Feasibility of Intracoronary Frequency Domain Optical Coherence Tomography Derived Fractional Flow Reserve for the Assessment of Coronary Artery Stenosis

Abstract

SummaryFrequency domain optical coherence tomography (FD-OCT) provides cross-sectional images of coronary arteries and deployed stents with micron resolution and measures lumen dimensions with excellent reproducibility. FD-OCT combined with a blood flow resistances model can overcome many limitations of conventional measures of stenosis severity based on quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS). The aim of this feasibility study was to investigate the relationship between pressure derived fractional flow reserve (FFR) and FD-OCT derived FFR, a new method for quantitative measure of stenosis severity that estimates the blood flow resistance and microvascular resistance of the vessel segments imaged by FD-OCT. A total of 26 coronary stenoses in 20 patients were studied consecutively with QCA, pressure derived FFR, and FD-OCT. There was a moderate but significant correlation between pressure derived FFR and FD-OCT derived FFR (r = 0.69, P < 0.001). Bland-Altman analysis showed that the mean differences between pressure derived FFR and FD-OCT derived FFR were 0.05 ± 0.14 (limits of agreement: -0.09 to 0.19). The root mean square error (RMSE) between FD-OCT derived FFR and pressure derived FFR was found to be ± 0.087 FFR units. FD-OCT derived FFR has the potential to become a valuable tool for the assessment of coronary artery stenosis. ( 1-4) Intracoronary optical coherence tomography (OCT) provides cross-sectional images of coronary arteries and deployed stents with resolution 10-15 times higher than intravascular ultrasound (IVUS). OCT is used for anatomic and morphological assessment of coronary stenosis and provides lumen measurements with excellent reproducibility. [5][6][7][8] OCT also provides information about plaque vulnerability, calcification, and other parameters which helps in guiding the procedure along with diagnostics. The frequency domain OCT (FD-OCT) systems provide faster image acquisition speeds, higher frame rates, and greater scan depths as compared to time domain OCT (TD-OCT) systems. FD-OCT combined with a blood flow model can overcome many limitations of conventional measures of stenosis severity based on QCA and IVUS. The main objective of this feasibility study was to investigate the potential of FD-OCT derived FFR for the assessment of coronary artery stenosis. Through the volumetric analysis of FD-OCT images, FFR was calculated from the blood flow resistance and the microvascular resistance. A comparison between FD-OCT derived FFR and pressure derived FFR was also conducted in this study. MethodsA total of 26 coronary stenoses in 20 patients with stable angina and/or ischemia documented on exercise stress test were studied consecutively with QCA, pressure derived FFR, and FD-OCT during diagnostic coronary angiography. The study was approved by Galway clinical research ethics committee and informed consent for all procedures was obtained from each patient. Eligible patients had a single de novo stenosis in a native coronary artery with diameter stenosis...

Identification of the State of Maximal Hyperemia in the Assessment of Coronary Fractional Flow Reserve Using Non-Invasive Electrical Velocimetry

“…Although FFR, which is determined under maximal hyperemia state, is considered as the physiology standard in the functional assessment of intermediate coronary stenosis, 13,14) the state of maximal hyperemia induced by intravenous adenosine administration is somewhat uncertain during the FFR measurement in clinical practice. The availability of approach- es that can confirm the state of maximal hyperemia could increase the accuracy of FFR measurements.…”

Optical imaging techniques for vulnerable plaque detection

“…Some of the techniques used in non-invasive imaging of the microcirculatory system comprise the capillaroscopy, laser Doppler perfusion, dynamic laser speckle imaging and video capillaroscopy [18]. However, Zafar, Sharif, and Leahy [19] have discovered that the non-invasive techniques mentioned above have a limitation such that they only can image blood vessels that are close to the skin [20]. To solve this, Spaide, Klancnik and Cooney [21] suggest that optical coherence tomography can be employed to attain high microcirculation morphology, but it will still do not help in the viewing of vessels found in deeper depth in the body [22].…”

“…Furthermore, angiography develops threedimensional figure though a series of two-dimensional images [14]. Intravascular imaging based on the catheter has also been acknowledged to be one of the best modalities to be used in catheterisation of patients [20]. Figure 6 shows the intravascular photoacoustic technique.…”

“…Some of the best tools for making FD-OCT measurements can be Lightlab imaging software. Zafar et al [34] studied 20 coronary stenoses involving 15 patients, and they found that FD-OCT is more efficient than the IVUS in the identification of severe coronary stenosis. The FD-OCT can work to collect various measurements without needing the inflation of balloons thus it is regarded as being a non-occlusion technique.…”

“…The FD-OCT can work to collect various measurements without needing the inflation of balloons thus it is regarded as being a non-occlusion technique. There are reported incidences of miscalculations using the time domain of optical coherence tomography (TD-OCT) technique (occlusive technique) when using balloon inflation for intraluminal dimensions measurements [34].…”