Assessing the impact of turbulent kinetic energy boundary conditions on turbulent flow simulations using computational fluid dynamics.

Computational fluid dynamics has been widely used to study hemodynamics, but accurately determining boundary conditions for turbulent blood flow remains challenging. This study aims to investigate the effect of patient-specific turbulence boundary conditions on the accuracy of turbulent flow simulation. Using a stenosis model with 50% severity in diameter, the post-stenosis turbulence flow region was simulated with different planes to obtain inlet boundary conditions and simulate downstream flows. The errors of simulated flow fields obtained with turbulence kinetic energy (TKE) boundary data and arbitrary turbulence intensity were compared. Additionally, the study tested various TKE data resolutions and noise levels to simulate experimental environments. The mean absolute error of velocity and TKE was investigated with various turbulence intensities and TKE mapping. While voxel size and signal-to-noise ratio of the TKE data affected the results, simulation with SNR > 5 and voxel size < 10% resulted in better accuracy than simulations with turbulence intensities. The simulation with appropriate TKE boundary data resulted in a more accurate velocity and turbulence field than those with arbitrary turbulence intensity boundary conditions. The study demonstrated the potential improvement of turbulent blood flow simulation with patient-specific turbulence boundary conditions, which can be obtained from recent measurement techniques.

Diagnostic performance of a vessel-length-based method to compute the instantaneous wave-free ratio in coronary arteries.

The instantaneous wave-free ratio (iFR) is a recently introduced vasodilator-free index to assess the functional severity of coronary stenosis in the resting state, while fractional flow reserve (FFR) is the gold standard index in hyperemia. The computed instantaneous wave-free ratio (CT-iFR) is a noninvasive method to estimate iFR using computer simulations. Here, we developed a vessel-length-based CT-iFR method in patient-specific models of coronary arteries. This method was implemented by coupling a three-dimensional computational fluid dynamics model with a lumped parameter model (LPM) of coronary circulation in a non-hyperemic resting state. A time-varying resistance in the LPM was used for the iFR simulation. In total, 50 coronary vessels of 32 patients were computed, and their CT-iFR values were compared with clinically measured iFRs to evaluate the diagnostic performance of the present CT-iFR method. The area under the receiver operating characteristics curve of CT-iFR validation was 0.93. In diagnostic performances of CT-iFR, accuracy, sensitivity, and specificity were 86%, 83.3%, and 86.8%, respectively. These results indicate that this CT-iFR method can be used as a pre-operative aid to establish a percutaneous coronary intervention strategy as a noninvasive alternative to iFR.

Presencia de trombo y erosión de placa en pacientes con angina vasospástica mediante tomografía de coherencia óptica / Thrombus and plaque erosion characterized by optical coherence tomography in patients with vasospastic angina

Introducción y objetivos: La angina vasospástica (AVS) puede causar daño endotelial y formación de trombo. El objetivo de este estudio es evaluar mediante tomografía de coherencia óptica (OCT) la incidencia de trombo y las características de la placa en segmentos con espasmo coronario comparados con segmentos sin espasmo en pacientes con sospecha de AVS. Métodos: Se incluyó a 183 pacientes con sospecha de AVS. Para el diagnóstico de AVS se realizó test de provocación con ergonovina en todos los pacientes, excepto aquellos con espasmo espontáneo. Se analizaron por OCT todas las lesiones diana. Se definió erosión de placa como la presencia de trombo adherido a una capa fibrosa intacta y visualizada en múltiples cortes de OCT. Resultados: Se compararon 109 segmentos con espasmo (93 pacientes) con 55 segmentos sin espasmo (39 pacientes). Se observó una mayor incidencia de trombo en los segmentos con espasmo coronario que en los segmentos sin espasmo (el 28,4 frente al 7,3%; p = 0,026) y el tamaño del trombo fue mayor en los primeros que en los segundos (0,26 ± 0,50 frente a 0,04 ± 0,01 mm2; p = 0,023). Se observó ateroma de capa fina con mayor frecuencia en segmentos sin espasmo que en aquellos con espasmo (el 16,4 frente al 1,8%; p = 0,006). La erosión de la placa fue más prevalente en los segmentos con espasmo que en los segmentos sin espasmo (el 25,7 frente a 5,4%; p = 0,001). Conclusiones: La presencia de trombo y erosión de placa analizados por OCT fue más frecuente en los segmentos con espasmo que en aquellos sin espasmo en pacientes con sospecha de AVS. Estos hallazgos apuntan a un potencial beneficio del tratamiento antiagregante para estos pacientes (AU)

Introduction and objectives: Vasospastic angina (VSA) can result in endothelial damage and thrombus formation. The aim of this study was to evaluate the incidence of thrombus and plaque characteristics at coronary spasm segments compared with nonspasm segments by using optical coherence tomography (OCT) in patients with suspected VSA. Methods: One hundred and eighty-three patients with suspected VSA were enrolled in this study. The ergonovine provocation test was performed in all patients for the diagnosis of VSA except in patients with spontaneous spasm. All target lesions were analyzed by OCT. Plaque erosion was defined as the presence of attached thrombus overlying an intact fibrous cap and visualized plaque on multiple adjacent OCT frames. Results: One hundred and nine spasm segments (93 patients) were compared with 55 nonspasm segments (39 patients). Thrombus was more frequently seen at spasm segments than at nonspasm segments (28.4% vs 7.3%; P = .026) and thrombus size was larger at spasm segments than at nonspasm segments (0.26 ± 0.50 mm2 vs 0.04 ± 0.01 mm2; P = .023). Thin-cap fibroatheroma was more frequently seen at nonspasm segments than at spasm segments (16.4% vs 1.8%; P = .006). Plaque erosion was more prevalent at spasm segments than at nonspasm segments (25.7% vs 5.4%; P = .001). Conclusions: Thrombus and plaque erosion were more common at spasm segments than at nonspasm segments assessed by OCT in patients with suspected VSA. These findings suggest the potential benefit and treatment role of antiplatelet therapy in vasospastic angina (AU)

Thrombus and Plaque Erosion Characterized by Optical Coherence Tomography in Patients With Vasospastic Angina.

INTRODUCTION AND OBJECTIVES: Vasospastic angina (VSA) can result in endothelial damage and thrombus formation. The aim of this study was to evaluate the incidence of thrombus and plaque characteristics at coronary spasm segments compared with nonspasm segments by using optical coherence tomography (OCT) in patients with suspected VSA. METHODS: One hundred and eighty-three patients with suspected VSA were enrolled in this study. The ergonovine provocation test was performed in all patients for the diagnosis of VSA except in patients with spontaneous spasm. All target lesions were analyzed by OCT. Plaque erosion was defined as the presence of attached thrombus overlying an intact fibrous cap and visualized plaque on multiple adjacent OCT frames. RESULTS: One hundred and nine spasm segments (93 patients) were compared with 55 nonspasm segments (39 patients). Thrombus was more frequently seen at spasm segments than at nonspasm segments (28.4% vs 7.3%; P = .026) and thrombus size was larger at spasm segments than at nonspasm segments (0.26 ± 0.50 mm2 vs 0.04 ± 0.01 mm2; P = .023). Thin-cap fibroatheroma was more frequently seen at nonspasm segments than at spasm segments (16.4% vs 1.8%; P = .006). Plaque erosion was more prevalent at spasm segments than at nonspasm segments (25.7% vs 5.4%; P = .001). CONCLUSIONS: Thrombus and plaque erosion were more common at spasm segments than at nonspasm segments assessed by OCT in patients with suspected VSA. These findings suggest the potential benefit and treatment role of antiplatelet therapy in vasospastic angina.