Feasibility of mitral flow assessment by echo-contrast ultrasound, part II: Experimental study on a mechanical model of the left heart

The feasibility of assessing mitral flow by means of ultrasonic monitoring of backscattered power from an echo-contrast agent in the left atrium and l eft ventricle was studied. A mechanical model of the left heart was built i n which two thin rubber balloons connected to each other in a feedback loop via two artificial heart valves mimicked the left atrium and left ventricl e, The model was driven by compressed air. Its input and output flows were measured as the functions of a pacing rate, driving pressure and artificial ly introduced mitral regurgitation, These were compared with the correspond ing data derived from the ultrasonic measurements that are based on the cor relation between echo-contrast agent concentration in the volume of interes t and the flow through it. Algorithms for quantitative estimations of forwa rd stroke volume (cardiac output) and mitral regurgitation are given. This study shows, for the first time, both analytically and experimentally, that the pulsating modulation of contrast agent concentration vs, time curves i n the ventricle and atrium volumes is closely related to the pulsating natu re of the flow in the system. It also shows that the amplitude of the atriu m concentration modulation is directly proportional to the maximum value of the incoming (to atrium) how, (C) 2000 World Federation for Ultrasound in Medicine & Biology.