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

Diagnostic Performance of Diastolic Hyperemia-Free Ratio Compared With Invasive Fractional Flow Reserve for Evaluation of Coronary Artery Disease

Hyperemic and nonhyperemic pressure ratios are frequently used to assess the hemodynamic significance of coronary artery disease and to guide the need for myocardial revascularization. However, there are limited data on the diagnostic performance of the diastolic hyperemia-free ratio (DFR). We evaluated the diagnostic performance of the DFR compared with invasive fractional flow reserve (FFR). We performed a prospective, single-center study of 308 patients (343 lesions) who underwent DFR and FFR for evaluation of visually estimated 40% to 90% stenoses. Diagnostic performance of the DFR compared with FFR was evaluated using linear regression, Bland-Altman analysis, and receiver operating characteristic curves. The overall diagnostic accuracy of the DFR was 83%; the accuracy rates were 86%, 40%, and 95% when the DFR was <0.86, 0.88 to 0.90, and >0.93, respectively. The sensitivity, specificity, positive predicative value, and negative predictive value were 60%, 91%, 71%, and 87%, respectively. The Pearson correlation coefficient was 0.75 (p <0.05). The Bland-Altman analysis showed a mean difference of 0.09, and the area under the receiver operating characteristic curve was 0.88 (95% confidence interval 0.84 to 0.92, p <0.05). In conclusion, the DFR has a good diagnostic performance compared with FFR but 17% of the measurements were discordant. The diagnostic accuracy of the DFR was only 40% when the DFR was 0.88 to 0.90, suggesting that FFR may be useful in these arteries.

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

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

The influence of flow distribution strategy for the quantification of pressure- and wall shear stress-derived parameters in the coronary artery: A CTA-based computational fluid dynamics analysis

For image-based computational fluid dynamics (CFD) analysis to characterize the local coronary hemodynamic environment, the accuracy depends on the flow rate which is in turn associated with outlet branches' morphology. A good flow distribution strategy is important to mitigate the effect when certain branches cannot be considered. In this study, stenotic coronary arteries from 13 patients were used to analyze the effect of missing branches and different flow distribution strategies. Pressure- and wall shear stress (WSS)-derived parameters around the stenotic region (ROI) were compared, including fractional flow reserve (CT-FFR), instantaneous wave-free ratio (CT-iFR), resting distal to aortic coronary pressure (CT-Pd/Pa), time-averaged WSS, oscillatory shear index (OSI) and relative residence time (RRT). Three flow distribution strategies were the Huo-Kassab model at distal outlets (Type I), flow distribution based on outlet resistances (Type II), and a developed algorithm distributing flow at each bifurcation until the final outlets (Type III). Results showed that Type III strategy for models with truncated branch(es) had a good agreement in both pressure- and WSS-related results (interquatile range less than 0.12% and 4.02%, respectively) with the baseline model around the ROI. The relative difference of pressure- and WSS-related results were correlated with the flow differences in the ROI to the baseline mode. Type III strategy had the best performance in maintaining the flow in intermediate branches. It is recommended for CFD analysis. Removal of branches distal to a stenosis can be undertaken with an improved performance and maintained accuracy, while those proximal to the ROI should be kept.

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

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

Diagnostic performance of corrected FFRCT metrics to predict hemodynamically significant coronary artery stenosis

OBJECTIVES

To determine the diagnostic performance of the fractional flow reserve (FFR) derived from coronary computed tomography angiography (CCTA) (FFR_CT) difference across the lesion (ΔFFR_{CT lesion}) or the vessel (ΔFFR_{CT vessel}) and the gradient of FFR_CT for the identification of hemodynamically significant coronary stenosis.

METHODS

From June 2016 to December 2018, 73 patients suspected of having coronary artery disease who underwent CCTA followed invasive coronary angiography (ICA) within 1 month were retrospectively included. ΔFFR_{CT lesion}, ΔFFR_{CT vessel}, and FFR_CT gradient were calculated. Performance characteristics of different corrected FFR_CT metrics in detecting ischemic stenosis were analyzed. Impacts of coronary calcification and lesion length on the corrected FFR_CT metrics were also analyzed.

RESULTS

The diagnostic sensitivities, specificities, and accuracies of 94.4%, 88.7%, and 91.0% with ΔFFR_{CT lesion}, 57.1%, 72.3%, and 65.2% with ΔFFR_{CT vessel}, and 50.0%, 85.1%, and 68.5% with FFR_CT gradient, respectively, were detected. There was higher specificity, accuracy, and area under the curve (AUC) for ΔFFR_{CT lesion} compared with CCTA (p < 0.05 for all). The specificity and AUC of FFR_CT gradient and ΔFFR_{CT vessel} were significantly higher than CCTA (p < 0.05 for all). Coronary calcification showed no impact on corrected FFR_CT metrics. ΔFFR_{CT lesion} for lesion length ratio (LLR) < 1/10 was significantly lower than that for LLR 1/10 to 3/10 and LLR > 3/10.

CONCLUSIONS

ΔFFR_{CT lesion} was significantly correlated with the hemodynamically significant coronary artery stenosis. ΔFFR_{CT lesion} had the potential to be immediately used in real-world practice to discriminate ischemic coronary artery stenosis.

KEY POINTS

• The difference of FFR_CT across the lesion or the vessel and the gradient of FFR_CT was related to the hemodynamically significant coronary artery stenosis. • The difference of FFR_CT across the lesion showed the best diagnostic performance in detecting the hemodynamically significant coronary artery stenosis. • Coronary calcification showed no impact on corrected FFR_CT metrics, while lesion length related to the difference of FFR_CT across the lesion.

Assessing the Accuracy of a second-generation optical sensor pressor wire in a wire to wire comparison (The ACCURACY study)

BACKGROUND

The phenomenon of "pressure drift" increases uncertainty about the correct FFR value. Redesigned and incorporating an optical pressure sensor, the "OptoWire Deux™" is purported to be less prone to the pressure drift seen with piezoelectric coronary pressure wires. The aim of this first in vivo real-world clinical study is to evaluate the performance of OptoWire Deux™ in terms of measurements agreement and propensity to pressure drift in a wire to wire comparison.

METHODS

This is a single center, prospective, non-blinded clinical investigation enrolling 45 consecutive patients with a clinical indication for coronary lesion FFR assessment. Lesions were either simultaneously assessed with two optical sensor pressure wires (OSPW) (Group O-O; 30 patients, 34 lesions) or one OSPW and one piezoelectric pressure wire (PEPW) simultaneously (Group O-P; 15 patients, 15 lesions). Significant drift was defined as a pressure ratio deviation of >0.03.

RESULTS

Mean FFR measurements in Group OO were not statistically different between the two sets of OSPW (overall 0.84±0.10; P = 0.52). In Group OP, however, mean FFR measurement with PEPW (0.85±0.09) was numerically lower than that observed with the OSPW (0.88±0.08; P = 0.09). Level of agreement using the Bland-Altman method was higher when 2 OSPW were used for FFR assessment (-0.002 95% CI [-0.033,0.029] vs. 0.026 95% CI [-0.078, 0.130], respectively). The rate of drift was significantly lower with an OSPW compared to a PEPW (4.8% vs. 26.7% respectively, P = 0.02).

CONCLUSION

The optical sensor guidewire showed a high level of readings' agreement after simultaneous usage of 2 optical sensor guidewires. There was also significantly less drift when compared to a piezoelectric guidewire.

Invasive fractional flow reserve: Which technology is best?

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

Fractional Flow Reserve Derived from CT: The State of Play in 2020

Fractional flow reserve derived from CT is a rapidly developing technique, with an increasing burden of literature supporting its potential role in the workup of patients suspected of having coronary artery disease.