Why Is Fractional Flow Reserve After Percutaneous Coronary Intervention Not Always 1.0?

Intravascular Imaging-Based Physiologic Assessment

Intravascular imaging (IVI), including intravascular ultrasound (IVUS) and optical coherence tomography (OCT), is clinically useful for assessing the luminal size, lesion length, and plaque characteristics, as well as for evaluating stent deployment; however, it is not designed to estimate myocardial ischemia accurately. Thus, several types of IVI-derived fractional flow reserve (FFR) (IVI-derived FFR) have been developed and reported. In general, the algorithms of virtual FFR are based on basic fluid dynamics equations (mainly Poiseuille and Borda-Carnot equations) and original microvascular models (fixed velocity or calculating coronary flow reserve). Although the models and assumptions used in the past reports were mostly based on the standard population (not independent patient data), the developed software calculated FFR with high accuracy (88% to 94%) with strong correlations between IVI-derived FFR and wire-based FFR (0.69 to 0.89). Given several other less invasive virtual FFR methods currently available for clinical use, IVI-derived FFR would be limited for the sole use of pre-percutaneous coronary intervention (PCI) physiological evaluation; however, it may play a unique role at PCI guidance and optimization, potentially allowing comprehensive and time/cost-saving assessment of both anatomical and physiological lesion properties using a single diagnostic device.

Prediction of functional results of percutaneous coronary interventions with virtual stenting and quantitative flow ratio

BACKGROUND

The clinical value of residual quantitative flow ratio (rQFR), a novel function of QFR technique, is unknown.

AIM

We investigated the clinical value of rQFR, aimed to predict residual ischemia after virtual percutaneous coronary intervention (vPCI).

METHODS

This is a substudy of the COE-PERSPECTIVE registry, which investigated the prognostic value of post-PCI fractional flow reserve (FFR). From pre-PCI angiograms, QFR and rQFR were analyzed and their diagnostic performance was assessed at blinded fashion using pre-PCI FFR and post-PCI FFR as reference, respectively. The prognostic value of rQFR after vPCI was assessed according to vessel-oriented composite outcome (VOCO) at 2 years.

RESULTS

We analyzed 274 patients (274 vessels) with FFR-based ischemic causing lesions (49%) from 555 screened patients. Pre-PCI QFR and FFR were 0.63 ± 0.10 and 0.66 ± 0.11 (R = 0.756, p < 0.001). rQFR after vPCI and FFR after real PCI were 0.93 ± 0.06 and 0.86 ± 0.07 (R = 0.528, p < 0.001). The mean difference between rQFR and post-PCI FFR was 0.068 (95% limit of agreement: -0.05 to 0.19). Diagnostic performance of rQFR to predict residual ischemia after PCI was good (area under the curve [AUC]: 0.856 [0.804-0.909], p < 0.001). rQFR predicted well the incidence of 2-year VOCO after index PCI (AUC: 0.712 [0.555-0.869], p = 0.041), being similar to that of actual post-PCI FFR (AUC: 0.691 [0.512-0.870], p = 0.061). rQFR ≤0.89 was associated with increased risk of 2-year VOCO (hazard ratio [HR]: 12.9 [2.32-71.3], p = 0.0035). This difference was mainly driven by a higher rate of target vessel revascularization (HR: 16.98 [2.33-123.29], p = 0.0051).

CONCLUSIONS

rQFR estimated from pre-PCI angiography and virtual coronary stenting mildly overestimated functional benefit of PCI. However, it well predicted suboptimal functional result and long-term vessel-related clinical events.

CLINICAL TRIAL REGISTRATION

Influence of fractional flow reserve on the Clinical OutcomEs of PERcutaneouS Coronary Intervention (COE-PESPECTIVE) Registry, NCT01873560.

Physiological assessment after percutaneous coronary intervention: the hard truth

Physiologically guided revascularization, using Fractional Flow Reserve (FFR) or instantaneous wave free ratio (iFR) has been demonstrated to be associated with better long-term outcomes compared to an angiographically-guided strategy, mainly avoiding inappropriate coronary stenting and its associated adverse events. On the contrary, the role of invasive physiological assessment after percutaneous coronary intervention (PCI) is much less well established. However, a large body of evidence suggests that a relevant proportion of patients undergoing PCI with a satisfying angiographic result show instead a suboptimal functional product with a potentially negative prognostic impact. For this reason, many efforts have been focused to identify interventional strategies to physiologically optimize PCI. Measuring the functional result after as PCI, especially when performed after a physiological assessment, implies that the operator is ready to accept the hard truth of an unsatisfactory physiological result despite angiographically optimal and, consequently, to optimize the product with some additional effort. The aim of this review is to bridge this gap in knowledge by better defining the paradigm shift of invasive physiological assessment from a simple tool for deciding whether an epicardial stenosis has to be treated to a thoroughly physiological approach to PCI with the suggestion of a practical flow chart.

Relationship between stent expansion and fractional flow reserve after percutaneous coronary intervention: a post hoc analysis of the DOCTORS trial

BACKGROUND

The best criteria for adequate stent expansion assessment by intracoronary imaging remain debated and their correlation with post-PCI FFR values is unknown.

AIMS

This study aimed to analyse the relationship between stent expansion criteria using optical coherence tomography (OCT) analysis and the final PCI functional result.

METHODS

This post hoc analysis of the DOCTORS study included non-ST-elevation segment ACS patients undergoing OCT-guided PCI. The procedure functional result was assessed by the measurement of fractional flow reserve (FFR). Stent expansion was assessed on OCT runs according to the DOCTORS criteria and ILUMIEN III criteria.

RESULTS

The study included N=116 patients (age: 60.8±11.5 years; male gender: 71%). The final expansion was considered optimal in 10%, acceptable in 9% and unacceptable in 81% of the stents according to ILUMIEN III criteria, although being successful in 70% of the patients according to the DOCTORS criteria. Hypertension and larger proximal reference segment dimension were independent predictors of inadequate device ILUMIEN III expansion. FFR values were, respectively, 0.93 (0.91-0.95) versus 0.95 (0.92-0.97) in patients with optimal+acceptable versus unacceptable ILUMIEN III expansion (p=0.22), 0.94 (0.91-0.97) versus 0.95 (0.93-0.97) in patients with optimal versus non-optimal DOCTORS expansion (p=0.23), and 0.95 (0.92-0.97) versus 0.92 (0.90-0.95) in patients with minimal stent area ≥4.5 mm2 versus <4.5 mm2 (p=0.03).

CONCLUSIONS

In this selected population, no relationship was observed between optimal stent expansion according to ILUMIEN III or DOCTORS OCT criteria and final post-PCI FFR values.

Impact of Poststenting Fractional Flow Reserve on Long-Term Clinical Outcomes: The FFR-SEARCH Study

[Figure: see text].

Association of Improvement in Fractional Flow Reserve With Outcomes, Including Symptomatic Relief, After Percutaneous Coronary Intervention

Importance

Whether the improvement in myocardial perfusion provided by percutaneous coronary intervention (PCI) is associated with symptomatic relief or improved outcomes has not been well investigated.

Objective

To investigate the prognostic value of the improvement in fractional flow reserve (FFR) after PCI (ΔFFR) on patients' symptoms and 2-year outcomes.

Design, Setting, and Participants

This study is a post hoc analysis of data from patients undergoing FFR-guided PCI in the randomized clinical trials Fractional Flow Reserve vs Angiography for Multivessel Evaluation (FAME) 1 (NCT00267774; 2009) and FAME 2 (NCT01132495; 2012), with inclusion of 2 years of follow-up data. The FAME 1 trial included patients with multivessel coronary artery disease from 20 medical centers in Europe and the United States. The FAME 2 trial included patients with stable coronary artery disease involving up to 3 vessels from 28 sites in Europe and North America. Lesions from the group in the FAME 1 trial from whom FFR was measured and the group in the FAME 2 trial who received FFR-guided PCI plus medical therapy were analyzed. Data analysis occurred from May 2017 to May 2018.

Interventions

Measure of post-PCI FFR.

Main Outcomes and Measures

Vessel-oriented clinical events at 2 years, a composite of cardiac death, target vessel-associated myocardial infarction, and target vessel revascularization.

Results

This analysis included 639 patients from whom pre-PCI and post-PCI FFR values were available. Of their 837 lesions, 277 were classified into the lowest tertile (ΔFFR≤0.18), 282 into the middle tertile (0.19≤ΔFFR≤0.31), and 278 into the highest tertile (ΔFFR>0.31). Vessel-oriented clinical events were significantly more frequent in the lowest tertile (n = 25 of 277 [9.1%]) compared with the highest tertile (n = 13 of 278 [4.7%]; hazard ratio, 2.01 [95% CI, 1.03-3.92]; P = .04). In addition, a significant association was observed between ΔFFR and symptomatic relief (odds ratio, 1.33 [95% CI, 1.02-1.74]; P = .02).

Conclusions and Relevance

In this analysis of 2 randomized clinical trials, the larger the improvement in FFR, the larger the symptomatic relief and the lower the event rate. This suggests that measuring FFR before and after PCI provides clinically useful information.

Personalised fractional flow reserve: a novel concept to optimise myocardial revascularisation

AIMS

Fractional flow reserve (FFR) represents the percentage reduction in coronary flow relative to a hypothetically normal artery; however, percutaneous coronary intervention (PCI) seldom achieves physiological normality (FFR 1.00), particularly in the context of diffuse disease. In this study we describe a method for calculating the vessel-specific maximal achievable FFR (FFRmax) providing a personalised assessment of what PCI can achieve.

METHODS AND RESULTS

FFR measurements were obtained from 71 patients (100 arteries) undergoing angiography. Three-dimensional (3D) coronary anatomy was reconstructed from angiographic images. An ideal intervention, in which all stenoses are removed, was modelled, and the FFRmax calculated. The "personalised" FFR (FFRpers) was calculated as measured FFR/FFRmax. PCI was performed in 52 vessels and post-PCI FFR measured in 50. FFRmax was compared to post-PCI measured FFRs. The mean FFRmax was 0.92 (±0.04). This was on average 0.04 (±0.05) higher than the corresponding post-PCI measured FFR (p<0.001). FFRpers was significantly higher (0.06±0.04) than measured FFR (p<0.001), indicating that FFR overestimates flow restoration achievable with PCI.

CONCLUSIONS

A patient's maximal achievable FFR can now be determined prior to PCI. This approach provides a more realistic assessment of the physiological benefit of PCI than is implied by baseline FFR and may prevent unnecessary intervention.

Prospective Randomized Comparison of Fractional Flow Reserve Versus Optical Coherence Tomography to Guide Revascularization of Intermediate Coronary Stenoses: One-Month Results

Background Fractional flow reserve (FFR) and optical coherence tomography (OCT) may help both in assessment and in percutaneous coronary intervention optimization of angiographically intermediate coronary lesions. We designed a prospective trial comparing the clinical and economic outcomes associated with FFR or OCT in angiographically intermediate coronary lesions. Methods and Results Three hundred fifty patients with angiographically intermediate coronary lesions (n=446) were randomized to FFR or OCT guidance. In the FFR arm, percutaneous coronary intervention was performed if FFR was ≤0.80 aiming for a postprocedure FFR >0.90. In the OCT arm, percutaneous coronary intervention was performed if percentage of area stenosis was ≥75% or 50% to 75% with minimal lumen area <2.5 mm2 or plaque ulceration. Costs, angina frequency, and major adverse cardiac events were assessed at 1 month and at 13 months. We present early data at 1 month consistent with a prespecified analysis of secondary end points. Patients randomized to FFR, as compared with OCT, were significantly more commonly managed with medical therapy alone (67.7% versus 41.1%; P<0.001), required less contrast media (245±137 versus 280±129 mL; P=0.004), and exhibited a lower occurrence of contrast-induced acute kidney injury (1.7% versus 8.6%; P=0.034). At 1 month, in comparison to FFR, OCT was associated with increased total costs (2831±1288 versus 4292±3844 euros/patient; P<0.001) whereas occurrence of major adverse cardiac events or significant angina was similar. Conclusions In patients with angiographically intermediate coronary lesions, a functional guidance by FFR, as compared with OCT, increased the rate of patients treated with medical therapy alone. This translated into a significant reduction in administered contrast, contrast-induced acute kidney injury, and total costs at 1 month with FFR. Clinical Trial Registration URL: http://www.clinicaltrialsgov. Unique identifier: NCT01824030.

Fractional flow reserve guided percutaneous coronary intervention optimization directed by high-definition intravascular ultrasound versus standard of care: Rationale and study design of the prospective randomized FFR-REACT trial

BACKGROUND

Post percutaneous coronary intervention (PCI) fractional flow reserve (FFR) is a significant predictor of major adverse cardiac events (MACE). The rationale for low post procedural FFR values often remains elusive based on angiographic findings alone, warranting further assessment using an FFR pullback or additional intravascular imaging. It is currently unknown if additional interventions intended to improve the PCI, decrease MACE rates.

STUDY DESIGN

The FFR REACT trial is a prospective, single-center randomized controlled trial in which 290 patients with a post PCI FFR <0.90 will be randomized (1:1) to either standard of care (no additional intervention) or intravascular ultrasound (IVUS)-directed optimization of the FFR (treatment arm). Eligible patients are those treated with angiographically successful PCI for (un)stable angina or non-ST elevation myocardial infarction (MI). Assuming 45% of patients will have a post PCI FFR <0.90, approximately 640 patients undergoing PCI will need to be enrolled. Patients with a post PCI FFR ≥ 0.90 will be enrolled in a prospective registry. The primary end point is defined as a composite of cardiac death, target vessel MI and clinically driven target vessel revascularisation (target vessel failure) at 1 year. Secondary end points will consist of individual components of the primary end point, procedural success, stent thrombosis and correlations on clinical outcome, changes in post PCI Pd/Pa and FFR and IVUS derived dimensions. All patients will be followed for 3 years.

CONCLUSION

The FFR-REACT trial is designed to explore the potential benefit of HD-IVUS-guided PCI optimization in patients with a post PCI FFR <0.90 (Dutch trial register: NTR6711).