CORRELATION BETWEEN LDA AND ULTRASOUND HEART CATHETER MEASUREMENTS INA STENOSED ARTERIAL MODEL

Ultrasound heart catheters are used to measure the velocity in coronar y arteries. However, the act of introducing a catheter into the vessel disturbs the very flow being measured. We used laser Doppler anemomet ry to measure the velocity distribution in an axially symmetric model, both with and without a catheter inserted The catheter reduced the ce nter-line velocity by as much as 60 percent at a distance of 2 mm down stream from the catheter, and by as much as 25 percent at a distance o f 10 mm. This means the velocity measured with an ultrasound catheter does not show the maximum velocity of the undisturbed flow in the tube center. In the constriction, however, the measured velocities with th e LDA and ultrasound catheter are almost the same. Thus, catheter meas urements in the stenosis achieve accurate results. The velocity profil e in the stenosed areas is flattened over nearly the whole cross secti on. The velocity is extremely reduced only close to the wall. The meas urements outside of the stenosis lead to large differences which need to be studied carefully in the future. The disturbed flow finally disa ppeared 15 mm downstream of the catheter. The measurements were done a t steady flow using a glycerine water solution with a dynamic viscosit y of 4.35 mPas. In future studies, these experiments will be repeated for pulsatile flow conditions using non-Newtonian blood-like fluids.