Fractional flow reserve: a review: invasive imaging

Functional assessment of cerebral artery stenosis: A pilot study based on computational fluid dynamics

The fractional pressure ratio is introduced to quantitatively assess the hemodynamic significance of severe intracranial stenosis. A computational fluid dynamics-based method is proposed to non-invasively compute the FPR_CFD and compared against fractional pressure ratio measured by an invasive technique. Eleven patients with severe intracranial stenosis considered for endovascular intervention were recruited and an invasive procedure was performed to measure the distal and the aortic pressure ( P_d and P_a). The fractional pressure ratio was calculated as [Formula: see text]. The computed tomography angiography was used to reconstruct three-dimensional (3D) arteries for each patient. Cerebral hemodynamics was then computed for the arteries using a mathematical model governed by Navier-Stokes equations and with the outflow conditions imposed by a model of distal resistance and compliance. The non-invasive [Formula: see text], [Formula: see text], and FPR_CFD were then obtained from the computational fluid dynamics calculation using a 16-core parallel computer. The invasive and non-invasive parameters were tested by statistical analysis. For this group of patients, the computational fluid dynamics method achieved comparable results with the invasive measurements. The fractional pressure ratio and FPR_CFD are very close and highly correlated, but not linearly proportional, with the percentage of stenosis. The proposed computational fluid dynamics method can potentially be useful in assessing the functional alteration of cerebral stenosis.

Fractional flow reserve and minimum Pd/Pa ratio during intravenous adenosine infusion: very similar but not always the same

AIMS

Maximum and stable hyperaemia are critical prerequisites for the accurate measurement of fractional flow reserve (FFR). However, in some patients in whom hyperaemia is induced through a central vein (IV) the minimum distal coronary pressure to aortic pressure ratio (Pd/Pa ratio) develops before the stabilisation of hyperaemia. We sought to describe the prevalence, magnitude and clinical implications of this phenomenon.

METHODS AND RESULTS

The FFR tracing archive of a single institution was reviewed and a total of 104 high-quality IV-FFR recordings from 90 patients were identified. Whenever the minimum Pd/Pa ratio was found before the onset of stable hyperaemia, a search for the lowest Pd/Pa ratio within the steady-state hyperaemic plateau was performed and labelled as FFRstable. Whilst in most cases the minimum Pd/Pa ratio developed during stable hyperaemia, in 19 cases (prevalence of 18.3% [95% CI: 12.0% to 26.8%]) this value was found before the stabilisation of the hyperaemic state. In such cases, the minimum Pd/Pa ratio stabilised later at a higher level (0.77±0.09 vs. 0.81±0.08, p<0.001) (mean difference, 0.03±0.02, range, 0.01 to 0.10). In terms of dichotomous classification of stenosis severity and if FFRstable had been used to decide on revascularisation, reclassification would have occurred in three (2.9%) cases, all presenting a minimum Pd/Pa ratio ≤0.80 with FFRstable >0.80.

CONCLUSIONS

During IV adenosine infusion, the minimum Pd/Pa ratio occurs before the stabilisation of hyperaemia in a significant proportion of cases. While the overall difference between the minimum Pd/Pa ratio and its FFRstable counterpart is small, reclassification of stenosis severity might occur, if choosing between the minimum and stable values of FFR within the same trace.

Comparative Study between Perfusion Changes and Positive Findings on Coronary Flow Reserve

BACKGROUND

Functional assessment of coronary artery obstruction is used in cardiology practice to correlate anatomic obstructions with flow decrease. Among such assessments, the study of the coronary fractional flow reserve (FFR) has become the most widely used.

OBJECTIVE

To evaluate the correlation between FFR and findings of ischemia obtained by noninvasive methods including stress echocardiography and nuclear medicine and the presence of critical coronary artery obstruction.

METHODS

Retrospective study of cases treated with systematized and standardized procedures for coronary disease between March 2011 and August 2014. We included 96 patients with 107 critical coronary obstructions (> 50% in the coronary trunk and/or ≥ 70% in other segments) estimated by quantitative coronary angiography (QCA) and intracoronary ultrasound (ICUS). All cases presented ischemia in one of the noninvasive studies.

RESULTS

All 96 patients presented ischemia (100%) in one of the functional tests. On FFR study with adenosine 140 g/kg/min, 52% of the cases had values ≤ 0.80. On correlation analysis for FFR ≤ 0.80, the evaluation of sensitivity, specificity, positive and negative predictive values, accuracy, and ROC curve in relation to the stenosis degree and length, and presence of ischemia, no significant values or strong correlation were observed.

CONCLUSION

Coronary FFR using a cut-off value of 0.80 showed no correlation with noninvasive ischemia tests in patients with severe coronary artery obstructions on QCA and ICUS.

Clinical Outcomes of patients with coronary artery disease who underwent FFR evaluation of intermediate coronary lesionS- COFFRS study

Background

We undertook this study to validate the impact of FFR-guided coronary interventions among Indian patients, which is not readily available as of date. Our patients differ from their western counterparts, both in terms of risk profile (younger, more metabolic syndrome, lipid rich diet) as well as their coronary size.

Methods

We retrospectively evaluated 282 patients with intermediate stenosis in their coronary arteries, who underwent FFR to assess the functional severity of the lesion. There were 3 groups: Group 1–FFR > 0.8 and kept on medical follow-up; Group 2–FFR ≤ 0.8 and underwent revascularisation; and Group 3–FFR ≤ 0.8 and refused to undergo revascularization. 281(99.6%) patients had regular follow-up in our clinic.

Results

Median age-57 years (range = 28–78). Males = 230, 90 patients were in Group 1, 175 in group 2 (PCI in 144 & CABG in 31) and 17 in group 3. Median follow-up of patients was 17.9 months (2 to 56 months). Three patients(3.4%) in Group 1 had MACE (1 STEMI, 2 UA); 4 patients (2.3%) in Group 2 had Non-STE-ACS; 7 patients (41%) in Group 3 had MACE (3 deaths with acute LVF, 2 NSTEMI, 2 STEMI)

Conclusion

In our experience, MACE events were not higher in patients with FFR > 0.8 and kept under medical therapy and were similarly lower in patients with FFR ≤0.8 and underwent revascularisation (p = 0.73). Also MACE events were higher in patients with FFR ≤ 0.8 and did not undergo revascularisation compared to other two appropriately treated groups (p = 0.03). FFR based revascularization decision appears to be a safe strategy in Indian patients.

Cardiac CT Imaging of Plaque Vulnerability: Hype or Hope?

Advances in cardiovascular computed tomography (CT) have resulted in an excellent ability to exclude coronary heart disease (CHD). Anatomical information, functional information, and spectral information can already be obtained with current CT technologies. Moreover, novel developments such as targeted nanoparticle contrast agents, photon-counting CT, and phase contrast CT will further enhance the diagnostic value of cardiovascular CT. This review provides an overview of current state of the art and future cardiovascular CT imaging.

Efficacy of intravenous nicorandil for fractional flow reserve assessment: study protocol for a crossover randomised trial

INTRODUCTION

Nicorandil has vasodilatory effects on both the epicardial coronary arteries and the coronary microvasculature, thereby increasing coronary blood flow. Intravenous administration of nicorandil can be applicable for fractional flow reserve (FFR) measurement as a hyperaemic agent and a possible alternative to adenosine. However, the effectiveness of intravenous nicorandil infusion for FFR measurement is largely unclear.

METHODS AND ANALYSIS

This crossover randomised study is being performed to investigate the efficacy of intravenous administration of nicorandil for FFR measurement. Patients with an intermediate coronary artery stenosis who satisfy the eligibility criteria undergo FFR measurement with a consecutive randomised order of patient-blind infusions of continuous intravenous administration of adenosine and a single bolus intravenous administration of nicorandil. The primary end point of the study is the agreement between the FFR values obtained by the intravenous nicorandil and those obtained by the intravenous adenosine. Recruitment of this trial started in November 2015 and will end in March 2017, or until a total of 50 participants have been recruited.

ETHICS AND DISSEMINATION

The protocol was approved by the Institutional Review Board at Chiba University Hospital. Study findings will be published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

UMIN000019309; Pre-results.

Comparison of fractional flow reserve measurements using intracoronary adenosine versus intracoronary sodium nitroprusside infusions in moderately stenotic coronary artery lesions

INTRODUCTION

The aim of this study was to investigate the efficacy and safety of intracoronary (IC) sodium nitroprusside infusion in comparison to IC adenosine for fractional flow reserve (FFR) measurement in moderately diseased coronary artery lesions for functional assessment.

METHODS

During a nine month period, a consecutive of 98 patients with suspected or known coronary artery disease with moderate stenosis found during angiography (40% to 70% stenosis), were enrolled in this study. Hyperemia was induced by bolus doses of IC adenosine followed by sodium nitroprusside for FFR measurement.

RESULTS

Both IC adenosine and IC sodium nitroprusside induced similar and significant reduction in FFR. There was no statistically difference in FFR values between adenosine vs sodium nitroprusside infusions (mean FFR 84.3±6.3 vs 85.7±6.2, p=0.1) respectively. Furthermore, comparing different FFR cut-off points between the groups (FFR<0.75, 0.75-0.8 and >0.8) showed no significant differences (p value=0.7).

CONCLUSION

An IC bolus of sodium nitroprusside (0.6μg/kg) infusion induces a similar degree of hyperemia to IC bolus of 100-300μg of adenosine. Therefore, IC sodium nitroprusside could be considered as an alternative drug to adenosine for FFR measurement with lower side effect profile.

Relation between fractional flow reserve value of coronary lesions with deferred revascularization and cardiovascular outcomes in non-diabetic and diabetic patients

BACKGROUND

FFR of deferred PCI lesions can predict future cardiovascular events. However, the prognostic utility of FFR remains unclear in diabetic patients in view of the potential impact of the diffuse nature of vascular disease process. We aimed to study the relation between fractional flow reserve (FFR) values and long-term outcomes of diabetic and non-diabetic patients with deferred percutaneous coronary intervention (PCI).

METHODS

Patients with FFR assessment and deferred PCI (n=630) were enrolled and stratified according to diabetes mellitus (DM) status and FFR values. Patients were followed over a median of 39months. Cox proportional hazard regression models were used to analyze the association between clinical endpoints and clinical factors such as DM and FFR.

RESULTS

In non-diabetics (n=450), higher FFR values were associated with less cardiovascular events (hazard ratio (HR) for death and myocardial infarction (MI) [95% confidence interval (CI)], 0.61[0.44 to 0.86] per 0.1 increase in FFR, p=0.007; HR for revascularization [95%CI], 0.66[0.49 to 0.9] per 0.1 increase in FFR, p=0.006). In diabetics (n=180), there was no difference in death and MI across the range of FFR values. Among those patients with an FFR >0.85, diabetics had a more than two-fold higher risk of death and MI than non-diabetics (HR [95% CI], 2.20 [1.19 to 4.01], p=0.015).

CONCLUSION

Among non-diabetic patients with deferred PCI, a higher FFR was associated with lower rates of death, MI and revascularization. On the contrary in diabetic patients with deferred revascularization, FFR was not able to differentiate the risk of cardiovascular events.

Diminished Signal Intensities Distal to Intracranial Arterial Stenosis on Time-of-Flight MR Angiography Might Indicate Delayed Cerebral Perfusion

BACKGROUND

Intracranial arterial stenosis (ICAS) is a predominant cause of ischemic stroke in Asia. Changes in the signal intensities (SIs) across ICAS lesions on time-of-flight magnetic resonance angiography (TOF-MRA) have been indicated to partially reflect the hemodynamic significance of the lesions, which we aimed to verify by correlating it with cerebral perfusion features provided by CT perfusion (CTP) imaging.

METHODS

Ischemic stroke or transient ischemic attack patients with unilateral symptomatic stenosis (≥50%) of intracranial internal carotid artery or middle cerebral artery (MCA) were included in this study. Change of SIs across an ICAS lesion on TOF-MRA was calculated by the distal and proximal SI ratio (SIR). Cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) within the MCA territory of ipsilateral and contralateral hemispheres were evaluated on the CTP images at the basal ganglia level. Relative CBV, CBF and MTT were defined as ratios of the values obtained from ipsilateral and contralateral hemispheres. The relationships between SIR and CTP parameters were analyzed.

RESULTS

Fifty subjects (74% male, mean age 62) were recruited. Overall, the mean SIR was 0.77 ± 0.17. SIR of ICAS was significantly, linearly and negatively correlated with ipsilateral CBV (r = -0.335, p = 0.017), ipsilateral MTT (r = -0.301, p = 0.034), and ipsilateral/contralateral MTT ratio (r = -0.443, p = 0.001).

CONCLUSIONS

Diminished SIs distal to ICAS on TOF-MRA might be associated with delayed ipsilateral cerebral perfusion. Changes of the SIs across ICAS lesions on TOF-MRA may be a simple marker to reflect cerebral perfusion changes in patients with symptomatic ICAS.

Calibration Free Beam Hardening Correction for Cardiac CT Perfusion Imaging

Myocardial perfusion imaging using CT (MPI-CT) and coronary CTA have the potential to make CT an ideal noninvasive gate-keeper for invasive coronary angiography. However, beam hardening artifacts (BHA) prevent accurate blood flow calculation in MPI-CT. BH Correction (BHC) methods require either energy-sensitive CT, not widely available, or typically a calibration-based method. We developed a calibration-free, automatic BHC (ABHC) method suitable for MPI-CT. The algorithm works with any BHC method and iteratively determines model parameters using proposed BHA-specific cost function. In this work, we use the polynomial BHC extended to three materials. The image is segmented into soft tissue, bone, and iodine images, based on mean HU and temporal enhancement. Forward projections of bone and iodine images are obtained, and in each iteration polynomial correction is applied. Corrections are then back projected and combined to obtain the current iteration's BHC image. This process is iterated until cost is minimized. We evaluate the algorithm on simulated and physical phantom images and on preclinical MPI-CT data. The scans were obtained on a prototype spectral detector CT (SDCT) scanner (Philips Healthcare). Mono-energetic reconstructed images were used as the reference. In the simulated phantom, BH streak artifacts were reduced from 12±2HU to 1±1HU and cupping was reduced by 81%. Similarly, in physical phantom, BH streak artifacts were reduced from 48±6HU to 1±5HU and cupping was reduced by 86%. In preclinical MPI-CT images, BHA was reduced from 28±6 HU to less than 4±4HU at peak enhancement. Results suggest that the algorithm can be used to reduce BHA in conventional CT and improve MPI-CT accuracy.

Quantitative myocardial perfusion imaging in a porcine ischemia model using a prototype spectral detector CT system

We optimized and evaluated dynamic myocardial CT perfusion (CTP) imaging on a prototype spectral detector CT (SDCT) scanner. Simultaneous acquisition of energy sensitive projections on the SDCT system enabled projection-based material decomposition, which typically performs better than image-based decomposition required by some other system designs. In addition to virtual monoenergetic, or keV images, the SDCT provided conventional (kVp) images, allowing us to compare and contrast results. Physical phantom measurements demonstrated linearity of keV images, a requirement for quantitative perfusion. Comparisons of kVp to keV images demonstrated very significant reductions in tell-tale beam hardening (BH) artifacts in both phantom and pig images. In phantom images, consideration of iodine contrast to noise ratio and small residual BH artifacts suggested optimum processing at 70 keV. The processing pipeline for dynamic CTP measurements included 4D image registration, spatio-temporal noise filtering, and model-independent singular value decomposition deconvolution, automatically regularized using the L-curve criterion. In normal pig CTP, 70 keV perfusion estimates were homogeneous throughout the myocardium. At 120 kVp, flow was reduced by more than 20% on the BH-hypo-enhanced myocardium, a range that might falsely indicate actionable ischemia, considering the 0.8 threshold for actionable FFR. With partial occlusion of the left anterior descending (LAD) artery (FFR < 0.8), perfusion defects at 70 keV were correctly identified in the LAD territory. At 120 kVp, BH affected the size and flow in the ischemic area; e.g. with FFR ≈ 0.65, the anterior-to-lateral flow ratio was 0.29 ± 0.01, over-estimating stenosis severity as compared to 0.42 ± 0.01 (p < 0.05) at 70 keV. On the non-ischemic inferior wall (not a LAD territory), the flow ratio was 0.50 ± 0.04 falsely indicating an actionable ischemic condition in a healthy territory. This ratio was 1.00 ± 0.08 at 70 keV. Results suggest that projection-based keV imaging with the SDCT system and proper processing could enable useful myocardial CTP, much improved over conventional CT.

Clinical Relevance of Coronary Fractional Flow Reserve: Art-of-state

Objective:

The objective was to delineate the current knowledge of fractional flow reserve (FFR) in terms of definition, features, clinical applications, and pitfalls of measurement of FFR.

Data Sources:

We searched database for primary studies published in English. The database of National Library of Medicine (NLM), MEDLINE, and PubMed up to July 2014 was used to conduct a search using the keyword term “FFR”.

Study Selection:

The articles about the definition, features, clinical application, and pitfalls of measurement of FFR were identified, retrieved, and reviewed.

Results:

Coronary pressure-derived FFR rapidly assesses the hemodynamic significance of individual coronary artery lesions and can readily be performed in the catheterization laboratory. The use of FFR has been shown to effectively guide coronary revascularization procedures leading to improved patient outcomes.

Conclusions:

FFR is a valuable tool to determine the functional significance of coronary stenosis. It combines physiological and anatomical information, and can be followed immediately by percutaneous coronary intervention (PCI) if necessary. The technique of FFR measurement can be performed easily, rapidly, and safely in the catheterization laboratory. By systematic use of FFR in dubious stenosis and multi-vessel disease, PCI can be made an even more effective and better treatment than it is currently. The current clinical evidence for FFR should encourage cardiologists to use this tool in the catheterization laboratory.

New horizons in cardiac CT

Until recently, cardiovascular computed tomography angiography (CCTA) was associated with considerable radiation doses. The introduction of tube current modulation and automatic tube potential selection as well as high-pitch prospective ECG-triggering and iterative reconstruction offer the ability to decrease dose with approximately one order of magnitude, often to sub-millisievert dose levels. In parallel, advancements in computational technology have enabled the measurement of fractional flow reserve (FFR) from CCTA data (FFRCT). This technique shows potential to replace invasively measured FFR to select patients in need of coronary intervention. Furthermore, developments in scanner hardware have led to the introduction of dual-energy and photon-counting CT, which offer the possibility of material decomposition imaging. Dual-energy CT reduces beam hardening, which enables CCTA in patients with a high calcium burden and more robust myocardial CT perfusion imaging. Future-generation CT systems will be capable of counting individual X-ray photons. Photon-counting CT is promising and may result in a substantial further radiation dose reduction, vastly increased spatial resolution, and the introduction of a whole new class of contrast agents.

Coronary Computed Tomography Angiography Derived Fractional Flow Reserve and Plaque Stress

Fractional flow reserve (FFR) measured during invasive coronary angiography is an independent prognosticator in patients with coronary artery disease and the gold standard for decision making in coronary revascularization. The integration of computational fluid dynamics and quantitative anatomic and physiologic modeling now enables simulation of patient-specific hemodynamic parameters including blood velocity, pressure, pressure gradients, and FFR from standard acquired coronary computed tomography (CT) datasets. In this review article, we describe the potential impact on clinical practice and the science behind noninvasive coronary computed tomography (CT) angiography derived fractional flow reserve (FFR_CT) as well as future applications of this technology in treatment planning and quantifying forces on atherosclerotic plaques.

Comparison of Approaches to Revascularization in Patients With Multivessel Coronary Artery Disease Presenting With ST-Segment Elevation Myocardial Infarction: Meta-analyses of Randomized Control Trials

BACKGROUND

Significant controversy exists regarding the best approach for nonculprit vessel revascularization in patients with multivessel coronary artery disease presenting with ST-segment elevation myocardial infarction. We conducted a systematic investigation to pool data from current randomized controlled trials (RCTs) to assess optimal treatment strategies in this patient population.

METHODS AND RESULTS

A comprehensive search of SCOPUS from inception through May 2015 was performed using predefined criteria. We compared efficacy and safety outcomes of different approaches by categorizing the studies into 3 groups: (1) complete revascularization (CR) versus culprit lesion revascularization (CL) at index hospitalization, (2) CR at index hospitalization versus staged revascularization (SR) of nonculprit vessels at a separate hospitalization, and (3) comparison of SR versus CL. Eight eligible RCTs met the inclusion criteria: (1) CR versus CL (6 RCTs, n=1727) (2) CR versus SR (3 RCTs, n=311), and (3) SR versus CL (1 RCT, n=149). We observed significantly lower rates of major adverse cardiovascular events, revascularization, and repeat percutaneous coronary interventions among patients treated with CR and SR compared with a CL approach (P<0.05). The rates of all-cause mortality, cause-specific mortality, major bleeding, reinfarction, stroke, and contrast-induced nephropathy did not differ in the CR arm compared with the CL arm. The rates of these outcomes were similar in the CR and SR arms.

CONCLUSION

Results suggest that CR and SR compared with CL reduce major adverse cardiovascular event and revascularization rates primarily by lowering repeated percutaneous coronary intervention rates. We did not observe any increase in the rate of adverse events while using a CR or SR strategy compared with a CL approach. Current guidelines discouraging CR need to be reevaluated, and clinical judgment should prevail in treating multivessel coronary artery disease patients with ST-segment elevation myocardial infarction as data from larger RCTs accumulate.

Rationale and design of the dual-energy computed tomography for ischemia determination compared to "gold standard" non-invasive and invasive techniques (DECIDE-Gold): A multicenter international efficacy diagnostic study of rest-stress dual-energy computed tomography angiography with perfusion

BACKGROUND

Dual-energy CT (DECT) has potential to improve myocardial perfusion for physiologic assessment of coronary artery disease (CAD). Diagnostic performance of rest-stress DECT perfusion (DECTP) is unknown.

OBJECTIVE

DECIDE-Gold is a prospective multicenter study to evaluate the accuracy of DECT to detect hemodynamic (HD) significant CAD, as compared to fractional flow reserve (FFR) as a reference standard.

METHODS

Eligible participants are subjects with symptoms of CAD referred for invasive coronary angiography (ICA). Participants will undergo DECTP, which will be performed by pharmacological stress, and participants will subsequently proceed to ICA and FFR. HD-significant CAD will be defined as FFR ≤ 0.80. In those undergoing myocardial stress imaging (MPI) by positron emission tomography (PET), single photon emission computed tomography (SPECT) or cardiac magnetic resonance (CMR) imaging, ischemia will be graded by % ischemic myocardium. Blinded core laboratory interpretation will be performed for CCTA, DECTP, MPI, ICA, and FFR.

RESULTS

Primary endpoint is accuracy of DECTP to detect ≥1 HD-significant stenosis at the subject level when compared to FFR. Secondary and tertiary endpoints are accuracies of combinations of DECTP at the subject and vessel levels compared to FFR and MPI.

CONCLUSION

DECIDE-Gold will determine the performance of DECTP for diagnosing ischemia.

Comprehensive assessment of coronary fractional flow reserve

Fractional flow reserve (FFR) is considered nowadays as the gold standard for invasive assessment of physiologic stenosis significance and an indispensable tool for decision-making in coronary revascularization. Robust studies have shown that FFR is more effective in accurately identifying which lesions should be stented, and revascularization guided by FFR improves the outcome of coronary artery disease in patients. Therefore, FFR has been upgraded to a class A recommendation in current guidelines when the ischemic potential for specific target lesions is controversial. This article reviews the laboratory practice, functional evaluation of FFR as a gold standard and its emerging clinical application. In addition, novel noninvasive technologies of FFR measurement are discussed in depth.

Diagnostic accuracy of stress myocardial perfusion imaging compared to invasive coronary angiography with fractional flow reserve meta-analysis

BACKGROUND

Hemodynamically significant coronary artery disease is an important indication for revascularization. Stress myocardial perfusion imaging is a noninvasive alternative to invasive fractional flow reserve for evaluating hemodynamically significant coronary artery disease. The aim was to determine the diagnostic accuracy of myocardial perfusion imaging by single-photon emission computed tomography, echocardiography, MRI, positron emission tomography, and computed tomography compared with invasive coronary angiography with fractional flow reserve for the diagnosis of hemodynamically significant coronary artery disease.

METHODS AND RESULTS

The meta-analysis adhered to the Preferred Reporting Items for Systematic Reviews and Meta-analyses statement. PubMed, EMBASE, and Web of Science were searched until May 2014. Thirty-seven studies, reporting on 4721 vessels and 2048 patients, were included. Meta-analysis yielded pooled sensitivity, pooled specificity, pooled likelihood ratios (LR), pooled diagnostic odds ratio, and summary area under the receiver operating characteristic curve. The negative LR (NLR) was chosen as the primary outcome. At the vessel level, MRI (pooled NLR, 0.16; 95% confidence interval [CI], 0.13-0.21) was performed similar to computed tomography (pooled NLR, 0.22; 95% CI, 0.12-0.39) and positron emission tomography (pooled NLR, 0.15; 95% CI, 0.05-0.44), and better than single-photon emission computed tomography (pooled NLR, 0.47; 95% CI, 0.37-0.59). At the patient level, MRI (pooled NLR, 0.14; 95% CI, 0.10-0.18) performed similar to computed tomography (pooled NLR, 0.12; 95% CI, 0.04-0.33) and positron emission tomography (pooled NLR, 0.14; 95% CI, 0.02-0.87), and better than single-photon emission computed tomography (pooled NLR, 0.39; 95% CI, 0.27-0.55) and echocardiography (pooled NLR, 0.42; 95% CI, 0.30-0.59).

CONCLUSIONS

Stress myocardial perfusion imaging with MRI, computed tomography, or positron emission tomography can accurately rule out hemodynamically significant coronary artery disease and can act as a gatekeeper for invasive revascularization. Single-photon emission computed tomography and echocardiography are less suited for this purpose.

Low dose dynamic myocardial CT perfusion using advanced iterative reconstruction

Dynamic myocardial CT perfusion (CTP) can provide quantitative functional information for the assessment of coronary artery disease. However, x-ray dose in dynamic CTP is high, typically from 10mSv to >20mSv. We compared the dose reduction potential of advanced iterative reconstruction, Iterative Model Reconstruction (IMR, Philips Healthcare, Cleveland, Ohio) to hybrid iterative reconstruction (iDose4) and filtered back projection (FBP). Dynamic CTP scans were obtained using a porcine model with balloon-induced ischemia in the left anterior descending coronary artery to prescribed fractional flow reserve values. High dose dynamic CTP scans were acquired at 100kVp/100mAs with effective dose of 23mSv. Low dose scans at 75mAs, 50mAs, and 25mAs were simulated by adding x-ray quantum noise and detector electronic noise to the projection space data. Images were reconstructed with FBP, iDose4, and IMR at each dose level. Image quality in static CTP images was assessed by SNR and CNR. Blood flow was obtained using a dynamic CTP analysis pipeline and blood flow image quality was assessed using flow-SNR and flow-CNR. IMR showed highest static image quality according to SNR and CNR. Blood flow in FBP was increasingly over-estimated at reduced dose. Flow was more consistent for iDose4 from 100mAs to 50mAs, but was over-estimated at 25mAs. IMR was most consistent from 100mAs to 25mAs. Static images and flow maps for 100mAs FBP, 50mAs iDose4, and 25mAs IMR showed comparable, clear ischemia, CNR, and flow-CNR values. These results suggest that IMR can enable dynamic CTP at significantly reduced dose, at 5.8mSv or 25% of the comparable 23mSv FBP protocol.

Fractional flow reserve in acute coronary syndromes: A review

Fractional flow reserve (FFR) assessment provides anatomical and physiological information that is often used to tailor treatment strategies in coronary artery disease. Whilst robust data validates FFR use in stable ischaemic heart disease, its use in acute coronary syndromes (ACS) is less well investigated. We critically review the current data surrounding FFR use across the spectrum of ACS including culprit and non-culprit artery analysis. With adenosine being conventionally used to induce maximal hyperaemia during FFR assessment, co-existent clinical conditions may preclude its use during acute myocardial infarction. Therefore, we include a current review of instantaneous wave free ratio as a novel vasodilator independent method of assessing lesion severity as an alternative strategy to guide revascularisation in ACS.

•

Small studies support the use of FFR in non-culprit vessels during ACS.

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FFR demonstrates diagnostic accuracy and reproducibility in AMI, particularly in intermediate lesions.

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Microvascular dysfunction observed from earlier work does not appear to hinder FFR calculation, but further studies are required for validation.

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Vasodilator independent assessment of coronary stenoses has some preliminary data supporting its use in non culprit arteries during ACS, but ongoing trial results are awaited regarding clinical outcomes.

Impact of microvascular obstruction on the assessment of coronary flow reserve, index of microcirculatory resistance, and fractional flow reserve after ST-segment elevation myocardial infarction

BACKGROUND

Invasive assessment of coronary physiology (IACP) offers important prognostic insights in ST-segment elevation myocardial infarction (STEMI) but the dynamics of coronary recovery are poorly understood.

OBJECTIVES

This study sought to examine the evolution of coronary flow reserve (CFR), index of microcirculatory resistance (IMR), ratio of distal coronary pressure (Pd) to mean aortic pressure (Pa), and fractional flow reserve (FFR) in patients undergoing primary percutaneous coronary intervention (PPCI).

METHODS

82 patients with STEMI underwent IACP at PPCI. Repeat IACP was performed in 61 patients (74%) at day 1 and in 46 patients (56%) at 6 months. Contrast-enhanced cardiac magnetic resonance imaging (CMR) was performed in 45 patients (55%) at day 1 and in 41 patients (50%) at 6 months. Changes in IACP were compared between patients with and without microvascular obstruction (MVO) on CMR.

RESULTS

MVO was present in 21 of 45 patients (47%). Patients with MVO had lower CFR at PPCI and day 1 (p < 0.05) and a trend toward higher IMR values (p = 0.07). At 6 months, CFR and IMR were not significantly different between the groups. Baseline flow and Pd/Pa remained stable over time but FFR reduced significantly between PPCI and 6 months (p = 0.008); this reduction was mainly observed in patients with MVO (p = 0.006) but not in those without MVO (p = 0.21).

CONCLUSIONS

In PPCI-treated patients with STEMI, coronary microcirculation begins to recover within 24 h and recovery progresses further by 6 months. FFR significantly reduces from baseline to 6 months. The presence of MVO indicates a highly dysfunctional microcirculation.

Determination of culprit coronary artery branches using hemodynamic indices from angiographic images

A recently reported angiographic technique for hemodynamic indices based on first-pass distribution analysis (FPA) could potentially be helpful for determining the culprit artery responsible for myocardial ischemia. The purpose of this study was to determinate the culprit coronary arterial branches based on coronary flow reserve (CFR) and fractional flow reserve (FFR) using only angiographic images. The study was performed in 14 anesthetized swine. Microspheres were injected into coronary arterial branches to create microvascular disruption. Stenosis was also created by inserting plastic tubings in LAD and LCX arterial branches. Adenosine was used to produce maximum hyperemia. Angiographic CFR (CFRa), relative angiographic CFR (rCFRa), and angiographic FFR (FFRa) were calculated by FPA. The diagnostic abilities of CFRa, rCFRa, and FFRa were compared in three models: (1) epicardial stenosis model (S), (2) microcirculation disruption model (M), and (3) combined(S + M) model by using the area under the ROC curve (AUC). The mean differences between FFRa and the pressure-derived FFR (FFRp) measurements were -0.01 ± 0.21 in S model (N = 37) and 0.01 ± 0.18 in M model (N = 53). From 225 measurements in S model, the AUCs for CFRa and FFRa were 0.720 and 0.918, respectively. From 262 measurements in M model and 238 measurements in (S + M) model, the AUCs for CFRa, rCFRa, FFRa were 0.744, 0.715, 0.959 and 0.806, 0.738, 0.995, respectively. The hemodynamic indices of the small branches (down to ~0.7 mm) could be measured using only angiographic image data. The application of FFRa could potentially provide a useful method to assess the severity of disease in coronary arterial branches.

The value of assessing myocardial deformation at recovery after dobutamine stress echocardiography

Background

The purpose of this study was to evaluate whether performing an assessment of myocardial deformation using speckle tracking imaging during the recovery period after dobutamine stress echocardiography (DSE) allows detection of significant coronary artery disease (CAD) in patients with chest discomfort.

Methods

DSE and coronary angiography were performed in 44 patients with chest discomfort. The mean global longitudinal peak systolic strain (GLS) was measured at rest, at low stress (dobutamine infusion rate of 10 µg/kg/min) and at recovery (5 min after cessation of dobutamine infusion) of DSE using automated function imaging with apical views. Fractional flow reserve (FFR) was also performed in patients with intermediate coronary stenosis. CAD was defined as having a ≥ 70% diameter stenosis on coronary angiography or as having a FFR < 0.8. Patients were divided two groups based on the absence or presence of CAD [CAD (-) group vs. CAD (+) group].

Results

There were no significant differences in the clinical characteristics and results of conventional echocardiography between the two groups. GLS at recovery was lower in the CAD (+) group than in the CAD (-) group (-18.0 ± 3.4% vs. -21.0 ± 1.9%, p = 0.003). The optimal cutoff of GLS at recovery for detection of CAD was -19% (sensitivity of 70.6%, specificity of 83.3%).

Conclusion

Assessment of GLS at recovery of DSE is a reliable and objective method for detection of CAD. This finding may suggest that systolic myocardial stunning remains even after recovery of wall motion abnormalities in patients with CAD.

Potential influence of invisible coronary collateral circulation on fractional flow reserve of donor artery in the presence of severe stenosis of receiving artery

We reported a case of 78-year-old male who had a severe stenosis in the right coronary artery (RCA) and an intermediate stenosis in the left anterior descending artery (LAD) without visible collateral flow to the RCA on angiogram. Fractional flow reserve (FFR) in the LAD lesion, which revealed significant value as 0.70, increased to 0.78 after revascularization of the RCA lesion. The FFR in an intermediate stenosis should be performed after PCI for severe stenosis in the other coronary arteries. Otherwise, the severity of the stenosis could be overestimated due to the presence of invisible collateral circulation.

Computational fluid dynamics modeling of symptomatic intracranial atherosclerosis may predict risk of stroke recurrence

BACKGROUND

Patients with symptomatic intracranial atherosclerosis (ICAS) of ≥ 70% luminal stenosis are at high risk of stroke recurrence. We aimed to evaluate the relationships between hemodynamics of ICAS revealed by computational fluid dynamics (CFD) models and risk of stroke recurrence in this patient subset.

METHODS

Patients with a symptomatic ICAS lesion of 70-99% luminal stenosis were screened and enrolled in this study. CFD models were reconstructed based on baseline computed tomographic angiography (CTA) source images, to reveal hemodynamics of the qualifying symptomatic ICAS lesions. Change of pressures across a lesion was represented by the ratio of post- and pre-stenotic pressures. Change of shear strain rates (SSR) across a lesion was represented by the ratio of SSRs at the stenotic throat and proximal normal vessel segment, similar for the change of flow velocities. Patients were followed up for 1 year.

RESULTS

Overall, 32 patients (median age 65; 59.4% males) were recruited. The median pressure, SSR and velocity ratios for the ICAS lesions were 0.40 (-2.46-0.79), 4.5 (2.2-20.6), and 7.4 (5.2-12.5), respectively. SSR ratio (hazard ratio [HR] 1.027; 95% confidence interval [CI], 1.004-1.051; P = 0.023) and velocity ratio (HR 1.029; 95% CI, 1.002-1.056; P = 0.035) were significantly related to recurrent territorial ischemic stroke within 1 year by univariate Cox regression, respectively with the c-statistics of 0.776 (95% CI, 0.594-0.903; P = 0.014) and 0.776 (95% CI, 0.594-0.903; P = 0.002) in receiver operating characteristic analysis.

CONCLUSIONS

Hemodynamics of ICAS on CFD models reconstructed from routinely obtained CTA images may predict subsequent stroke recurrence in patients with a symptomatic ICAS lesion of 70-99% luminal stenosis.

Myocardial ischemia is a key factor in the management of stable coronary artery disease

Previous studies demonstrated that coronary revascularization, especially percutaneous coronary intervention (PCI), does not significantly decrease the incidence of cardiac death or myocardial infarction in patients with stable coronary artery disease. Many studies using myocardial perfusion imaging (MPI) showed that, for patients with moderate to severe ischemia, revascularization is the preferred therapy for survival benefit, whereas for patients with no to mild ischemia, medical therapy is the main choice, and revascularization is associated with increased mortality. There is some evidence that revascularization in patients with no or mild ischemia is likely to result in worsened ischemia, which is associated with increased mortality. Studies using fractional flow reserve (FFR) demonstrate that ischemia-guided PCI is superior to angiography-guided PCI, and the presence of ischemia is the key to decision-making for PCI. Complementary use of noninvasive MPI and invasive FFR would be important to compensate for each method's limitations. Recent studies of appropriateness criteria showed that, although PCI in the acute setting and coronary bypass surgery are properly performed in most patients, PCI in the non-acute setting is often inappropriate, and stress testing to identify myocardial ischemia is performed in less than half of patients. Also, some studies suggested that revascularization in an inappropriate setting is not associated with improved prognosis. Taken together, the presence and the extent of myocardial ischemia is a key factor in the management of patients with stable coronary artery disease, and coronary revascularization in the absence of myocardial ischemia is associated with worsened prognosis.

Diagnostic accuracy of intravascular ultrasound-derived minimal lumen area compared with fractional flow reserve--meta-analysis: pooled accuracy of IVUS luminal area versus FFR

INTRODUCTION

Although intravascular ultrasound minimal luminal area (IVUS-MLA) is one of many anatomic determinants of lesion severity, it has been proposed as an alternative to fractional flow reserve (FFR) to assess severity of coronary artery disease.

OBJECTIVE

Pool the diagnostic performance of IVUS-MLA and determine its overall accuracy to predict the functional significance of coronary disease using FFR (0.75 or 0.80) as the gold standard.

METHODS

Studies comparing IVUS and FFR to establish the best MLA cutoff value that correlates with significant coronary stenosis were reviewed from a Medline search using the terms "fractional flow reserve" and "ultrasound." DerSimonian Laird method was applied to obtain pooled accuracy.

RESULTS

Eleven clinical trials, including two left main (LM) trials (total N = 1,759 patients, 1,953 lesions) were included. The weighted overall mean MLA cutoff was 2.61 mm(2) in non-LM trials and 5.35 mm(2) in LM trials. For non-LM lesions, the pooled sensitivity of MLA was 0.79 (95% CI = 0.76-0.83) and specificity was 0.65 (95% CI = 0.62-0.67). Positive likelihood ratio (LR) was 2.26 (95% CI = 1.98-2.57) and LR- was 0.32 (95% CI = 0.24-0.44). Area under the summary receiver operator curve for all trials was 0.848. Pooled LM trials had better accuracy: sensitivity = 0.90, specificity = 0.90, LR+ = 8.79, and LR- = 0.120.

CONCLUSION

Given its limited pooled accuracy, IVUS-MLA's impact on clinical decision in this scenario is low and may lead to misclassification in up to 20% of the lesions. Pooled analysis points toward lower MLA cutoffs than the ones used in current practice.

ST elevation after intracoronary administration of Papaverine for fractional flow reserve estimation

INTRODUCTION

Intracoronary (IC) papaverine which is one of the commonly used agents for Fractional Flow Reserve (FFR) estimation has been reported to cause transient ST elevation in some patients. This phenomenon has not been systematically studied.

MATERIAL AND METHODS

This is a prospective, observational study. Consecutive patients, who underwent FFR at our institute using IC papaverine from May 2012 to April 2013, were included. FFR was done when clinically indicated. The procedure involved administration of 20 mg papaverine (Paparin)--Troikaa, Ahmedabad) as a fast bolus by intracoronary route followed by a 10 cc contrast flush, following which pressure measurements were made. Continuous ECG recording by Philips Hemodynamic Laboratory was obtained for all patients throughout the procedure. Post procedure, they were observed for any delayed effects and eventual outcome was documented. Fischer's mid-p test was used for statistical analysis.

RESULT

Twenty-five patients (18 males, 7 females, mean age 57.9 ± 20 years) underwent FFR using Papaverine. The mean LVEF was (51 ± 15%). Fourteen patients (56%) developed transient ST elevation ≥0.5 mm in one or more leads which resolved spontaneously in all cases without any sequelae. The presence of a significant lesion either in the coronary artery being evaluated or in a remote coronary artery did not predict the ST elevation. 70.5% of diabetics (p = 0.02), 75% of hypertensives (p = 0.008) and 75% of patients with LVH (p = 0.008) had ST elevation. None of the 5 patients without any one of these comorbidities showed ST elevation.

CONCLUSION

Transient ST elevation occurs in a significant proportion of cases receiving IC papaverine which is not associated with any adverse clinical outcomes. Micro vascular dysfunction is the most likely mechanism of this phenomenon.

Three-dimensional quantitative coronary angiography and quantification of jeopardised myocardium to predict functional significance of intermediate coronary artery stenosis

AIMS

Despite the fact that fractional flow reserve (FFR) is better than angiography in guiding PCI, in the real world the choice to perform PCI is generally based on angiography. Three-dimensional quantitative coronary angiography (3D-QCA) may increase the accuracy of angiography, especially in intermediate coronary artery stenosis (ICAS). The aim of the study was to assess the best cut-off values of area stenosis % (AS%) and the extent of jeopardised myocardium for predicting FFR and for excluding the need to perform FFR.

METHODS AND RESULTS

FFR, AS% and Myocardial Jeopardy Index (MJI) were assessed in 211 ICAS. MJI (=-0.36; p=0.001), AS% (=-0.35; p=0.001) and presence of a chronic total occlusion (CTO) (=-0.15; p=0.01) were independent predictors of FFR. In patients without CTO (174 lesions), the best cut-offs for the detection of FFR ≤0.80 for AS% and MJI were 61% (AUC=0.76; p<0.001) and 30% (AUC=0.71; p<0.001), respectively. More importantly, the cut-offs of AS% safely to exclude (100% sensitivity) an FFR ≤0.80 were 40% (AUC=0.85, p<0.001) for an MJI ≥30% and 50% (AUC=0.70, p<0.04) for an MJI <30%, respectively.

CONCLUSIONS

AS%, MJI and the presence of a CTO predicted FFR values. 3D-QCA in addition to MJI allows the safe exclusion of FFR ≤0.80, limiting FFR assessment to doubtful cases with considerable reduction of costs.

Intracoronary versus intravenous adenosine-induced maximal coronary hyperemia for fractional flow reserve measurements

BACKGROUND

Maximal hyperemia is the critical prerequisite for fractional flow reserve (FFR) assessment. Despite intravenous (IV) adenosine currently being the recommended approach, intracoronary (IC) administration of adenosine constitutes a valuable alternative in everyday practice. However, it is surprisingly unclear which IC strategy allows the achievement of FFR values that are comparable to IV adenosine.

OBJECTIVES

This study sought to compare increasing doses of IC adenosine versus IV adenosine for FFR.

METHODS

30 intermediate coronary stenoses undergoing FFR measurement were prospectively and consecutively enrolled. Hyperemia was sequentially induced by bolus of IC adenosine (ADN; 150 μg) followed by IV adenosine (IVADN) infusion over 3 minutes at dose of (140 μg/kg/min). FFR values, symptoms, and development of atrioventricular block were recorded.

RESULTS

150 μg doses of IC adenosine were well tolerated and associated with fewer symptoms than IV adenosine. Intracoronary adenosine doses induced a significant decrease of FFR compared with baseline levels (P < 0.01). Among the 6 patients with FFR values less than 0.80 identified by IVADN, 4 were correctly identified also by 150 μg bolus IC adenosine. Larger randomized studies with cross-over design are necessary to verify the results.

CONCLUSIONS

This small pilot study suggests that IC adenosine might be an alternative to IV adenosine. Larger randomized studies with a cross-over design are necessary.

Fractional Flow Reserve Derived from Coronary Imaging and Computational Fluid Dynamics

The assessment of functional severity of atherosclerotic stenoses in patients with coronary artery disease by invasive fractional flow reserve (FFR) measurement requires coronary artery cannulation, advancement of a wire and intravenous adenosine infusion with inherent procedure-related risk and costs. Coronary computed tomographic angiography (CCTA) and rotational coronary angiography (RA) have been recently used in conjunction with computational fluid dynamics (CFD) and image-based modelling for the determination of FFR without the need for additional imaging, modification of acquisition protocols or administration of medication. FFR derived from CCTA was demonstrated as superior to measures of CCTA stenosis severity for determination of lesion-specific ischaemia. Estimation of FFR from RA images and CFD provides a less invasive alternative to conventional FFR measurement while estimated values are in agreement with measured values. These new, combined anatomic-functional assessments have the potential to simplify the noninvasive diagnosis of coronary artery disease with a single study to identify patients with ischaemia-causing stenosis who may benefit from revascularisation.

The relationship between fractional flow reserve, platelet reactivity and platelet leukocyte complexes in stable coronary artery disease

BACKGROUND

The presence of stenoses that significantly impair blood flow and cause myocardial ischemia negatively affects prognosis of patients with stable coronary artery disease. Altered platelet reactivity has been associated with impaired prognosis of stable coronary artery disease. Platelets are activated and form complexes with leukocytes in response to microshear gradients caused by friction forces on the arterial wall or flow separation. We hypothesized that the presence of significantly flow-limiting stenoses is associated with altered platelet reactivity and formation of platelet-leukocyte complexes.

METHODS

One hundred patients with stable angina were studied. Hemodynamic significance of all coronary stenoses was assessed with Fractional Flow Reserve (FFR). Patients were classified FFR-positive (at least one lesion with FFR≤0.75) or FFR-negative (all lesions FFR>0.80). Whole blood samples were stimulated with increasing concentrations of ADP, TRAP, CRP and Iloprost with substimulatory ADP. Expression of P-selectin as platelet activation marker and platelet-leukocyte complexes were measured by flowcytometry. Patients were stratified on clopidogrel use. FFR positive and negative patient groups were compared on platelet reactivity and platelet-leukocyte complexes.

RESULTS

Platelet reactivity between FFR-positive patients and FFR-negative patients did not differ. A significantly lower percentage of circulating platelet-neutrophil complexes in FFR-positive patients and a similar non-significant decrease in percentage of circulating platelet-monocyte complexes in FFR-positive patients was observed.

CONCLUSION

The presence of hemodynamically significant coronary stenoses does not alter platelet reactivity but is associated with reduced platelet-neutrophil complexes in peripheral blood of patients with stable coronary artery disease.

Quantitative angiography and optical coherence tomography for the functional assessment of nonobstructive coronary stenoses: comparison with fractional flow reserve

BACKGROUND

The purpose was to compare 3-dimensional quantitative coronary angiography (3D-QCA) with optical coherence tomography (OCT) for the functional assessment of nonobstructive coronary stenoses, as evaluated by fractional flow reserve (FFR).

METHODS

Fifty-five nonobstructive coronary stenoses (30%-50% diameter stenosis by visual estimation) were assessed in 36 patients using FFR, 2-dimensional QCA (2D-QCA), 3D-QCA, and OCT.

RESULTS

Angiographic stenosis severity by 2D-QCA was 34% ± 13% diameter stenosis, and minimal lumen diameter (MLD) was 1.77 ± 0.58 mm. Fractional flow reserve values were 0.85 ± 0.10. Correlation coefficients between FFR and MLD or minimal lumen area (MLA) were highly significant for both 2D- and 3D-QCA (all P < .001), but higher R(2) values were observed for 3D-QCA measurements. Although significant, correlation coefficients between OCT and FFR data were weak (R(2) = 0.28, P = .001 for MLD and R(2) = 0.23, P = .003 for MLA). Correlation coefficients with FFR were significantly higher for 3D-QCA than for OCT (P values for MLD and MLA = .043 and .042, respectively). Nonobstructive stenoses with MLD >1.53 mm or MLA >2.43 mm(2) are unlikely to be hemodynamically significant.

CONCLUSIONS

In nonobstructive coronary stenoses, anatomical parameters derived from 3D-QCA can best identify lesions with preserved FFR values.

Interobserver reproducibility of signal intensity ratio on magnetic resonance angiography for hemodynamic impact of intracranial atherosclerosis

BACKGROUND

Changes of signal intensities (SIs) across intracranial atherosclerosis (ICAS) on magnetic resonance angiography (MRA) may reflect hemodynamic impact of the lesion. We evaluated the interobserver reproducibility of an index termed signal intensity ratio (SIR), developed in a previous study to represent the changes of SIs across ICAS on MRA.

METHODS

Symptomatic ICAS on MRA were retrospectively recruited. Two observers respectively evaluated the images and calculated the SIR as follows, blinded to each other's readings: SIR=(mean poststenotic SI-mean background SI)/(mean prestenotic SI-mean background SI). Statistical analyses were performed to evaluate the interobserver reproducibility of this index.

RESULTS

A total of 102 symptomatic ICASs were enrolled, with 36 (35.3%) lesions of 50%-69% MRA stenoses and others being 70%-99% stenoses or flow void on MRA. Overall, mean SIRs were not significantly different between the 2 observers (.92±.17 versus .93±.17; mean difference -.006±.09; P=.496 for paired t test). Pearson correlation coefficients were >.80 for all analyses, indicating strong linear correlations between SIRs by the 2 observers. Bland-Altman analysis for SIRs of all cases showed no systematic bias between the 2 observers. For different cut-points ranging from .75 to 1.00, the kappa statistics were mostly greater than .6 and interobserver agreements were all greater than 80%, implying substantial agreement between observers.

CONCLUSIONS

SIR was demonstrated to be highly reproducible between observers in the present study. Future studies are warranted to further explore the role of this index in comprehensive evaluation and risk stratification of symptomatic ICAS.

Optical coherence tomography criteria for defining functional severity of intermediate lesions: a comparative study with FFR

Fractional flow reserve (FFR) is the gold standard in the assessment of severity of the coronary stenosis. The aim of the study was to compare optical coherence tomography (OCT) obtained intermediate coronary lesions lumen areas measurements with FFR assessments, with the goal to develop an OCT threshold to identify significant coronary stenosis. 48 patients (mean age 65 ± 10 years) was enrolled for the study. Within this population, 71 intermediate coronary lesions were investigated using both FFR and OCT. High dose bolus of Adenosine (120 μg) was used to obtain coronary hyperemia. OCT imaging was performed using non-occlusive technique to assess minimal lumen area (MLA) and diameter. The OCT cut-off value that showed the best correlation with the FFR cut-off of 0.80 was the MLA less than 2.05 mm2 (accuracy 87%, sensitivity 75%, specificity 90%, p < 0.001). The study did not disclose any relationship between FFR value and the lesion length. Vessel size influenced the OCT cut-off values, with greater values being found in presence of arteries with a reference diameter greater than 3.0 mm. OCT derived minimal lumen area might be complementary to FFR measurement in identifying ischemia related lesions. Further studies are warranted to assess threshold values in relation to vessel size and location.

Correlation between intracoronary ultrasound and fractional flow reserve in long coronary lesions. A three-dimensional intracoronary ultrasound study

INTRODUCTION AND OBJECTIVES

Intracoronary ultrasound estimation of the functional significance of intermediate angiographic lesions has mainly been based on measuring the minimal lumen area. These estimates take no account of lesion length and pay insufficient attention to long coronary lesions.

METHODS

We included 61 lesions with visual angiographic stenosis of 40% to 70% that required treatment with a ≥20mm stent, studied with ultrasound and fractional flow reserve. Three-dimensional analysis of the ultrasound study was conducted offline and blinded to fractional reserve values. Angiographic and ultrasound parameters were correlated with fractional reserve.

RESULTS

From the angiography we obtained data on mean reference diameter (2.87 [0.57] mm), length (29.8 [10.01] mm), and severity of stenosis (50.3% [8.7]%). Mean fractional flow reserve was 0.78 (0.09). We found a weak linear correlation (R) between fractional reserve and the ultrasound parameters that did not include lesion length: fractional reserve-minimal luminal area (R=0.4; P=.003). The correlation was stronger when lesion length was included: fractional reserve-volume of plaque (R=-0.65; P<.0005); fractional reserve-length/mean luminal area (R=0.73; P<.0005). The strongest correlation came from the product of mean stenosis by area multiplied by lesion length (R=-0.78; P<.0005).

CONCLUSIONS

In long coronary lesions, the correlation between ultrasound-measured minimal lumen area and functional significance is weak. In these cases, estimates of functional significance should incorporate lesion length or be derived from direct fractional flow reserve measurement.

Long-term clinical outcome after fractional flow reserve- versus angio-guided percutaneous coronary intervention in patients with intermediate stenosis of coronary artery bypass grafts

BACKGROUND

Fractional flow reserve (FFR)-guided percutaneous revascularization (percutaneous coronary intervention [PCI]) of intermediate stenosis in native coronary artery is safe and associated with better clinical outcomes as compared with an angiography-guided PCI. It is unknown whether this applies to coronary artery bypass grafts (CABGs).

METHODS

We included 223 patients with CABG and with stable or unstable angina and an intermediate stenosis involving an arterial or a venous graft. Patients were divided into 2 groups: FFR guided (n = 65, PCI performed in case of FFR ≤0.80) and angio guided (n = 158, PCI performed based on angiographic evaluation). Primary end point was major adverse cardiac and cerebrovascular event, defined as death, myocardial infarction, target vessel failure, and cerebrovascular accident (CVA).

RESULTS

The 2 groups were similar in terms of demographic and clinical characteristics. Percutaneous coronary intervention was performed in 23 patients (35%) of the FFR-guided group and 90 patients (57%) of the angio-guided group (P < .01). In the FFR-guided group, PCI was more often performed in arterial grafts as compared with the angio-guided group (16 [70%] vs 12 [13%], respectively; P < .01). Follow-up was obtained in 96% of patients at a median of 3.8 years (1.6-4.0 years). At multivariate analysis, major adverse cardiac and cerebrovascular event rate was significantly lower in the FFR-guided group as compared with the angio-guided group (18 [28%] vs 77 [51%], hazard ratio 0.33 [0.11-0.96], P = .043]. Procedure costs were overall reduced in the FFR-guided group (€2240 ± €652 vs €2416 ± €522, P = .03).

CONCLUSIONS

An FFR-guided PCI of intermediate stenosis in bypass grafts is safe and results in better clinical outcomes as compared with an angio-guided PCI. This clinical benefit is achieved with a significant overall reduction in procedural costs.

Association of biomarkers of lipid modification with functional and morphological indices of coronary stenosis severity in stable coronary artery disease

Biomarkers of blood lipid modification and oxidative stress have been associated with increased cardiovascular morbidity. We sought to determine whether these biomarkers were related to functional indices of stenosis severity among patients with stable coronary artery disease. We studied 197 consecutive patients with stable coronary artery disease due to single vessel disease. Fractional flow reserve (FFR) ≤ 0.80 was assessed as index of a functionally significant lesion. Serum levels of secretory phospholipase A2 (sPLA2) activity, secretory phospholipase A2 type IIA (sPLA2-IIA), myeloperoxydase (MPO), lipoprotein-associated phospholipase A2 (Lp-PLA2), and oxidized low-density lipoprotein (OxLDL) were assessed using commercially available assays. Patients with FFR > 0.8 had higher sPLA2 activity, sPLA2 IIA, and OxLDL levels than patients with FFR ≤ 0.8 (21.25 [16.03-27.28] vs 25.85 [20.58-34.63] U/mL, p < 0.001, 2.0 [1.5-3.4] vs 2.6 [2.0-3.4] ng/mL, p < 0.01; and 53.0 [36.0-71.0] vs 64.5 [50-89.25], p < 0.001 respectively). Patients with FFR > 0.80 had similar Lp-PLA2 and MPO levels versus those with FFR ≤ 0.8. sPLA2 activity, sPLA2 IIA significantly increased area under the curve over baseline characteristics to predict FFR ≤ 0.8 (0.67 to 0.77 (95 % confidence interval [CI]: 0.69-0.85) p < 0.01 and 0.67 to 0.77 (95 % CI: 0.69-0.84) p < 0.01, respectively). Serum sPLA2 activity as well as sPLA2-IIA level is related to functional characteristics of coronary stenoses in patients with stable coronary artery disease.

Comparison of effectiveness of high-dose intracoronary adenosine versus intravenous administration on the assessment of fractional flow reserve in patients with coronary heart disease

Intravenous adenosine is considered the drug of choice to obtain maximum hyperemia in the measurement of the fractional flow reserve (FFR). However, comparative studies performed between intravenous and intracoronary administration have not used high doses of intracoronary adenosine. The present study compared the efficacy and safety of high doses of intracoronary adenosine to intravenous administration when calculating the FFR. Intracoronary bolus doses of 60, 180, 300, and 600 μg adenosine were compared to an intravenous administration of 140 μg/kg/min, 200 μg/kg/min, and 140 μg/kg/min plus an intracoronary bolus of 120 μg. All the cases were performed using the radial approach. FFR was assessed in 102 patients with 108 intermediate lesions by an intracoronary pressure wire. The intracoronary dose of 60 μg was associated with a significantly greater FFR compared to the intravenous infusion (0.02 ± 0.03, p = 0.001). The intracoronary doses of 300 (-0.01 ± 0.00; p = 0.006) and 600 μg (-0.02 ± 0.00; p <0.0005) were significantly associated with a smaller FFR compared to the intravenous infusion. An intracoronary dose of 600 μg revealed a significantly greater percentage of lesions with an FFR <0.80 compared to intravenous infusion at 140 μg/kg/min (37.6 vs 31.5%; p <0.05) and 200 μg/kg/min (37.6 vs 32.4%; p <0.05) and compared to intracoronary doses of 60 (26.9%) and 180 μg (31.5%). In conclusion, an intracoronary bolus dose >300 μg can be equal to or more effective than an intravenous infusion of adenosine in achieving maximum hyperemia when calculating the FFR. Its use could simplify these procedures without having an effect on safety.