Q-PULS: A New Quasi-Physiological Pulsatile Extracorporeal Model to Simulate Heart Function Substituting Animal Experiments

Background: Inventing new surgical procedures is demanding. A computer-controlled extracorporeal circulation system allows for testing of an explanted porcine heart simulating a variety of physiological and functional parameters. Mitral valve function can be assessed before and after induced valve insufficiency and after valve repair. Accordingly, technique and instruments can be modified in the early stages of prototype development.

Methods: In diastole, the left atrium is passively filled through the reservoir. Loading pressure of the atrium can be achieved through a metered water column inside the reservoir. Shut-off valves are installed in the return line between aorta and reservoir and downstream of the supply line to the atrium respectively enabling a widely variable adjustment of flow rates. To simulate systole, a linear motor driven piston pumps volume through the forward movement across the left ventricle and the aorta into the return line back to the reservoir. The backward movement of the piston removes volume from the ventricle. An additional circulatory pump compensates for an undesired total emptying of the heart chambers. The linear pump consists of a processor-controlled linear motor whose rotor is connected to the piston rod. The processor control of the linear pump allows for various settings of flow rate and velocity using special software. 10 isolated porcine hearts were used. The mitral valve was hemodynamically tested before and after induced valve insufficiency or repair and controlled with echocardiography. Leaflet movement was filmed using a USB-probe camera.

Results: With a piston diameter of 55 mm, 80 mm stroke, and 1 m/s speed a volume of 190 ml is pumped with each forward movement of the piston at a heart rate of up to 73 bpm. Thus, under these conditions a cardiac output of up to 13.9 l/min can be achieved. Piston speed, acceleration, and deceleration, however, are further adjustable from 0.01 to 3.5 m/s so that a maximum frequency up to 205 bpm can be achieved. In addition, duration of diastole can be extended or shortened. Furthermore, the processor control software allows configuring the beats in an irregular rhythm thereby simulating extrasystoles or pauses.

Conclusion: This new model allows a controllable pulsation, loading and unloading of the porcine heart in a wide range. Thus, function of the leaflets as well as results of the repair can be qualitatively and quantitatively evaluated under nearly physiological conditions.