 1.936 (95% confidence interval: 1.053-3.561), P = 0.033].

CONCLUSION

In this study involving patients with CBLs, percutaneous coronary intervention with the MC technique had better long-term outcomes than the TAP technique.

Long-term outcomes following double kissing crush or mini-culotte stenting for complex coronary bifurcation lesions: the EVOLUTE-CRUSH IV study

BACKGROUND

This study aimed to evaluate the long-term outcomes of double kissing crush stenting (DKC) and mini-culotte technique (MCT) in patients with complex bifurcation lesions.

METHODS

This retrospective study enrolled 236 patients who underwent percutaneous coronary intervention (PCI) for complex coronary bifurcation disease between January 2014 and November 2022. The primary endpoint was target lesion failure (TLF), defined as the combination of cardiac death, myocardial infarction (MI), or clinically driven target lesion revascularization (TLR). The secondary endpoint was major cardiovascular and cerebral events (MACCE) including all-cause death, MI, TLR, stroke, or stent thrombosis. The regression models were adjusted by applying the inverse probability weighted (IPW) approach to reduce treatment selection bias.

RESULTS

The initial management strategy was DKC in 154 (65.3%) patients and MCT in 82 (34.7%) patients (male: 194 [82.2%], mean age: 60.85 ± 10.86 years). The SYNTAX scores were similar in both groups. The rates of long-term TLF and MACCE rates were 17.4% and 20%, respectively. The rate of TLF (26.8% vs. 12.3%, p = 0.005) was higher in patients treated with MCT than those treated with the DKC technique, mainly driven by more frequent TLR (15.9% vs. 7.1%, p = 0.035). The long-term TLF and MACCE rates were notably lower in the DKC group compared to the others: adjusted hazard ratio (HR; IPW): 0.407, p = 0.009 for TLF, and adjusted HR(IPW): 0.391 [95% CI: 0.209-0.730], p = 0.003 for MACCE.

CONCLUSION

At long-term follow-up, the rates of TLF and MACCE were 17.4% and 20%, respectively. However, long-term TLF was significantly higher in patients treated with MCT than those treated with the DKC technique, primarily due to a more frequent occurrence of clinically driven TLR.

Comparison of long-term outcomes of double kissing crush versus T and minimal protrusion techniques in complex bifurcation lesions: The EVOLUTE-CRUSH II registry

BACKGROUND

Double kissing (DK)-crush and T-stenting and small protrusion (TAP) techniques are gaining popularity, but the comparison for both techniques is still lacking. This study sought to retrospectively evaluate the long-term outcomes of DK-crush and TAP techniques in patients with complex bifurcation lesions.

METHODS

A total of 255 (male: 205 [80.3%], mean age: 59.56 ± 10.13 years) patients who underwent coronary bifurcation intervention at a single-center between January 2014 and May 2021 were included. Angiographic features, procedure details, and in-hospital or long-term outcomes were assessed. The primary endpoint was target lesion failure (TLF), defined as the combination of cardiac death, target vessel myocardial infarction, or clinically driven-target lesion revascularization (TLR). The regression models were adjusted applying by the inverse probability weighted (IPW) approach to reduce treatment selection bias.

RESULTS

The initial management strategy was DK-crush in 152 (59.6%) patients and TAP in 103 (40.4%) cases. The SYNTAX scores (24.58 ± 7.4 vs. 24.26 ± 6.39, p = 0.846) were similar in both groups. The number of balloon (6.32 ± 1.82 vs. 3.92 ± 1.19, p < 0.001) usage was significantly higher in the DK-crush group than in the TAP group. The rates of TLF (11.8 vs. 22.3%, p = 0.025) and clinically driven TLR (6.6 vs. 15.5%, p = 0.020) were significantly lower in the DK-crush group compared to the TAP group. The long-term TLF was significantly higher in the TAP group compared to the DK-crush group (unadjusted HR: 1.974, [95% CI: 1.044-3.732], p = 0.035 and adjusted HR [IPW]: 2.498 [95% CI: 1.232-5.061], p = 0.011).

CONCLUSION

The present study showed that the DK-crush technique of bifurcation treatment was associated with lower long-term TLF and TLR rates compared to the TAP technique.

Computed Tomography-Derived Physiology Assessment: State-of-the-Art Review

Coronary computed tomography angiography (CCTA) and CCTA-derived fractional flow reserve (FFRCT) are the best non-invasive techniques to assess coronary artery disease (CAD) and myocardial ischemia. Advances in these technologies allow a paradigm shift to the use of CCTA and FFRCT for advanced plaque characterization and planning myocardial revascularization.

Contemporary Use of Coronary Physiology in Cardiology

Coronary angiography has a limited ability to predict the functional significance of intermediate coronary lesions. Hence, physiological assessment of coronary lesions, via fractional flow reserve (FFR) or instantaneous wave-free ratio (iFR), has been introduced to determine their functional significance. An accumulating body of evidence has consolidated the role of physiology-guided revascularization, particularly among patients with stable ischemic heart disease. The use of FFR or iFR to guide decision-making in patients with stable ischemic heart disease and intermediate coronary lesions received a class I recommendation from major societal guidelines. Nevertheless, the role of coronary physiology testing is less clear among certain patients' groups, including patients with serial coronary lesions, acute coronary syndromes, aortic stenosis, heart failure, as well as post-percutaneous coronary interventions. In this review, we aimed to discuss the utility and clinical evidence of coronary physiology (mainly FFR and iFR), with emphasis on those specific patient groups.

Long-Term Evaluation of Revascularization Strategies for Medina 0.1.0 Left Main Bifurcation Lesions: The LM-CROSSOVER Registry

The present study aimed to compare long-term outcomes of patients with Medina 0.1.0 left main (LM) bifurcation lesions treated by crossover stenting (COS) versus accurate ostial stenting (AOS). A total of 229 consecutive eligible patients with Medina 0.1.0 LM bifurcation lesions were enrolled and were stratified according to the stenting techniques. The primary end-point was major cardiovascular and cerebral events (MACCE), defined as the combination of all-cause death, target vessel related-myocardial infarction (MI), clinically driven target lesion revascularization (TLR), stroke, or stent thrombosis. COS and AOS were applied to 78 (34%) and 151 (66%) patients, respectively. During a mean of 40.6 ± 21.1 months of follow-up, the rate of MACCE (27.8 vs 12.8%; P=.007) was higher in patients treated with AOS than those treated with the COS technique, mainly driven by more frequent all-cause death (13.9 vs 3.8%, P = .013) and TLR (6.4 vs 15.9%; P = .029). In multivariable Cox regression analysis, AOS strategy was one of the independent predictors of MACCE (odds ratio: 2.166; 95% confidence interval, 1.080-4.340; P = .029). The current study suggests that COS was associated with a better long-term MACCE rate and lower all-cause mortality rate than AOS in patients with Medina 0.1.0 LM bifurcation disease.

Comprehensive Computed Tomography Imaging of Vessel-specific and Lesion-specific Myocardial Ischemia

Coronary computed tomographic angiography (CCTA) has emerged as a fast and robust tool with high sensitivity and excellent negative predictive value for the evaluation of coronary artery disease, but is unable to estimate the hemodynamic significance of a lesion. Advances in computed tomography (CT)-based diagnostic techniques, for example, CT-derived fractional flow reserve and CT perfusion, have helped transform CCTA primarily from an anatomic assessment tool to a technique that is able to provide both anatomic and functional information for a stenosis. With the results of the ISCHEMIA trial published in 2019, these advanced techniques can elevate CCTA into the role of a better gatekeeper for decision-making and can help guide referral for invasive management. In this article, we review the principles, limitations, diagnostic performance, and clinical utility of these 2 functional CT-based techniques in the evaluation of vessel-specific and lesion-specific ischemia.

Intravascular Imaging versus Physiological Assessment versus Biomechanics-Which Is a Better Guide for Coronary Revascularization

Today, coronary artery disease (CAD) continues to be a prominent cause of death worldwide. A reliable assessment of coronary stenosis represents a prerequisite for the appropriate management of CAD. Nevertheless, there are still major challenges pertaining to some limitations of current imaging and functional diagnostic modalities. The present review summarizes the current data on invasive functional and intracoronary imaging assessment using optical coherence tomography (OCT), and intravascular ultrasound (IVUS). Amongst the functional parameters-on top of fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR)-we point to novel angiography-based measures such as quantitative flow ratio (QFR), vessel fractional flow reserve (vFFR), angiography-derived fractional flow reserve (FFRangio), and computed tomography-derived flow fractional reserve (FFR-CT), as well as hybrid approaches focusing on optical flow ratio (OFR), computational fluid dynamics and attempts to quantify the forces exaggerated by blood on the coronary plaque and vessel wall.

Detecting lesion-specific ischemia in patients with coronary artery disease with computed tomography fractional flow reserve measured at different sites

OBJECTIVES

Whether a stenosis can cause hemodynamic lesion-specific ischemia is critical for the treatment decision in patients with coronary artery disease (CAD). Based on coronary computed tomography angiography (CCTA), CT fractional flow reserve (FFR_CT) can be used to assess lesion-specific ischemia. The selection of an appropriate site along the coronary artery tree is vital for measuring FFR_CT. However the optimal site to measure FFR_CT for a target stenosis remains to be adequately determined. The purpose of this study was to determine the optimal site to measure FFR_CT for a target lesion in detecting lesion-specific ischemia in CAD patients by evaluating the performance of FFR_CT measured at different sites distal to the target lesion in detecting lesion-specific ischemia with FFR measured with invasive coronary angiography (ICA) as reference standard.

METHODS

In this single-center retrospective cohort study, a total of 401 patients suspected of having CAD underwent invasive ICA and FFR between March 2017 and December 2021 were identified. 52 patients having both CCTA and invasive FFR within 90 days were enrolled. Patients with vessels 30%-90% diameter stenosis as determined by ICA were referred to invasive FFR evaluation, which was performed 2-3 cm distal to the stenosis under the condition of hyperemia. For each vessel with 30%-90% diameter stenosis, if only one stenosis was present, this stenosis was selected as the target lesion; if serial stenoses were present, the stenosis most distal to the vessel end was chosen as the target lesion. FFR_CT was measured at four sites: 1 cm, 2 cm, and 3 cm distal to the lower border of the target lesion (FFR_CT-1 cm, FFR_CT-2 cm, FFR_CT-3 cm), and the lowest FFR_CT at the distal vessel tip (FFR_CT-lowest). The normality of quantitative data was assessed using the Shapiro-Wilk test. Pearson's correlation analysis and Bland-Altman plots were used for assessing the correlation and difference between invasive FFR and FFR_CT. Correlation coefficients derived from Chi-suqare test were used to assess the correlation between invasive FFR and the cominbaiton of FFR_CT measred at four sites. The performances of significant obstruction stenosis (diameter stenosis ≥ 50%) at CCTA and FFR_CT measured at the four sites and their combinations in diagnosing lesion-specific ischemia were evaluated by receiver-operating characteristic (ROC) curves using invasive FFR as the reference standard. The areas under ROC curves (AUCs) of CCTA and FFR_CT were compared by the DeLong test.

RESULTS

A total of 72 coronary arteries in 52 patients were included for analysis. Twenty-five vessels (34.7%) had lesion-specific ischemia detected by invasive FFR and 47 vesseles (65.3%) had no lesion-spefifice ischemia. Good correlation was found between invasive FFR and FFR_CT-2 cm and FFR_CT-3 cm (r = 0.80, 95% CI, 0.70 to 0.87, p < 0.001; r = 0.82, 95% CI, 0.72 to 0.88, p < 0.001). Moderate correlation was found between invasive FFR and FFR_CT-1 cm and FFR_CT-lowest (r = 0.77, 95% CI, 0.65 to 0.85, p < 0.001; r = 0.78, 95% CI, 0.67 to 0.86, p < 0.001). FFR_CT-1 cm + FFR_CT-2 cm, FFR_CT-2 cm + FFR_CT-3 cm, FFR_CT-3 cm + FFR_CT-lowest, FFR_CT-1 cm + FFR_CT-2 cm + FFR_CT-3 cm, and FFR_CT-2 cm + FFR_CT-3 cm + FFR_CT-lowest were correatled with invasive FFR (r = 0.722; 0.722; 0.701; 0.722; and 0.722, respectively; p < 0.001 for all). Bland-Altman plots revealed a mild difference between invasive FFR and the four FFR_CT (invasive FFR vs. FFR_CT-1 cm, mean difference -0.0158, 95% limits of agreement: -0.1475 to 0.1159; invasive FFR vs. FFR_CT-2 cm, mean difference 0.0001, 95% limits of agreement: -0.1222 to 0.1220; invasive FFR vs. FFR_CT-3 cm, mean difference 0.0117, 95% limits of agreement: -0.1085 to 0.1318; and invasive FFR vs. FFR_CT-lowest, mean difference 0.0343, 95% limits of agreement: -0.1033 to 0.1720). AUCs of CCTA, FFR_CT-1 cm, FFR_CT-2 cm, FFR_CT-3 cm, and FFR_CT-lowest in detecting lesion-specific ischemia were 0.578, 0.768, 0.857, 0.856 and 0.770, respectively. All FFR_CT had a higher AUC than CCTA (all p < 0.05), FFR_CT-2 cm achieved the highest AUC at 0.857. The AUCs of FFR_CT-2 cm and FFR_CT-3 cm were comparable (p > 0.05). The AUCs were similar between FFR_CT-1 cm + FFR_CT-2 cm, FFR_CT-3 cm + FFR_CT-lowest and FFR_CT-2 cm alone (AUC = 0.857, 0.857, 0.857, respectively; p > 0.05 for all). The AUCs of FFR_CT-2 cm + FFR_CT-3 cm, FFR_CT-1 cm + FFR_CT-2 cm + FFR_CT-3 cm, FFR_CT-and 2 cm + FFR_CT-3 cm + FFR_CT-lowest (0.871, 0.871, 0.872, respectively) were slightly higher than that of FFR_CT-2 cm alone (0.857), but without significnacne differences (p > 0.05 for all).

CONCLUSIONS

FFR_CT measured at 2 cm distal to the lower border of the target lesion is the optimal measurement site for identifying lesion-specific ischemia in patients with CAD.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Incremental diagnostic value of radiomics signature of pericoronary adipose tissue for detecting functional myocardial ischemia: a multicenter study

OBJECTIVES

To determine the incremental diagnostic value of radiomics signature of pericoronary adipose tissue (PCAT) in addition to the coronary artery stenosis and plaque characters for detecting hemodynamic significant coronary artery disease (CAD) based on coronary computed tomography angiography (CCTA).

METHODS

In a multicenter trial of 262 patients, CCTA and invasive coronary angiography were performed, with fractional flow reserve (FFR) in 306 vessels. A total of 13 conventional quantitative characteristics including plaque characteristics (N = 10) and epicardial adipose tissue characteristics (N = 3) were obtained. A total of 106 radiomics features depicting the phenotype of the PCAT surrounding the lesion were calculated. All data were randomly split into a training dataset (75%) and a testing dataset (25%). Then three models (including the conventional model, the PCAT radiomics model, and the combined model) were established in the training dataset using multivariate logistic regression algorithm based on the conventional quantitative features and the PCAT radiomics features after dimension reduction.

RESULTS

A total of 124/306 vessels showed functional ischemia (FFR ≤ 0.80). The radiomics model performed better in discriminating ischemia from non-ischemia than the conventional model in both training (area under the receiver operating characteristic (ROC) curve (AUC): 0.770 vs 0.732, p < 0.05) and testing datasets (AUC: 0.740 vs 0.696, p < 0.05). The combined model showed significantly better discrimination than the conventional model in both training (AUC: 0.810 vs 0.732, p < 0.05) and testing datasets (AUC: 0.809 vs 0.696, p < 0.05).

CONCLUSIONS

The PCAT radiomics model showed good performance in predicting myocardial ischemia. Addition of PCAT radiomics to lesion quantitative characteristics improves the predictive power of functionally relevant CAD.

KEY POINTS

• Based on the plaque characteristics and EAT characteristics, the conventional model showed poor performance in predicting myocardial ischemia. • The PCAT radiomics model showed good prospect in predicting myocardial ischemia. • When combining the radiomics signature with the conventional quantitative features (including plaque features and EAT features), it showed significantly better performance in predicting myocardial ischemia.

Validity and Diagnostic Performance of Computing Fractional Flow Reserve From 2-Dimensional Coronary Angiography Images

BACKGROUND

Measurement of fractional flow reserve (FFR) is the gold standard for determining the physiologic significance of coronary artery stenosis, but newer software programs can calculate the FFR from 2-dimensional angiography images.

METHODS

A retrospective analysis was conducted using the records of patients with intermediate coronary stenoses who had undergone adenosine FFR (aFFR). To calculate the computed FFR, a software program used simulated coronary blood flow using computational geometry constructed using at least 2 patient-specific angiographic images. Two cardiologists reviewed the angiograms and determined the computational FFR independently. Intraobserver variability was measured using κ analysis and the intraclass correlation coefficient. The correlation coefficient and Bland-Altman plots were used to assess the agreement between the calculated FFR and the aFFR.

RESULTS

A total of 146 patients were included, with 95 men and 51 women, with a mean (SD) age of 61.1 (9.5) y. The mean (SD) aFFR was 0.847 (0.072), and 41 patients (27.0%) had an aFFR of 0.80 or less. There was a strong intraobserver correlation between the computational FFRs (r = 0.808; P < .001; κ = 0.806; P < .001). There was also a strong correlation between aFFR and computational FFR (r = 0.820; P < .001) and good agreement on the Bland-Altman plot. The computational FFR had a high sensitivity (95.1%) and specificity (90.1%) for detecting an aFFR of 0.80 or less.

CONCLUSION

A novel software program provides a feasible method of calculating FFR from coronary angiography images without resorting to pharmacologically induced hyperemia.

Computed Tomography-Derived Physiology Assessment: State-of-the-Art Review

Coronary computed tomography angiography (CCTA) and CCTA-derived fractional flow reserve (FFRCT) are the best non-invasive techniques to assess coronary artery disease (CAD) and myocardial ischemia. Advances in these technologies allow a paradigm shift to the use of CCTA and FFRCT for advanced plaque characterization and planning myocardial revascularization.

Decision-Making During Percutaneous Coronary Intervention Guided by Optical Coherence Tomography: Insights From the LightLab Initiative

BACKGROUND

Use of intracoronary imaging is associated with improved outcomes in patients undergoing percutaneous coronary intervention (PCI). Yet, the impact of intracoronary imaging on real-time physician decision-making during PCI is not fully known.

METHODS

The LightLab Initiative is a multicenter, prospective, observational study designed to characterize the use of a standardized optical coherence tomography (OCT) workflow during PCI. Participating physicians performed pre-PCI and post-PCI OCT in accordance with this workflow and operator assessments of lesion characteristics and treatment plan were recorded for each lesion based on angiography alone and following OCT. Physicians were categorized as having low (n=15), intermediate (n=13), or high (n=14) OCT use in the year preceding participation.

RESULTS

Among 925 patients with 1328 lesions undergoing PCI, the prescribed OCT workflow was followed in 773 (84%) of patients with 836 lesions. Operator lesion assessment and decision-making during PCI changed with OCT use in 86% (721/836) of lesions. Pre-PCI OCT use changed operator decision-making in 80% of lesions, including lesion assessment (45%), vessel preparation strategy (27%), stent diameter (37%), and stent length (36%). Post-PCI OCT changed stent optimization decision-making in 31% of lesions. These findings were consistent across strata of physician prior OCT experience.

CONCLUSIONS

A standardized OCT workflow impacted PCI decision-making in 86% of lesions, with a predominant effect on pre-PCI lesion assessment and planning of treatment strategy. This finding was consistent regardless of operator experience level and provides insight into mechanisms by which intravascular imaging might improve PCI outcomes.

ASSOCIATION OF FRACTIONAL FLOW RESERVE WITH CLINICAL AND ANGIOGRAPHIC CHARACTERISTICS OF PATIENTS WITH STABLE CORONARY ARTERY DISEASE

OBJECTIVE

The aim: To identify clinical and angiographic factors, associated with fractional flow reserve (FFR), in stable coronary artery disease (CAD) patients.

PATIENTS AND METHODS

Materials and methods: The study consecutively enrolled 68 patients with stable CAD (mean age (63±8,0) ys) and angiographically intermediate coronary lesions (diameter stenosis 50-90 %), with FFR assessment. Stable angina of CCS classes II and III was diagnosed in 42 (62 %) and 15 (22 %) patients, respectively; left ventricular hypertrophy (LVH) - 27 (40 %); severe coronary stenosis (SCS) (70-90 %) - 46 (68 %). The overall CAD complexity was assessed by SYNTAX score. FFR «negative» group (FFRNEG) included the patients with non-significant FFRs (>0,80) (n=28 [41 %]). In case of at least one significant FFR (≤0,80), a patient was assigned to FFR «positive» group (FFRPOS) (n=40 [59 %]).

RESULTS

Results: FFRPOS (vs. FFRNEG, respectively) was characterized by the higher frequency of angina class III (32 % vs. 7 %; p<0,001), LVH (53 % vs. 21 %; p=0,010) and SCS (98 % vs. 25 %; p<0,001). The SYNTAX score was strongly associated with FFR ≤0,70 and ≤0,65, and moderately - with FFR ≤0,65.

CONCLUSION

Conclusions: In patients with stable CAD and intermediate coronary artery stenosis, the presence of at least one functionally significant lesion (FFR ≤0,80) was associated with the higher prevalence of angina class III, LVH and more advanced coronary stenosis (≥70 %). The greater overall CAD complexity increased the probability for the angiographically significant coronary lesions to be more functionally compromised.

Intravascular ultrasound guidance for lower extremity arterial and venous interventions

This review details the utility of intravascular ultrasound (IVUS) for the management of peripheral artery and venous disease. The purpose of this document is to provide an update in the use of IVUS in peripheral arterial and venous pathology and demonstrate the use of IVUS as a practical diagnostic imaging procedure to evaluate and treat peripheral vascular disorders. IVUS, a diagnostic tool that relies on sound waves to produce precise images of the vessel being evaluated, was originally introduced to the medical community for the purposes of peripheral artery imaging, though it was quickly adapted for coronary interventions with positive outcomes. The utility of IVUS includes vessel measurement, pre- and post-procedural planning, treatment optimisation, and detection of thrombus, dissection or calcium severity. While angiography remains the standard imaging approach during peripheral intervention, multiple observational studies and small prospective trials have shown that in comparison, IVUS provides more accurate imaging detail, which may improve procedural outcomes. IVUS can also address limitations of angiography, including the need to administer contrast medium and eliminate the ambiguity associated with other forms of imaging. This review provides contemporary examples of where IVUS is being used during peripheral intervention as well as representative imaging to serve as a resource for the practising clinician.

Factors Predicting 150 and 200 Microgram Adenosine Requirement during Four Increasing Doses of Intracoronary Adenosine Bolus Fractional Flow Reserve Assessment

Direct intracoronary adenosine bolus is an excellent alternative to intravenous adenosine fractional flow reserve (FFR) measurement. This study, during four increasing adenosine boluses (50, 100, 150, and 200 mcg), aimed to explore clinical and angiographic predictors of coronary stenotic lesions for which the significant ischemic FFR (FFR ≤ 0.8) occurred at 150 and 200 mcg adenosine doses. Data from 1055 coronary lesions that underwent FFR measurement at the Central Chest Institute of Thailand from August 2011 to July 2021 were included. Baseline clinical and angiographic characteristics were analyzed. The FFR ≤ 0.8 occurred at adenosine 150 and 200 mcg boluses in 47 coronary lesions, while the FFR ≤ 0.8 occurred at adenosine 50 and 100 mcg boluses in 186 coronary lesions. After univariable and multivariable logistic regression analyses, four characteristics, including male sex, younger age, non-smoking status, and FFR procedure of RCA, were predictors of the occurrence of FFR ≤ 0.8 at adenosine 150 and 200 mcg doses. Combining all four predictors as a predictive model resulted in an AuROC of 0.72 (95% CI: 0.68–0.76), an 86% negative predictive value. Comparing these four predictors, the FFR procedure of RCA gave the most predictive power, with the AuROC of 0.60 (95% CI: 0.56–0.63).

Percutaneous Coronary Angioplasty in Patients with Cancer: Clinical Challenges and Management Strategies

The number of cancer survivors in the United States is projected to increase by 31% by 2030. With advances in early screening, diagnosis and therapeutic strategies, a steadily increasing number of patients are surviving cancer. Coronary artery disease (CAD) is now one of the leading causes of death amongst cancer survivors, with the latter group of patients having a higher risk of CAD compared to the general population. Our review covers a range of specific challenges faced by doctors when considering percutaneous coronary interventions (PCI) in cancer patients; clinical outcomes in cancer patients undergoing PCI, as well as some important technical considerations to be made when making decisions regarding the management strategy in this special population of patients.

The association between provider characteristics and post-catheterization interventions

Objectives

To examine whether the demographics of providers’ prior year patient cohorts, providers’ historic degree of catheter-based fractional flow reserve (FFR) utilization, and other provider characteristics were associated with post-catheterization performance of percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG).

Study design

A retrospective, observational analysis of outpatient claims data was performed.

Methods

All 2018 outpatient catheterization claims from a national organization offering commercial and Medicare Advantage health plans were examined. Claims were excluded if the patient had a prior catheterization in 2018, had any indications of CABG or valvular heart disease in the prior year of claims, or if the provider had ≤10 catheterization claims in 2017. Downstream PCI and CABG were determined by examining claims 0–30 days post-catheterization. Using multivariate mixed effects logistic regression with provider identity random effects, the association between post-catheterization procedures and provider characteristics was assessed, controlling for patient characteristics.

Results

The sample consisted of 31,920 catheterization claims pertaining to procedures performed by 964 providers. Among the catheterization claims, 8,554 (26.8%) were followed by PCI and 1,779 (5.6%) were followed by CABG. Catheterizations performed by providers with older prior year patient cohorts were associated with higher adjusted odds of PCI (1.78; CI: 1.26–2.53), even after controlling for patient age. Catheterizations performed by providers with greater historic use of FFR had significantly higher adjusted odds of being followed by PCI (1.73; CI: 1.26–2.37).

Conclusion

Provider characteristics may impact whether patients receive a procedure post-catheterization. Further research is needed to characterize this relationship.

Diagnostic performance of intravascular ultrasound-based fractional flow reserve versus angiography-based quantitative flow ratio measurements for evaluating left main coronary artery stenosis

OBJECTIVES

We compared the diagnostic performance of the ultrasonic flow ratio (UFR) and quantitative flow ratio (QFR) for left main coronary artery (LMCA) stenosis.

BACKGROUND

Evaluation of LMCA stenosis remains challenging because of its complex pathogenesis and severity. Computing QFR allows rapid determination of fractional flow reserve (FFR) from coronary angiograms. A novel intravascular ultrasound (IVUS)-based FFR (UFR) allows rapid FFR computation from IVUS images. Neither of the computational approaches required a pressure wire or hyperemia induction. Previous studies have validated the good diagnostic accuracy of QFR and UFR in identifying hemodynamically significant coronary stenosis using FFR as the reference standard.

METHODS

This retrospective observational study enrolled consecutive patients with intermediate-grade LMCA stenosis who underwent IVUS evaluation. UFR and QFR of all LMCA stenosis patients were assessed, their correlation and agreement were analyzed, and diagnostic performance of UFR in LMCA stenosis was evaluated.

RESULTS

Eighty-three paired comparisons between UFR and QFR were obtained. UFR excellently correlated with QFR (r = 0.74, p < 0.01). The Bland-Altman plot showed good agreement between UFR and QFR (mean differences: 0.01 ± 0.05, p = 0.34). The area under the curve of UFR for identifying physiological LMCA stenosis was 0.97 (95% confidence interval [CI]: 0.93-1.00, p < 0.01). The overall UFR diagnostic accuracy was 0.95 (95% CI: 0.88-0.99).

CONCLUSIONS

UFR showed excellent correlation and good agreement with QFR in LMCA stenosis assessment, indicating that it is highly feasible to use UFR for functional evaluation of LMCA stenosis.

Fractional Flow Reserve: Patient Selection and Perspectives

The aim of this review was to discuss the current practice and patient selection for invasive FFR, new techniques to estimate invasive FFR and future of coronary physiology tests. We elaborate on the indication and application of FFR and on the contraindications and concerns in certain patient populations.

Diastolic versus systolic coronary computed tomography angiography derived fractional flow reserve for the identification of lesion-specific ischemia

OBJECTIVES

To investigate the measurement discrepancy of coronary computed tomography angiography (CTA)-derived fractional flow reserve (FFR) between diastolic (CT-FFR-D) and systolic (CT-FFR-S) phases using FFR as the reference standard.

METHODS

Participants, suspected of coronary artery disease and indicated for invasive coronary angiography (ICA) and FFR and coronary CTA and CT-FFR, were enrolled in this study (Clinicaltrials.gov:NCT03692936) from September 2018 to October 2019. For every participant, coronary CTA of both systolic and diastolic phases was postprocessed to calculate CT-FFR-S and CT-FFR-D, respectively. Diagnostic sensitivity, specificity, accuracy, and the area under the receiver operating characteristic (ROC) curve were compared.

RESULTS

A total of 181 lesions from 151 participants (mean age 54.5 ± 7.8 years, 113 males) were analyzed. Of these, 129 lesions from 110 participants were successfully measured both in diastolic and systolic phases. Sensitivity, specificity, and accuracy of CT-FFR-D and CT-FFR-S on per-patient level were 88.9%, 91.3%, 90.1% and 66.7%, 87.7%, 76.7%, on per-vessel level were 89.5%, 91.5%, 90.6% and 66.7%, 87.0%, 77.9%, respectively. The ROC curve of CT-FFR-D was significantly higher than that of CT-FFR-S on both per-patient and per-vessel levels (0.938 vs. 0.771, 0.935 vs. 0.772, both p < 0.0001). In severe hemodynamic lesions (FFR ≤ 0.7), the absolute difference between CT-FFR-S and FFR was significantly higher than that between CT-FFR-D and FFR [0.1636, inter-quartile range (IQR): 0.0662-0.2586 vs. 0.0953, IQR: 0.0496-0.1702, p = 0.035].

CONCLUSION

CT-FFR derived in diastole was superior to that derived in systole in detecting coronary ischemic lesions. For lesions with FFR < 0.7, CT-FFR measured in the diastolic phase was noted to be more closely approximated to FFR.

Image-based computational fluid dynamics for estimating pressure drop and fractional flow reserve across iliac artery stenosis: A comparison with in-vivo measurements

Computational Fluid Dynamics (CFD) and time-resolved phase-contrast magnetic resonance imaging (PC-MRI) are potential non-invasive methods for the assessment of the severity of arterial stenoses. Fractional flow reserve (FFR) is the current "gold standard" for determining stenosis severity in the coronary arteries but is an invasive method requiring insertion of a pressure wire. CFD derived FFR (vFFR) is an alternative to traditional catheter derived FFR now available commercially for coronary artery assessment, however, it can potentially be applied to a wider range of vulnerable vessels such as the iliac arteries. In this study CFD simulations are used to assess the ability of vFFR in predicting the stenosis severity in a patient with a stenosis of 77% area reduction (>50% diameter reduction) in the right iliac artery. Variations of vFFR, overall pressure drop and flow split between the vessels were observed by using different boundary conditions. Correlations between boundary condition parameters and resulting flow variables are presented. The study concludes that vFFR has good potential to characterise iliac artery stenotic disease.

Intravascular Imaging Guidance Reduce 1-Year MACE in Patients Undergoing Rotablator Atherectomy-Assisted Drug-Eluting Stent Implantation

Objectives: This study aimed to investigate the incidence of 1-year major adverse cardiac events (MACE) compared between intravascular imaging guidance and angiographic guidance in patients undergoing rotablator atherectomy (RA)-assisted percutaneous coronary intervention (PCI) with drug-eluting stent (DES) implantation.

Methods: This retrospective analysis included 265 consecutive patients with heavy calcified lesion who underwent RA-assisted PCI with DES implantation at our institution during the January 2016-December 2018 study period. This study was approved by the Siriraj Institutional Review Board. Patients were divided into either the angiographic guidance PCI group or the imaging guidance PCI group, which was defined as intravascular ultrasound or optical coherence tomography. The primary endpoint was 1-year MACE.

Results: Two hundred and sixty-five patients were enrolled, including 188 patients in the intravascular imaging guidance group, and 77 patients in the angiographic guidance group. One-year MACE was significantly lower in the imaging guidance group compared to the angiographic guidance group (4.3 vs. 28.9%, respectively; odds ratio (OR): 9.06, 95% CI: 3.82–21.52; p < 0.001). The 1-year rates of all-cause death (OR: 8.19, 95% CI: 2.15–31.18; p = 0.002), myocardial infarction (MI) (OR: 6.13, 95% CI: 2.05–18.3; p = 0.001), and target vessel revascularization (TVR) (OR: 3.67, 95% CI: 1.13–11.96; p = 0.031) were also significantly lower in the imaging guidance group compared with the angiographic guidance group. The rate of stroke was non-significantly different between groups.

Conclusion: In patients with heavy calcified lesion undergoing RA-assisted DES implantation, the intravascular imaging guidance significantly reduced the incidence of 1-year MACE, all-cause death, MI, and TVR compared to the angiographic guidance.

Coronary CT Fractional Flow Reserve before Transcatheter Aortic Valve Replacement: Clinical Outcomes

Background The role of CT angiography-derived fractional flow reserve (CT-FFR) in pre-transcatheter aortic valve replacement (TAVR) assessment is uncertain. Purpose To evaluate the predictive value of on-site machine learning-based CT-FFR for adverse clinical outcomes in candidates for TAVR. Materials and Methods This observational retrospective study included patients with severe aortic stenosis referred to TAVR after coronary CT angiography (CCTA) between September 2014 and December 2019. Clinical end points comprised major adverse cardiac events (MACE) (nonfatal myocardial infarction, unstable angina, cardiac death, or heart failure admission) and all-cause mortality. CT-FFR was obtained semiautomatically using an on-site machine learning algorithm. The ability of CT-FFR (abnormal if ≤0.75) to predict outcomes and improve the predictive value of the current noninvasive work-up was assessed. Survival analysis was performed, and the C-index was used to assess the performance of each predictive model. To compare nested models, the likelihood ratio χ² test was performed. Results A total of 196 patients (mean age ± standard deviation, 75 years ± 11; 110 women [56%]) were included; the median time of follow-up was 18 months. MACE occurred in 16% (31 of 196 patients) and all-cause mortality in 19% (38 of 196 patients). Univariable analysis revealed CT-FFR was predictive of MACE (hazard ratio [HR], 4.1; 95% CI: 1.6, 10.8; P = .01) but not all-cause mortality (HR, 1.2; 95% CI: 0.6, 2.2; P = .63). CT-FFR was independently associated with MACE (HR, 4.0; 95% CI: 1.5, 10.5; P = .01) when adjusting for potential confounders. Adding CT-FFR as a predictor to models that include CCTA and clinical data improved their predictive value for MACE (P = .002) but not all-cause mortality (P = .67), and it showed good discriminative ability for MACE (C-index, 0.71). Conclusion CT angiography-derived fractional flow reserve was associated with major adverse cardiac events in candidates for transcatheter aortic valve replacement and improved the predictive value of coronary CT angiography assessment. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Choe in this issue.

Invasive coronary physiology assessment for patients with stable coronary disease

Visual assessment of coronary stenosis severity using conventional coronary angiography is associated with wide inter-operator variability and a weak relationship with hemodynamics. Invasive coronary physiology assessment using fractional flow reserve (FFR) has been shown to be safe and beneficial. Large multicenter randomized trials have demonstrated the superiority of FFR-guided percutaneous coronary intervention (PCI) in reducing the risk of major cardiac adverse events, number of stents used, and total cost in patients with multi-vessel coronary disease. FFR requires vasodilatory agents for the microvasculature to induce maximal hyperemia, which carry a slight risk, cost, and effort. Non-hyperemic pressure ratios (NHPR) provide a physiologic metric without vasodilator medications but with more limited clinical outcomes data. The transition from anatomy to physiology for CAD decision-making represents a cultural sea change in the cardiac catheterization laboratory that requires time and retooling.

From anatomy to function and then back to anatomy: invasive assessment of myocardial ischemia in the catheterization laboratory based on anatomy-derived indices of coronary physiology

For many decades, the severity of coronary artery disease (CAD) and the indication to proceed with either percutaneous coronary intervention (PCI) or surgical revascularization has been based on anatomically derived parameters of vessel stenosis, and typically on the percentage of lumen diameter stenosis (DS%) as determined by invasive coronary angiography (CA). However, it is currently a well-accepted concept that pre-specified thresholds of DS% have a weak correlation with the ischemic and functional potential of an epicardial coronary stenosis. In this regard, the introduction of fractional-flow reserve (FFR) has represented a paradigm-shift in the understanding, diagnosis, and treatment of CAD, but the adoption of FFR into the clinical practice remains surprisingly limited and sub-standard, probably because of the inherent drawbacks of pressure-wire-based technology such as additional costs, prolonged procedural time, invasive instrumentation of the target vessel, and use of vaso-dilatory agents causing side effects for patients. For this reason, new modalities are under development or validation to derive FFR from computational fluid dynamics (CFD) applied to a three-dimensional model (3D) of the target vessel obtained from CA, intravascular imaging, or coronary computed tomography angiography. The purpose of this review was to describe the technical details of these anatomy-derived indices of coronary physiology with a special focus on summarizing their workflow, available evidence, and future perspectives about their application in the clinical practice.

Effect of Elevated Left Ventricular End Diastolic Pressure on Instantaneous Wave-Free Ratio and Fractional Flow Reserve Discordance

Background

Instantaneous wave-free ratio (iFR)-guided physiological assessment has been shown to be non-inferior to fractional flow reserve (FFR)-guided assessment for deciding best treatment strategy for angiographically intermediate stenosis. The diagnostic accuracy of iFR compared to FFR reported in various studies is around 80%. Many factors can lead to iFR/FFR discordance, though underlying physiological mechanism of discordance and its associated factors have not been fully evaluated. The effect of left ventricle end diastolic pressure (LVEDP) on iFR/FFR discordance is unknown and needs further evaluation.

Methods

We performed a single center, non-randomized, both retrospective and prospective study. A total of 65 patients with intermediate coronary stenosis undergoing physiological assessment were included in the study. Patients were assigned to two groups (normal LVEDP and high LVEDP group) based on LVEDP cutoff of 15 mm Hg. iFR and FFR were measured for each patient and iFR/FFR results were compared between the two groups.

Results

A significantly large number of patients in elevated LVEDP group had iFR/FFR discordance compared to normal LVEDP group (42.8% vs. 6.7%, P = 0.001). More patients with acute coronary syndrome (ACS) had discordance compared to stale coronary artery disease (CAD) patients (53% vs. 15%, P = 0.003).

Conclusions

Elevated LVEDP can affect iFR and FFR measurements and can lead to discordance. Further studies are required to determine effect of elevated LVEDP on iFR/FFR discordance and whether such discordance is clinically relevant. “Normal range” iFR results should be cautiously interpreted in patients with elevated LVEDP, especially those with ACS.

Optical coherence tomography-guided coronary stent implantation compared to angiography: a multicentre randomised trial in PCI - design and rationale of ILUMIEN IV: OPTIMAL PCI

AIMS

Randomised trials have demonstrated improvement in clinical outcomes with intravascular ultrasound (IVUS)-guided percutaneous coronary intervention (PCI) compared with angiography-guided PCI. The ILUMIEN III trial demonstrated non-inferiority of an optical coherence tomography (OCT)- versus IVUS-guided PCI strategy in achieving similar post-PCI lumen dimensions. ILUMIEN IV is a large-scale, multicentre, randomised trial designed to demonstrate the superiority of OCT- versus angiography-guided stent implantation in patients with high-risk clinical characteristics (diabetes) and/or complex angiographic lesions in achieving larger post-PCI lumen dimensions and improving clinical outcomes.

METHODS AND RESULTS

ILUMIEN IV is a prospective, single-blind clinical investigation that will randomise between 2,490 and 3,656 patients using an adaptive design to OCT-guided versus angiography-guided coronary stent implantation in a 1:1 ratio. The primary endpoints are: (1) post-PCI minimal stent area assessed by OCT in each randomised arm, and (2) target vessel failure, the composite of cardiac death, target vessel myocardial infarction, or ischaemia-driven target vessel revascularisation. Clinical follow-up will continue for up to two years. The trial is currently enrolling, and the principal results are expected in 2022.

CONCLUSIONS

The large-scale ILUMIEN IV randomised controlled trial will evaluate the effectiveness of OCT-guided versus angiography-guided PCI in improving post-PCI lumen dimensions and clinical outcomes in patients with diabetes and/or with complex coronary lesions.

TRIAL REGISTRATION

NCT03507777.

Case Report: The Role of Intravascular Ultrasonography in Patients Underwent Percutaneous Coronary Intervention

Intravascular ultrasonography (IVUS) has an important role as a complimentary diagnostic tool in percutaneous coronary intervention procedure. IVUS provides valuable information regarding coronary vessel lumen and dimension and also plaque burden and its characteristic. The main use of IVUS in PCI is to guide the choose of interventional strategies to optimize stent deployment. Since drug eluting stent (DES) has promised to decrease the incidence in stent restenosis and stent thrombosis than bare metal stent, but neither the suboptimal results nor the complication after stenting with DES is still high. Thus, optimization of stent deployment under IVUS guidance is important in cases to decrease stent failure after PCI procedure, as well as to decrease complication rate after stenting in order to decrease mortality rate caused by coronary artery disease. We present here the use of IVUS guidance in a 43 and 46 year-old man underwent PCI.

The role of intravascular ultrasound in percutaneous coronary intervention of complex coronary lesions

Intravascular ultrasound (IVUS) is a catheter-based coronary imaging technique. It utilises the emission & subsequent detection of reflected high frequency (30-60 MHz) sound waves to create high resolution, cross-sectional images of the coronary artery. IVUS has been the cornerstone of intracoronary imaging for more than two decades. When compared to the invasive coronary angiogram which studies only the silhouette of the contrast-filled artery lumen, IVUS also crucially images the vessel wall. Because of this capability, IVUS has greatly facilitated understanding of the coronary atherosclerosis process. Such insights from IVUS reveal how commonly and extensively plain angiography underestimates the true extent of coronary plaque, the characteristics of plaques prone to rupture and cause acute coronary syndromes (lipid rich, thin cap atheroma), and a realisation of the widespread occurrence of vessel remodelling in response to atherosclerosis. Similarly, IVUS has historically provided salutary mechanistic insights that have guided many of the incremental advances in the techniques of percutaneous coronary intervention (PCI). Examples include mechanisms of in-stent restenosis, and the importance of high-pressure post-dilatation of stents to ensure adequate stent apposition and thereby reduce the occurrence of stent thrombosis. IVUS also greatly facilitates the choice of correct diameter and length of stent to implant. Overall, a compelling body of evidence indicates that use of intravascular ultrasound in PCI helps to achieve optimal technical results and to mitigate the risk of adverse cardiac events. In this review, the role of intravascular ultrasound as an adjunct to PCI in complex coronary lesions is explored. The complex coronary situations discussed are the left main stem, ostial stenoses, bifurcation stenoses, thrombotic lesions, the chronically occluded coronary artery, and calcified coronary artery disease. By thorough review of the available evidence, we establish that the advantages of IVUS guidance are particularly evident in each of these complex CAD subsets. In particular, some consider the use of IVUS to be almost mandatory in left main PCI. A comparison with other intracoronary imaging techniques is also explored.

Intravascular ultrasound guidance in the evaluation and treatment of left main coronary artery disease

Percutaneous coronary intervention (PCI) of left main coronary artery (LMCA) disease has become an acceptable revascularization strategy. Evaluating the extent and characteristics of obstructive disease of the LMCA by angiography is challenging and limited in its accuracy. In contrast, intravascular ultrasound (IVUS) provides accurate imaging of the coronary lumen as well as quantitative measurements and quantitative assessment of the vessel wall components. IVUS for LMCA PCI should be performed before, during, and after intervention; IVUS enhances every step in the procedure and is associated with a mortality advantage in comparison with angiographic guidance alone. In this review, we provide an update on LMCA PCI and the role of IVUS for lesion assessment and stent optimization. In addition, the latest clinical evidence of the benefits of IVUS-guided LMCA PCI as compared to angiography is reviewed.

Comparison of Stent Expansion Using a Volumetric Versus the Conventional Method Through Optical Coherence Tomography in an All-Comers Population

INTRODUCTION

A volumetric approach to measure stent expansion derived from optical coherence tomography (OCT) is superior in regards to clinical outcomes when compared to the conventional method. The current software already performs a semi-automatic assessment and it is available as a clinical tool, however data is still scarce. We evaluated the stent expansion analysis that uses a volumetric vessel model, called minimum expansion index - MEI and compared to the conventional model, which utilizes the minimum stent area expansion (MSAx) indexed to the references, and its potential impact on procedural decision-making strategy in percutaneous coronary intervention.

METHODS

This was a prospective, all-comers single center study, from all patients undergoing OCT-guided PCI between September 2018 and May 2019. We utilized the APTIVUE™ OPTIS 5.2 software (Abbott, Santa Clara, CA) to evaluate MEI and MSAx measurements after reference adjustments.

RESULTS

We included 100 patients with mean age of 64 ± 12.5 years, 68% were men, and the main arteries analyzed through OCT were LAD (48%), RCA (31%) and LCx (21%). The mean MEI was 77.6% ± 16.7% and the mean MSAx was 71.6% ± 16.9%. MEI location differed from MSAx in 70% of cases, and in those cases the mean distance between MEI and MSAx was 15.3 mm ± 12.4 mm. In 53% of the times, the stent underexpansion based on MEI was located proximally to the MSAx by 18.1 mm ± 11.8 mm. Furthermore, in 42% of the total cases, MEI would change the intervention strategy based on the stent underexpansion being in a different location ≥10 mm in comparison to MSAx (34%) associated with the discrepancy between expansion indexes for MEI and MSAx (22%).

CONCLUSION

We concluded that MEI location did not correlate to the conventional MSAx in two thirds of the cases. Moreover, compared to MEI, the MSAx assessment yielded lower expansion values in different stent positions, potentially changing the appropriate post-stent optimization, which thus would impact the decision-making strategy in almost half of the patients.

Optical Coherence Tomography Facilitating Early Withdrawal of Antiplatelet Agents in a High–Bleeding Risk Patient

Optical coherence tomography (OCT) can guide percutaneous coronary interventions to optimize results, thus minimizing the risk of stent thrombosis. We present the case of a cancer patient, paroxysmal atrial fibrillation, and unstable angina who underwent OCT–guided complex percutaneous coronary intervention and who required early discontinuation of antiplatelet therapy because of major bleeding. (Level of Difficulty: Beginner.)

Comparison between functional and intravascular imaging approaches guiding percutaneous coronary intervention: A network meta-analysis of randomized and propensity matching studies

BACKGROUND

The optimal approach to guide percutaneous coronary intervention (PCI) has yet to be defined. The aim of this study was to compare functional driven (fractional flow reserve) versus intravascular imaging (intravascular ultrasound, IVUS, and/or optical coherence tomography, OCT) versus standard (coronary angiography only, CA)-guided PCI.

METHODS

Randomized controlled trials (RCTs) and propensity score weight-matched studies (PSWMs) comparing FFR versus IVUS versus OCT versus CA-guided PCI were included. Major adverse cardiovascular event (MACE; a composite end point of death or myocardial infarction [MI] or revascularization) was the primary endpoint, whereas definite stent thrombosis (ST) and single components of MACE were the secondary ones. Primary analyses were performed including only RCTs, secondary also with PSWMs.

RESULTS

Thirty-three studies were included in the analysis, 16 RCTs and 17 PSWMs. After 2 (1-3) years, IVUS performed better for MACE than CA (odds ratio [OR] 0.75 0.52-0.88), whereas there was just a trend for FFR (OR 0.81, 0.64-1.02). These results were mainly driven by reduced risk of all cause death, MI (FFR OR 0.74:0.57-0.99 and IVUS OR 0.82:0.54-0.94) and revascularization. IVUS reduced ST while FFR did not, and at meta-regression analysis, there was a trend for superiority of IVUS versus FFR to reduce subsequent MI in acute coronary syndrome (ACS) patients. The present results were consistent also after adding studies with PSWMs.

CONCLUSIONS

Functional and intravascular imaging approaches seem to perform similarly in term of clinical outcomes, while both performed better compared with the standard approach. Imaging showed a potential benefit for ACS patients. The present results stress the need for a wider use of functional or imaging driven PCI.

Invasive fractional flow reserve: Which technology is best?

Invasive pressure measurements using hyperemic fractional flow reserve (FFR) and nonhyperemic pressure measurements (NHPR) are superior to angiography alone for assessment of 50-90% stenoses. FFR devices using piezoelectric and optical sensors achieve 94% concordance in FFR values; microcatheter designs have more lesion-crossing failures and less pressure drift compared with guidewire designs. Despite the similarity in statistical performance among FFR devices, interventional cardiologists may prefer to use NHPR to avoid the need for adenosine-related side effects, variations in vasodilator response, and limited application in patients with certain clinical and anatomic features.

Determining the Significance of Coronary Plaque Lesions: Physiological Stenosis Severity and Plaque Characteristics

The evaluation of coronary lesions has evolved in recent years. Physiologic-guided revascularization (particularly with pressure-derived fractional flow reserve (FFR)) has led to superior outcomes compared to traditional angiographic assessment. A greater importance, therefore, has been placed on the functional significance of an epicardial lesion. Despite the improvements in the limitations of angiography, insights into the relationship between hemodynamic significance and plaque morphology at the lesion level has shown that determining the implications of epicardial lesions is rather complex. Investigators have sought greater understanding by correlating ischemia quantified by FFR with plaque characteristics determined on invasive and non-invasive modalities. We review the background of the use of these diagnostic tools in coronary artery disease and discuss the implications of analyzing physiological stenosis severity and plaque characteristics concurrently.

Contemporary practices using intravascular imaging guidance with IVUS or OCT to optimize percutaneous coronary intervention

Introduction: Angiography is routinely used to perform percutaneous coronary intervention (PCI). However, angiography has many limitations that prevent accurate assessment of coronary lesions. The development and evolution of intravascular imaging have offset the limitations of angiography. Overwhelming evidence supports intravascular imaging guidance to optimize PCI results and studies have shown that it is associated with better outcomes. Intravascular ultrasound (IVUS) and optical coherence tomography (OCT) are the most commonly used modalities and both have far greater spatial resolution compared with angiography. There are advantages and disadvantages to both IVUS and OCT, and the optimal modality will depend on patient factors and indications.Areas covered: This review will summarize clinical evidence and current practices in the use of intravascular imaging in PCI. Literature review from year 2000-2019 was completed via PubMed search using keywords.Expert commentary: Intravascular imaging is an essential tool in PCI that has outcome implications, but it is still underutilized. Proper image acquisition, accurate interpretation, and correct decision-making are needed for patients to benefit from imaging-guided PCI. Training and education are essential in successful utilization of imaging technology. High-definition IVUS is likely to gain favor as there is improved image resolution without the use of contrast.

Lancaster G, W. Zarich S. Invasive Evaluation of the Microvasculature in Acute Myocardial Infarction: Coronary Flow Reserve versus the Index of Microcirculatory Resistance

Acute myocardial infarction (AMI) is one of the most common causes of death in both the developed and developing world. It has high associated morbidity despite prompt institution of recommended therapy. The focus over the last few decades in ST-segment elevation AMI has been on timely reperfusion of the epicardial vessel. However, microvascular consequences after reperfusion, such as microvascular obstruction (MVO), are equally reliable predictors of outcome. The attention on the microcirculation has meant that traditional angiographic/anatomic methods are insufficient. We searched PubMed and the Cochrane database for English-language studies published between January 2000 and November 2019 that investigated the use of invasive physiologic tools in AMI. Based on these results, we provide a comprehensive review regarding the role for the invasive evaluation of the microcirculation in AMI, with specific emphasis on coronary flow reserve (CFR) and the index of microcirculatory resistance (IMR).

Computational instantaneous wave-free ratio (IFR) for patient-specific coronary artery stenoses using 1D network models

In this work, we estimate the diagnostic threshold of the instantaneous wave-free ratio (iFR) through the use of a one-dimensional haemodynamic framework. To this end, we first compared the computed fractional flow reserve (cFFR) predicted from a 1D computational framework with invasive clinical measurements. The framework shows excellent promise and utilises minimal patient data from a cohort of 52 patients with a total of 66 stenoses. The diagnostic accuracy of the cFFR model was 75.76%, with a sensitivity of 71.43%, a specificity of 77.78%, a positive predictive value of 60%, and a negative predictive value of 85.37%. The validated model was then used to estimate the diagnostic threshold of iFR. The model determined a quadratic relationship between cFFR and the ciFR. The iFR diagnostic threshold was determined to be 0.8910 from a receiver operating characteristic curve that is in the range of 0.89 to 0.9 that is normally reported in clinical studies.

Optimizing the Technique for Invasive Fractional Flow Reserve to Assess Lesion-Specific Ischemia

Background:

Invasive fractional flow reserve (FFR INV ) is the standard technique for assessing myocardial ischemia. Pressure distortions and measurement location may influence FFR INV interpretation. We report a technique for performing invasive fractional flow reserve (FFR INV ) by minimizing pressure distortions and identifying the proper location to measure FFR INV .

Methods:

FFR INV recordings were obtained prospectively during manual hyperemic pullback in 100 normal and diseased coronary arteries with single stenosis, using 4 measurements from the terminal vessel, distal-to-the-lesion, proximal vessel, and guiding catheter. FFR INV profiles were developed by plotting FFR INV values ( y -axis) and site of measurement ( x -axis), stratified by stenosis severity. FFR INV ≤0.8 was considered positive for lesion-specific ischemia.

Results:

Erroneous FFR INV values were observed in 10% of vessels because of aortic pressure distortion and in 21% because of distal pressure drift; these were corrected by disengagement of the guiding catheter and re-equalization of distal pressure/aortic pressure, respectively. There were significant declines in FFR INV from the proximal to the terminal vessel in normal and stenotic coronary arteries ( P <0.001). The rate of positive FFR INV was 41% when measured from the terminal vessel and 20% when measured distal-to-the-lesion ( P <0.001); 41.5% of positive terminal measurements were reclassified to negative when measured distal-to-the-lesion. Measuring FFR INV 20 to 30 mm distal-to-the-lesion (rather than from the terminal vessel) can reduce errors in measurement and optimize the assessment of lesion-specific ischemia.

Conclusions:

Meticulous technique (disengagement of the guiding catheter, FFR INV pullback) is required to avoid erroneous FFR INV , which occur in 31% of vessels. Even with optimal technique, FFR INV values are influenced by stenosis severity and the site of pressure measurement. FFR INV values from the terminal vessel may overestimate lesion-specific ischemia, leading to unnecessary revascularization.

Non-invasive coronary CT angiography-derived fractional flow reserve: A benchmark study comparing the diagnostic performance of four different computational methodologies

Non-invasive coronary computed tomography (CT) angiography-derived fractional flow reserve (cFFR) is an emergent approach to determine the functional relevance of obstructive coronary lesions. Its feasibility and diagnostic performance has been reported in several studies. It is unclear if differences in sensitivity and specificity between these studies are due to study design, population, or "computational methodology." We evaluate the diagnostic performance of four different computational workflows for the prediction of cFFR using a limited data set of 10 patients, three based on reduced-order modelling and one based on a 3D rigid-wall model. The results for three of these methodologies yield similar accuracy of 6.5% to 10.5% mean absolute difference between computed and measured FFR. The main aspects of modelling which affected cFFR estimation were choice of inlet and outlet boundary conditions and estimation of flow distribution in the coronary network. One of the reduced-order models showed the lowest overall deviation from the clinical FFR measurements, indicating that reduced-order models are capable of a similar level of accuracy to a 3D model. In addition, this reduced-order model did not include a lumped pressure-drop model for a stenosis, which implies that the additional effort of isolating a stenosis and inserting a pressure-drop element in the spatial mesh may not be required for FFR estimation. The present benchmark study is the first of this kind, in which we attempt to homogenize the data required to compute FFR using mathematical models. The clinical data utilised in the cFFR workflows are made publicly available online.

Intracoronary Cavitation as a Cause of Plaque Rupture and Thrombosis Propagation in Patients with Acute Myocardial Infarction: A Computational Study

Background and Objectives

Significant rather than moderate coronary artery stenosis has been postulated to be the main substrate of plaque rupture in acute myocardial infarction (AMI). We evaluate if cavitation could influence the coronary artery plaque rupture contributing to the progression of thrombotic process.

Methods

We reconstructed a 3D model of the left anterior descending coronary artery (LAD) after reviewing the intravascular ultrasound (IVUS) data of 30 consecutive patients with mild to severe coronary artery disease.

Results

Turbulent flow or cavitation occurs in both concentric and eccentric coronary artery stenosis (≥ 75% for the former and ≥ 50% for the latter). The analysis of vapor phase demonstrated that cavitation propagated downstream, creating microbubbles, which exploded when the fluid pressure was lower than the vapor pressure at a local thermodynamic state. The relative higher vorticity magnitude (as turbulent flow in vivo angiogram) observed on the distal cap of the atherosclerotic plaque created a higher turbulence, probably able to destabilize the plaque through a micro-erosion process.

Conclusions

Cavitation seems to be able to promote the thrombotic occlusion within the coronary vessels due the ‘constant injuries’ created by the micro-explosion of bubbles.