Introduction Several methods of extracting arterial blood flow rates from angiography have been attempted over the past decades.1 2 However, catheter-based contrast injections in arteries can cause substantial disturbances to the baseline blood flow,3 which has limited the utilization of these methods in the clinical setting. Contrast reflux, which is the movement of contrast proximal to the catheter tip is frequently observed during antegrade angiography. The goal of this study was to evaluate the relationship between baseline hemodynamics and contrast reflux.
Methods A silicone replica of a complete circle of Willis was connected to a pulsatile flow pump (Vascular Simulations, Stony Brook, NY). Contrast injections (n=144) were performed in both the right carotid and right vertebral arteries under varying blood flow and injection conditions with high-speed (15 FPS) image acquisition. Reflux length was measured as the distance from the tip of the catheter to the most proximal point of contrast reflux. The reflux length was normalized by the vessel diameter at the catheter tip location and plotted against the ratio of the Reynolds number (a common fluid dynamics parameter) of blood flow to Reynolds number of contrast injection (figure 1). An appropriate equation was chosen to fit the data and the estimated mean blood flow from curve-fitting was compared to the true, measured blood flow. Mean blood flow was also estimated using the conventional Transit-Time method1 and the flow estimation errors between the new and conventional methods were statistically compared.
Results The relationship between the Reynolds number ratio and reflux length could be described by a sigmoidal equation (figure 1, R2=0.64). The Reflux method showed a lower error (22.8 ± 20.4%) as compared to the conventional Transit-Time method (31.7 ± 39.7%), but without statistical significance (p=0.27).
Conclusion The novel Reflux method presented in this study may have better accuracy and precision than conventional transit-time methods for estimating blood flow. Contrast reflux at the catheter tip is essentially an output of hemodynamic disturbances caused by catheter injections with baseline flow and injection parameters as input. Thus, as opposed to traditional methods, the Reflux method inherently relies on, and is robust against, these hemodynamic disturbances. Refinement of the technique is needed to improve the accuracy and precision for clinical use.
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Disclosures S. Marfoglio: 5; C; Vascular Simulations, Inc. 6; C; Vascular Simulations Inc. B. Kovarovic: None. D. Fiorella: 4; C; Vascular Simulations Inc. C. Sadasivan: 2; C; Vascular Simulations Inc. 4; C; Vascular Simulations Inc. 6; C; Vascular Simulations Inc.
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