Effective radiation dose, time, and contrast medium to measure fractional flow reserve

A high-fidelity geometric multiscale hemodynamic model for predicting myocardial ischemia

BACKGROUND AND OBJECTIVES

Coronary computed tomography angiography (CCTA) derived fractional flow reserve (CT-FFR) requires a maximal hyperemic state to be modeled by assuming the total coronary resistance decreased to a constant 0.24 of that under the resting state. However, this assumption neglects the vasodilator capacity of individual patients. Herein, we proposed a high-fidelity geometric multiscale model (HFMM) to characterize coronary pressure and flow under the resting state, seeking to better predict myocardial ischemia by using CCTA-derived instantaneous wave-free ratio (CT-iFR).

METHODS

Fifty-seven patients (62 lesions) who had undergone CCTA and were then referred to invasive FFR were prospectively enrolled. The coronary microcirculation resistance hemodynamic model (RHM) under the resting condition was established on a patient-specific basis. Coupled with a closed-loop geometric multiscale model (CGM) of their individual coronary circulations, the HFMM model was established to non-invasively derive the CT-iFR from CCTA images.

RESULTS

With the invasive FFR being the reference standard, accuracy of the obtained CT-iFR in identifying myocardial ischemia was greater than those of the CCTA and non-invasively derived CT-FFR (90.32% vs. 79.03% vs. 84.3%). The overall computational time of CT-iFR was 61 ± 6 min, faster than that of the CT-FFR (8 h). The sensitivity, specificity, positive predictive value, and negative predictive value of the CT-iFR in discriminating an invasive FFR > 0.8 were 78% (95% CI: 40-97%), 92% (95% CI: 82-98%), 64% (95% CI: 39-83%), and 96% (95% CI:88-99%), respectively.

CONCLUSIONS

A high-fidelity geometric multiscale hemodynamic model was developed for rapid and accurate estimation of CT-iFR. Compared with CT-FFR, CT-iFR is of less computational cost and enables assessment of tandem lesions.

Exercise-induced change in circulating NT-proBNP could not distinguish between patients with and without coronary artery disease: the CADENCE study

Objective. In patients with chest pain, exercise stress test has a moderate accuracy for coronary artery disease (CAD). Adding a reliable cardiac biomarker to the exercise test could potentially improve the precision of the test. We investigated circulating NT-proBNP levels before and during exercise stress test in patients with and without angiographically verified CAD. We hypothesized that NT-proBNP would give an additive diagnostic value to the exercise stress test. Methods. In patients presenting with symptoms of stable CAD, venous blood samples were taken at rest and within 5 min of termination of a maximal stress test on a bicycle ergometer. All study participants underwent coronary angiography. Significant CAD was defined as ≥75% stenosis in one or more segments of the coronary arteries. Results. Of the 297 participants, significant CAD was found in 111 (37%) patients. Resting levels of NT-proBNP were significantly higher in patients with CAD compared with patients without CAD (74.18 vs. 56.03 ng/L), p = .005. During exercise, NT-proBNP levels increased in the total population (p < .001). The rise was, however, not significantly different between the two groups (8.24 vs. 8.51 ng/L), p = .700. Combining resting NT-proBNP with positive exercise stress test was superior to exercise test alone in predicting CAD, AUC = 0.68 vs. 0.64. Conclusion. Exercise-induced change in circulating NT-proBNP could not distinguish between patients with or without CAD. However, resting levels of NT-proBNP were significantly higher in patients with CAD than those without CAD.

Impact of machine-learning-based coronary computed tomography angiography-derived fractional flow reserve on decision-making in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement

OBJECTIVES

To evaluate feasibility and diagnostic performance of coronary CT angiography (CCTA)-derived fractional flow reserve (CT-FFR) for detection of significant coronary artery disease (CAD) and decision-making in patients with severe aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR) to potentially avoid additional pre-TAVR invasive coronary angiography (ICA).

METHODS

Consecutive patients with severe AS (n = 95, 78.6 ± 8.8 years, 53% female) undergoing pre-procedural TAVR-CT followed by ICA with quantitative coronary angiography were retrospectively analyzed. CCTA datasets were evaluated using CAD Reporting and Data System (CAD-RADS) classification. CT-FFR measurements were computed using an on-site machine-learning algorithm. A combined algorithm was developed for decision-making to determine if ICA is needed based on pre-TAVR CCTA: [1] all patients with CAD-RADS ≥ 4 are referred for ICA; [2] patients with CAD-RADS 2 and 3 are evaluated utilizing CT-FFR and sent to ICA if CT-FFR ≤ 0.80; [3] patients with CAD-RADS < 2 or CAD-RADS 2-3 and normal CT-FFR are not referred for ICA.

RESULTS

Twelve patients (13%) had significant CAD (≥ 70% stenosis) on ICA and were treated with PCI. Twenty-eight patients (30%) showed CT-FFR ≤ 0.80 and 24 (86%) of those were reported to have a maximum stenosis ≥ 50% during ICA. Using the proposed algorithm, significant CAD could be identified with a sensitivity, specificity, and positive and negative predictive value of 100%, 78%, 40%, and 100%, respectively, potentially decreasing the number of necessary ICAs by 65 (68%).

CONCLUSION

Combination of CT-FFR and CAD-RADS is able to identify significant CAD pre-TAVR and bears potential to significantly reduce the number of needed ICAs.

KEY POINTS

• Coronary CT angiography-derived fractional flow reserve (CT-FFR) using machine learning together with the CAD Reporting and Data System (CAD-RADS) classification safely identifies significant coronary artery disease based on quantitative coronary angiography in patients prior to transcatheter aortic valve replacement. • The combination of CT-FFR and CAD-RADS enables decision-making and bears the potential to significantly reduce the number of needed invasive coronary angiographies.

INCREASED EXPOSURE TO X-RAYS DURING CORONARY ANGIOGRAPHY AND PERCUTANEOUS CORONARY INTERVENTIONS ASSOCIATED WITH FRACTIONAL FLOW RESERVE MEASUREMENT AND ENDOCORONARY IMAGING TECHNIQUES

Growing use of fractional flow reserve (FFR) and intracoronary imaging techniques by optical coherence tomography or intravascular ultrasound has raised concerns about additional exposure during coronary angiography and percutaneous coronary interventions (PCIs). Using data from the prospective CRAC-France PCI Prospective Multicentre registry, we sought to evaluate the effect of these new techniques on the radiation dose to patients undergoing coronary procedures. Data on Kerma Area Product (PKA), total air kerma (KAr) and fluoroscopy time from 42 182 coronary procedures were retrospectively compared, using multivariable linear regression, according to whether they included FFR and intracoronary imaging. In coronary angiography, FFR was associated with longer fluoroscopy time and higher PKA (21.0 vs. 18.9 Gy.cm2) and KAr (372 vs. 299 mGy) (all p < 0.001). Intracoronary imaging was associated with longer fluoroscopy time, higher contrast volume (both p < 0.001), lower PKA (18.3 vs. 19.0 Gy.cm2, p = 0.02) and similar KAr. In PCI, FFR was associated with a moderate increase in KAr (682 vs. 626 mGy, p < 0.01) but not PKA (35.9 vs. 33.7 Gy.cm2, p = 0.34). For intracoronary imaging, there were no differences between groups, except for contrast volume. Increased patient exposure associated with FFR and intracoronary imaging is moderate in diagnostic coronary angiography and minimal or none in PCI, provided optimization techniques are used. It should not be a limitation on the use of these techniques given the important additional information they provide.

Meta-Analysis of Complete versus Culprit-Only Revascularization in Patients with ST-Segment Elevation Myocardial Infarction and Multivessel Coronary Disease

Approximately half of patients with ST-segment elevation myocardial infarction (STEMI) present with noninfarct related multivessel coronary artery disease (CAD) during primary percutaneous coronary intervention (PCI). However, questions remain concerning whether patients with STEMI and multivessel CAD should routinely undergo complete revascularization. Our objective was to compare the risks of major cardiovascular outcomes and procedural complications in patients with STEMI and multivessel CAD randomized to complete revascularization versus culprit-only PCI. We conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) comparing complete revascularization to culprit-only PCI. RCTs were identified via a systematic search of MEDLINE, Embase, and Cochrane CENTRAL. Count data were pooled using DerSimonian and Laird random-effects models with inverse variance weighting to obtain relative risks (RRs) and 95% confidence intervals (CIs). A total of 9 RCTs (n = 6,751) were included, with mean/median follow-up times ranging from 6 to 36 months. Compared with culprit-only PCI, complete revascularization was associated with a substantial reduction in major adverse cardiovascular events (13.1% vs 22.1%; RR: 0.54; 95%CI: 0.43 to 0.66), repeat myocardial infarction (4.9% vs 6.8%; RR: 0.64; 95%CI: 0.48 to 0.84), and repeat revascularization (3.7% vs 12.3%; RR: 0.33; 95%CI: 0.25 to 0.44). Complete revascularization may have beneficial effects on all-cause and cardiovascular mortality, but 95%CIs were wide. Findings for stroke, major bleeding, and contrast-induced acute kidney injury were inconclusive. In conclusion, complete coronary artery revascularization appears to confer benefit over culprit-only PCI in patients with STEMI and multivessel CAD, and should be considered a first-line strategy in these patients.

Patient Body Mass Index and Occupational Radiation Doses to Circulating Nurses During Coronary Angiography

BACKGROUND

Patient BMI is associated with radiation doses received by interventional cardiologists, yet the association between patient BMI and nurse radiation doses is unknown. This study evaluated the association between patient body mass index (BMI) and nurse radiation doses during coronary angiography.

METHODS

Nurse radiation doses were collected by real-time dosimeters during consecutive coronary angiography procedures and are reported as the personal dose equivalent (H_p10). Patient radiation doses were estimated using dose area product (DAP). Patient BMI was categorized in kg/m² as <25.0, 25.0-29.9, 30.0-34.9, 35.0-39.9, and ≥40. Multiple regression analysis determined procedural factors independently association with nurse radiation doses.

RESULTS

In 643 consecutive coronary angiography procedures, patient radiation doses increased significantly across increasing patient BMI categories (p < 0.001). Compared to a patient BMI <25, a patient BMI ≥40 was associated with a 2.3-fold increase in DAP (p < 0.001). Significant differences were also observed in nurse radiation doses across patient BMI categories (p = 0.036). Compared to a patient BMI <25, a patient BMI ≥40 was associated with a 4.0-fold increase in nurse radiation dose (BMI < 25: 0.3 [0.1, 1.3] μSv; BMI ≥ 40: 1.2 [0.2, 2.9] μSv; p = 0.003). By multiple regression analysis, each 1-unit kg/m² increase in patient BMI was associated with a 3.3% increase in nurse radiation dose (p = 0.002).

CONCLUSIONS

Patient BMI was significantly associated with nurse radiation doses during coronary angiography. These observations may have important implications on nurse radiation safety, especially in the setting of the ongoing obesity epidemic.

The Effect of Functional and Intra-Coronary Imaging Techniques on Fluoroscopy Time, Radiation Dose and Contrast Volume during Coronary Angiography

The aim was to analyze the effect of fractional flow reserve (FFR), intravascular ultrasound (IVUS) and optical coherence tomography (OCT) on fluoroscopy time (FT), radiation dose (RD) and contrast volume (CV) in patients undergoing coronary angiography. This case-control study included consecutive patients above the age of 18, who underwent coronary angiography. FT, RD, and CV after each procedure were retrospectively recorded. Multivariate models were used to demonstrate the effect of these complementary studies and other factors, on radiation and contrast exposure. A total of 1047 patients were included, 74.5% were men and the mean (SD) age was 62.4 (12.1) years. Complementary studies performed were: IVUS (n = 237), FFR (n = 56) and OCT (n = 37). FFR and IVUS had a small effect on FT (η = 0.008 B = 2.2, p < 0.001; η = 0.009, B = 2.5, p < 0.001), while OCT had no effect (η = 0.002 B = 2.9, p < 0.183). IVUS, FFR and OCT had no effect on the RD. IVUS did not affect contrast volume (η = 0.002 B = 9.4, p < 0.163) while OCT and FFR had a small effect on CV (η = 0.006 B = 39, p < 0.01; η = 0.008 B = 37, p < 0.003). The number of placed stents had a significant effect on FT (η = 0.192, Β = 4.2, p < 0.001), RD (η = 0.129, Β = 511.8, p < 0.001) and CV (η = 0.177, Β = 40.5, p < 0.001). The use of complementary studies in hemodynamics did not modify the received RD and had a minor effect on FT and the CV used.

Angiogram based fractional flow reserve in patients with dual/triple vessel coronary artery disease

OBJECTIVE

To assess the performance of angiography derived Fractional Flow Reserve (FFRangio) in multivessel disease (MVD) patients undergoing angiography.

BACKGROUND

FFR is the reference standard for physiologic assessment of coronary stenosis and guidance of revascularization, especially in patients with MVD, yet it remains grossly underutilized. The non-wire based FFRangio performs well in non-MVD patients, but its accuracy in MVD is unknown.

METHODS

A prospective clinical study was conducted at Gifu Heart Centre, Japan. Patients underwent physiologic assessment of all relevant coronary lesions using wire-based FFR (wbFFR) and FFRangio. Primary outcome was diagnostic performance (sensitivity, specificity, accuracy) for FFRangio with wbFFR as reference. Other outcomes were the correlation between wbFFR/FFRangio, time required for wbFFR/FFRangio measurements, and the effect of wbFFR/FFRangio on the reclassification of coronary disease severity.

RESULTS

Fifty patients (118 lesions in total) were included. Mean age was 72 ± 9 years, 72% were male, 36% had triple vessel disease and the average SYNTAX score was 13. The mean measurement of wbFFR and FFRangio were 0.83 ± 0.12 and 0.81 ± 0.11, respectively. Accuracy, sensitivity and specificity for FFRangio were 92.3% (95% CI 79.1-98.4%), 92.4% (95% CI 84.3-97.2%) and 92.4% (95% CI 87.4-97.3%), respectively. Pearson's r between wbFFR and FFRangio was 0.83. FFRangio measurement was faster than wbFFR (9.6 ± 3.4 vs. 15.0 ± 8.9 min, p < 0.001).

CONCLUSIONS

In patients with MVD, FFRangio shows good correlation and excellent diagnostic performance compared to wbFFR, and measuring FFRangio is faster than wbFFR. These results highlight the potential clinical benefits of utilizing FFRangio among patients with MVD.

Prognostic Value of Preserved Coronary Flow Velocity Reserve by Noninvasive Transthoracic Doppler Echocardiography in Patients With Angiographically Intermediate Left Main Stenosis

BACKGROUND

The potential of angiography to evaluate the hemodynamic severity of a left main coronary artery (LM) stenosis is limited. Noninvasive transthoracic Doppler echocardiographic coronary flow velocity reserve (CFVR) evaluation of intermediate coronary stenosis has demonstrated remarkably high negative prognostic value. The aim of this study was to assess clinical outcomes in patients with angiographically intermediate LM stenosis and preserved CFVR (>2.0) as evaluated by transthoracic Doppler echocardiographic CFVR.

METHODS

The initial study population included 102 patients with intermediate coronary stenosis of the LM referred for transthoracic Doppler echocardiographic CFVR assessment. Peak diastolic CFVR measurements were performed in the distal segment of the left anterior descending coronary artery after intravenous adenosine (140 μg/kg/min), and CFVR was calculated as the ratio between maximal hyperemic and baseline coronary flow velocity. Nineteen patients had impaired CFVR (≤2.0) and were excluded from further analysis, as well as two patients with poor acoustic windows. The final group consisted of 81 patients (mean age, 60 ± 9 years; 76 men) evaluated for adverse cardiac events including death, myocardial infarction, and revascularization.

RESULTS

Mean follow-up duration was 62 ± 26 months. Mean CFVR was 2.4 ± 0.4. Total event-free survival was 75 of 81 (92.6%), as six patients were referred for revascularization (five patients with coronary artery bypass grafting, one patient with percutaneous coronary intervention). There were no documented myocardial infarctions or cardiovascular deaths in the follow-up period.

CONCLUSIONS

In patients with angiographically intermediate and equivocal LM stenosis and preserved CFVR values of >2.0, revascularization can be safely deferred.

Fractional flow reserve (FFR) as a guide to treat coronary artery disease

INTRODUCTION

The presence and extent of myocardial ischemia are the major determinants of prognosis in patients with coronary artery disease (CAD). Unlike coronary angiography alone, fractional flow reserve (FFR) has enabled interventional cardiologists to accurately determine whether coronary atherosclerotic plaques are responsible for myocardial ischemia, and therefore deserve to be revascularized. Areas covered: An overview on the role of FFR in the diagnosis and treatment of coronary artery disease, as well as the potential related controversies is provided. Authors describe the coronary physiology underneath this technique and all the procedural aspects in the catheterization laboratory. The landmark trials and the current applications in different coronary lesions and syndromes are also described and potential future research involving FFR and comparisons with other methodologies for the evaluation of coronary physiology are introduced. Expert commentary: FFR is still unsurpassed in diagnostic performance when compared to non-hyperemic indices and noninvasive techniques, and remains the gold standard for the detection of ischemia-inducing coronary stenoses. FFR-guided PCI has been demonstrated superior to an angiography-guided PCI and over medical therapy alone, and ongoing investigation will clarify whether it could perform better, or at least equalize the results of cardiac surgery in patients with severe multivessel disease.

Feasibility of coronary fractional flow reserve with dual anti-platelet therapy in low risk coronary lesions without systemic anticoagulation-results of the SMART-FFR study

BACKGROUND

Fractional flow reserve (FFR) is used to assess the functional significance of coronary artery stenoses. The optimal anti-thrombotic regimen for FFR has not been studied.

PURPOSE

The goal of this study was to determine whether FFR could be safely performed in Type A coronary lesions, using only upstream dual anti-platelet therapy (DAT) with aspirin and clopidogrel, compared with DAT plus anticoagulation in low risk coronary lesions.

METHODS/MATERIALS

Two hundred patients undergoing FFR for Type A intermediate coronary lesions were blindly randomized into two groups of 100 patients each. Group 1: Upstream DAT, without intra-procedural anti-coagulation and Group 2: Upstream DAT plus intra-procedural bivalirudin. The primary end-points were any coronary thrombotic complications during the index hospital stay, and a composite end-point of any major adverse cardiovascular events (MACE) at 30-days. Secondary end-points included post-procedure troponin levels and TIMI major and minor bleeding scores.

RESULTS

There were no thrombotic complications reported. At 30-days, two MACE occurred in Group 1, and three in Group 2 (p=0.83). No difference was seen in the post-procedure troponin levels (p=0.72), or TIMI bleeding scores study between groups (p=093).

CONCLUSIONS

This initial study evaluating a simplified anti-thrombotic regimen for FFR, suggests that FFR can be performed in low risk coronary lesions using DAT without the need for intra-procedural anticoagulation, with similar results as DAT plus anticoagulation with bivalirudin. Further research in this area is needed to determine the optimal and most cost-effective anti-thrombotic regimen for FFR calculation.

Validation Study of Image-Based Fractional Flow Reserve During Coronary Angiography

Background—

Fractional flow reserve (FFR), an index of the hemodynamic severity of coronary stenoses, is derived from invasive measurements and requires a pressure-monitoring guidewire and hyperemic stimulus. Angiography-derived FFR measurements (FFR angio ) may have several advantages. The aim of this study is to assess the diagnostic performance and interobserver reproducibility of FFR angio in patients with stable coronary artery disease.

Methods and Results—

FFR angio is a computational method based on rapid flow analysis for the assessment of FFR. FFR angio uses the patient’s hemodynamic data and routine angiograms to generate a complete 3-dimensional coronary tree with color-coded FFR values at any epicardial location. Hyperemic flow ratio is derived from an automatic resistance-based lumped model of the entire coronary tree. A total of 203 lesions were analyzed in 184 patients from 4 centers. Values derived using FFR angio ranged from 0.5 to 0.97 (median 0.85) and correlated closely (Spearman ρ=0.90; P <0.001) with the invasive FFR measurements, which ranged from 0.5 to 1 (median 0.84). In Bland–Altman analyses, the 95% limits of agreement between these methods ranged from −0.096 to 0.112. Using an FFR cutoff value of 0.80, the sensitivity, specificity, and diagnostic accuracy of FFR angio were 88%, 95%, and 93%, respectively. The intraclass coefficient between 2 blinded operators was 0.962 with a 95% confidence interval from 0.950 to 0.971, P <0.001.

Conclusions—

There is a high concordance between FFR angio and invasive FFR. The color-coded display of FFR values during coronary angiography facilitates the integration of physiology and anatomy for decision making on revascularization in patients with stable coronary artery disease.

Clinical Trial Registration—

URL: https://www.clinicaltrials.gov . Unique identifier: NCT03005028.

Case Report of First Angiography-Based On-Line FFR Assessment during Coronary Catheterization

Fractional flow reserve (FFR), an index of the hemodynamic severity of coronary stenoses, is derived from hyperemic pressure measurements and requires a pressure-monitoring guide wire and hyperemic stimulus. Although it has become the standard of reference for decision-making regarding coronary revascularization, the procedure remains underutilized due to its invasive nature. FFR_angio is a novel technology that uses the patient's hemodynamic data and routine angiograms to generate a complete three-dimensional coronary tree, with color-coded display of the FFR values at each point along the vessels. After being proven to be as accurate as invasive FFR measurements in an off-line study, this case report presents the first on-line application of the system in the catheterization lab. Here too, a high concordance between FFR_angio and invasive FFR was observed. In light of the demonstrated capabilities of the FFR_angio system, it should emerge as an important tool for clinical decision-making regarding revascularization in patients with coronary artery disease.

Pooled comparison of regadenoson versus adenosine for measuring fractional flow reserve and coronary flow in the catheterization laboratory

BACKGROUND

Adenosine is the gold standard for augmenting coronary flow during fractional flow reserve (FFR) testing of intermediate coronary stenoses. However, intravenous infusion is time-consuming and intracoronary injection is subject to variability. Regadenoson is a newer adenosine alternative administered as a single intravenous bolus during nuclear stress testing, but its efficacy and safety during FFR testing have been evaluated only in small, single-center studies.

METHODS

We pooled data from 5 academic hospitals, in which patients undergoing clinically-indicated FFR prospectively underwent comparison of intravenous adenosine infusion (140-175mcg/kg/min) versus regadenoson bolus (400mcg). Hemodynamics and symptoms with adenosine were recorded until maximal hyperemia occurred, and after returning to baseline hemodynamics, regadenoson was administered and monitoring was repeated. In a subset of patients with coronary flow data, average peak velocity (APV) at the distal flow sensor was recorded.

RESULTS

Of 149 patients enrolled, mean age was 59±9years, 76% were male, and 54% underwent testing of the left anterior descending artery. Mean adenosine-FFR and regadenoson-FFR were identical (0.82±0.10) with excellent correlation of individual values (r=0.96, p<0.001) and no difference in patient-reported symptoms. Four patients (2.6%) had discrepancies between the 2 drugs for the clinical decision-making cutoff of FFR≤0.80. Coronary flow responses to adenosine and regadenoson were similar (APV at maximal hyperemia 36cm/s for both, p=0.81).

CONCLUSIONS

Regadenoson single-bolus administration has comparable FFR, symptoms, and coronary flow augmentation when compared with standard intravenous adenosine infusion. With its greater ease of administration, regadenoson may be a more "user-friendly" option for invasive ischemic testing.

Invasive evaluation of patients with angina in the absence of obstructive coronary artery disease

BACKGROUND

More than 20% of patients presenting to the cardiac catheterization laboratory with angina have no angiographic evidence of coronary artery disease. Despite a "normal" angiogram, these patients often have persistent symptoms, recurrent hospitalizations, a poor functional status, and adverse cardiovascular outcomes, without a clear diagnosis.

METHODS AND RESULTS

In 139 patients with angina in the absence of obstructive coronary artery disease (no diameter stenosis >50%), endothelial function was assessed; the index of microcirculatory resistance, coronary flow reserve, and fractional flow reserve were measured; and intravascular ultrasound was performed. There were no complications. The average age was 54.0±11.4 years, and 107 (77%) were women. All patients had at least some evidence of atherosclerosis based on an intravascular ultrasound examination of the left anterior descending artery. Endothelial dysfunction (a decrease in luminal diameter of >20% after intracoronary acetylcholine) was present in 61 patients (44%). Microvascular impairment (an index of microcirculatory resistance ≥25) was present in 29 patients (21%). Seven patients (5%) had a fractional flow reserve ≤0.80. A myocardial bridge was present in 70 patients (58%). Overall, only 32 patients (23%) had no coronary explanation for their angina, with normal endothelial function, normal coronary physiological assessment, and no myocardial bridging.

CONCLUSIONS

The majority of patients with angina in the absence of obstructive coronary artery disease have occult coronary abnormalities. A comprehensive invasive assessment of these patients at the time of coronary angiography can be performed safely and provides important diagnostic information that may affect treatment and outcomes.

Current Status of Coronary Intervention in Patients with ST-Segment Elevation Myocardial Infarction and Multivessel Coronary Artery Disease

Primary percutaneous coronary intervention (PCI) is a standard interventional treatment modality for ST-segment elevation myocardial infarction (STEMI). Diagnostic coronary angiogram during PCI reveals multivessel coronary artery disease in about half of patients with STEMI, and it is difficult to make decision on the extent of intervention in these patients. Although revascularization for the infarct-related artery only is still effective for STEMI patients, several studies have reported the efficacy of multivessel revascularization during primary PCI, as well as in a staged PCI procedure. Clinicians should consider clinical aspects such as initial cardiogenic shock and myocardial viability when performing primary multivessel intervention, including the risks and benefits of multivessel revascularization in patients undergoing primary PCI. This review describes the current status of performing multivessel PCI in patients with STEMI and proposes an optimal revascularization strategy based on the previous literature.

Improvement in coronary haemodynamics after percutaneous coronary intervention: assessment using instantaneous wave-free ratio

Objective

To determine whether the instantaneous wave-free ratio (iFR) can detect improvement in stenosis significance after percutaneous coronary intervention (PCI) and compare this with fractional flow reserve (FFR) and whole cycle Pd/Pa.

Design

A prospective observational study was undertaken in elective patients scheduled for PCI with FFR ≤0.80. Intracoronary pressures were measured at rest and during adenosine-mediated vasodilatation, before and after PCI. iFR, Pd/Pa and FFR values were calculated using the validated fully automated algorithms.

Setting

Coronary catheter laboratories in two UK centres and one in the USA.

Patients

120 coronary stenoses in 112 patients were assessed. The mean age was 63±10 years, while 84% were male; 39% smokers; 33% with diabetes. Mean diameter stenosis was 68±16% by quantitative coronary angiography.

Results

Pre-PCI, mean FFR was 0.66±0.14, mean iFR was 0.75±0.21 and mean Pd/Pa 0.83±0.16. PCI increased all indices significantly (FFR 0.89±0.07, p<0.001; iFR 0.94±0.05, p<0.001; Pd/Pa 0.96±0.04, p<0.001). The change in iFR after intervention (0.20±0.21) was similar to ΔFFR 0.22±0.15 (p=0.25). ΔFFR and ΔiFR were significantly larger than resting ΔPd/Pa (0.13±0.16, both p<0.001). Similar incremental changes occurred in patients with a higher prevalence of risk factors for microcirculatory disease such as diabetes and hypertension.

Conclusions

iFR and FFR detect the changes in coronary haemodynamics elicited by PCI. FFR and iFR have a significantly larger dynamic range than resting Pd/Pa. iFR might be used to objectively document improvement in coronary haemodynamics following PCI in a similar manner to FFR.

Noninvasive fractional flow reserve derived from coronary computed tomography angiography: integrated anatomical and functional assessment

Coronary computed tomographic angiography (CCTA) provides anatomic detail of lumen stenosis and information on plaque burden, plaque extent and plaque characteristics. CCTA does not, however, provide insight into the hemodynamic significance of a stenosis, which is essential to allow appropriate revascularization decision-making. This could reduce downstream invasive coronary angiography and nonbeneficial coronary revascularization, particularly with intermediate coronary stenosis. Invasive fractional flow reserve (FFR) is the gold standard for the determination of lesion-specific ischemia and the need for revascularization. Advances in computational technology now permit calculation of FFR using resting CCTA image data, without the need for additional radiation or medication. Early data demonstrate improved accuracy and a discriminatory ability of FFR computed tomography to identify ischemia-producing lesions compared with CCTA alone. This new, combined anatomic-functional assessment has the potential to simplify the noninvasive diagnosis of coronary artery disease with a single study to identify patients with ischemia-causing stenosis who may benefit from revascularization.

Hybrid iFR-FFR decision-making strategy: implications for enhancing universal adoption of physiology-guided coronary revascularisation

AIMS

Adoption of fractional flow reserve (FFR) remains low (6-8%), partly because of the time, cost and potential inconvenience associated with vasodilator administration. The instantaneous wave-Free Ratio (iFR) is a pressure-only index of stenosis severity calculated without vasodilator drugs. Before outcome trials test iFR as a sole guide to revascularisation, we evaluate the merits of a hybrid iFR-FFR decision-making strategy for universal physiological assessment.

METHODS AND RESULTS

Coronary pressure traces from 577 stenoses were analysed. iFR was calculated as the ratio between Pd and Pa in the resting diastolic wave-free window. A hybrid iFR-FFR strategy was evaluated, by allowing iFR to defer some stenoses (where negative predictive value is high) and treat others (where positive predictive value is high), with adenosine being given only to patients with iFR in between those values. For the most recent fixed FFR cut-off (0.8), an iFR of <0.86 could be used to confirm treatment (PPV of 92%), whilst an iFR value of >0.93 could be used to defer revascularisation (NPV of 91%). Limiting vasodilator drugs to cases with iFR values between 0.86 to 0.93 would obviate the need for vasodilator drugs in 57% of patients, whilst maintaining 95% agreement with an FFR-only strategy. If the 0.75-0.8 FFR grey zone is accounted for, vasodilator drug requirement would decrease by 76%.

CONCLUSION

A hybrid iFR-FFR decision-making strategy for revascularisation could increase adoption of physiology-guided PCI, by more than halving the need for vasodilator administration, whilst maintaining high classification agreement with an FFR-only strategy.

Use of regadenoson for measurement of fractional flow reserve

OBJECTIVE

To compare the use of regadenoson to adenosine for measurement of fractional flow reserve (FFR).

BACKGROUND

FFR is an accepted method to assess the functional significance of intermediate coronary artery stenoses and uses adenosine to induce maximal hyperemia. The use of the selective A2a receptor agonist regadenoson for FFR is not established.

METHODS

Fifty-seven patients undergoing clinically indicated FFR assessment of intermediate coronary stenoses were included. For the initial assessment of FFR, hyperemia was achieved by a standard intravenous adenosine infusion (140 mcg/kg/min). After a washout period of 10 min, FFR was reassessed using regadenoson as a single 0.4 mg intravenous bolus. FFR measurements were recorded at baseline and following maximal hyperemia with both agents.

RESULTS

Mean age was 57 ± 8 years and 47 were male. Sixty coronary lesions were evaluated and were located in the left anterior descending in 34, the left circumflex in 9, right coronary in 15, and left main coronary artery in 2. Mean ( ± SD) FFR following adenosine and regadenoson was 0.79 ( ± 0.09) and 0.79 (±0.09), respectively, P = NS. Time to FFR nadir was shorter with regadenoson compared to adenosine, 36.6 ± 24 versus 66 ± 0.19 sec, P < 0.0001, respectively. No patients experienced any significant side effects related to regadenoson.

CONCLUSIONS

Regadenoson is a viable alternative to intravenous adenosine for achieving maximal hyperemia during FFR assessment. Compared to adenosine, regadenoson has a similar hemodynamic response, achieves more rapid hyperemia, is easier to use, and has an excellent side-effect profile.

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.

Coronary physiology in the cath lab: beyond the basics

The adoption of invasive coronary physiologic lesion assessment before percutaneous coronary intervention has become routine in many catheterization laboratories. In the last decade, numerous studies have demonstrated favorable outcomes for revascularization decisions based on in-lab coronary physiology in many patients. The use of coronary physiology in the laboratory has been identified as a class IIa recommendation for patients in whom the clinical presentation and supporting data are too inconclusive to make an objective decision regarding treatment. This article reviews pertinent concepts and studies of the more complex applications of translesional pressure measurements for optimal patient outcomes.