PC210. Turbulence in Saphenous Vein Bypass Grafts by Duplex Ultrasound Imaging

Abstract

Turbulent flow distal to stenoses in saphenous vein bypass grafts (SVBG) may influence vein graft remodeling, including intimal hyperplasia. This study aimed to develop and validate ultrasound indices for turbulence intensity that may be useful in predicting stenosis, occlusion, and remodeling in SVBG. Twenty-five patients with leg SVBGs underwent regularly scheduled duplex ultrasound studies and simultaneous measurement of turbulence indices, using a Philips iU22 ultrasound model and 9-3 MHz linear transducer. Fourteen patients had significant stenosis and downstream turbulence. In each of these 14 patients, color Doppler at maximal stenosis was used to determine the color scale to avoid aliasing. Then color Doppler video loops were recorded downstream of the stenosis. Color-scale videos were recorded in a normal region absent of stenosis for comparison. Custom image analysis algorithms were used to determine percentage area reverse flow (%ARF), reverse mean velocity (RMV), and turbulent flow volume (TFV = %ARF × RMV) as surrogates for turbulence intensity. Peak %ARF was 20 ± 21 in normal segments and 56 ± 27 in turbulent segments (P = .0002). Peak RMV was 7.7 ± 7.6 cm/s in normal segments and 16.7 ± 7.7 cm/s in turbulent segments (P = .01). Peak TFV was 1.3 ± 1.3 m/s in normal segments and 6.5 ± 3.4 m/s in turbulent segments (P = .0001), and correlated with upstream peak systolic velocity (fig). Surrogates for SVBG turbulence can be detected and quantified using duplex ultrasound imaging. These measures correlate with percent stenosis and may predict stenosis and remodeling. Turbulence imaging may also be useful in situations where a stenosis is inadequately imaged on ultrasound or its hemodynamic significance is uncertain. A larger study with appropriate follow-up to determine clinical and ultrasound outcomes in these patients’ SVBGs is underway.