Letter to the Editor
A novel noninvasive method for measuring fractional flow reserve through three-dimensional modeling

Coronary stenosis with lumen diameter reduction greater than 50% is recognized as coronary artery disease (CAD) [1-4]. Fractional flow reserve (FFR) is an epicardial lesion-specific parameter to determine the functional coronary stenosis, which is determined by pressure difference and resistance [5-8]. Previous studies have demonstrated that FFR guided percutaneous coronary intervention (PCI) could improve outcomes compared with anatomical invasive coronary angiography (ICA) guided PCI [6-10]. This study aims to overcome the deficiencies of invasive FFR and create a novel noninvasive FFR (FFRni).

A 70-year-old female patient, diagnosed with CAD, stable angina pectoris, cardiac function III, essential hypertension III (very high-risk group), with blood pressure of 140/85 mm Hg, was enrolled in as a pilot study.

Coronary computed tomography angiography (CCTA) was performed using multi-detector computed tomography scanners (Lightspeed 16 Pro). Original images were spilt into thin layers and directly exported into imaging control software MIMICS and processed to form an image sequence. Three-dimensional (3D) geometric models of the narrow coronary arteries including the right coronary artery (RCA), left anterior descending coronary (LAD) and left circumflex artery (LCX) were reconstructed and exported. Then, the geometric model was meshed with 3D Flotran elements in ANSYS software. Finite element analysis (FEA) was applied to analyze the velocity and pressure distribution of selected coronary arteries. Given boundary conditions including average velocity measured by transthoracic Doppler echocardiography with an ultrasound system (Sequoia C256) were applied in an inlet of 3D model. By setting the proper iteration time, the calculation went smoothly. ICA, as the “gold standard”, was performed with standard techniques.

Invasive coronary angiography indicated that there was around 80% stenosis in the proximal RCA (Figure 1 A). Mild (about 30%) stenosis in the proximal LAD and a diffuse lesion of the LCX (the narrowest was 80%) could also be quantified (Figure 2 A). Additionally, the coronal section of CCTA images demonstrated moderate (around 60%) obstructive stenosis in the proximal RCA (Figure 1 B). The cross-sectional images indicated 30% stenosis in the proximal and first branch segment of the LAD and diffuse patchy calcified plaques in the LCX leading to intermediate (50%) stenosis (Figure 2 B). The diagnostic...


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