Effect of catheter placement on 3-D velocity profiles in curved tubes resembling the human coronary system

Novel measurement techniques based on intravenous ultrasound (IVUS) technol ogy ('IVUS-Flowmetry') require the location of a catheter inside the corona ry bed. The present study quantifies disturbances in the 3-D velocity profi le induced by catheter placement inside a tube, applying computational flui d dynamics. Two curved, circular meshes (radius K = 0.025 m and K = 0.035 m ) with and without a catheter inside the lumen were applied. The catheter w as located at the inner curve, the outer curve and at the top position. Bou ndary conditions were: no slip on the wall, zero stress at the outlet, unif orm inflow with entrance velocities of 0,1, 0.2 and 0.4 m/s, Curvature-asso ciated centrifugal forces shifted the maximal velocity to the outer curve a nd introduced two symmetrical vortices. Additional catheter placement redis tributed the 3-D axial velocity field away from the catheter, which was acc ompanied by the appearance of multiple low-strength vortices. In addition, peak axial velocity increased, peak secondary velocities decreased, axial p ressure drop increased and shear stress increased. Flow calculations simula ted to resemble IVUS-based flowmetry changed by only 1% after considering s econdary velocity. In conclusion, placement of a catheter inside a curved t ube resembling the human coronary system changes the velocity field and red uces secondary patterns. The present study supports the usefulness of catbe ter-based flowmetry during resting flow conditions. During hyperemic flow c onditions, flow measurements might be accompanied by large axial pressure d rops because the catheter, itself, might act as a significant stenosis, (C) 1999 World Federation for Ultrasound in Medicine & Biology.