A pulsatile flow model for in vitro quantitative evaluation of prosthetic valve regurgitation

A pulsatile pressure-flow model was developed for in vitro quantitative col or Doppler flow mapping studies of valvular regurgitation. The flow through the system was generated by a piston which was driven by stepper motors co ntrolled by a computer. The piston was connected to acrylic chambers design ed to simulate "ventricular" and "atrial" heart chambers. Inside the "ventr icular" chamber, a prosthetic heart valve was placed at the inflow connecti on with the "atrial" chamber while another prosthetic valve was positioned at the outflow connection with flexible tubes, elastic balloons and a reser voir arranged to mimic the peripheral circulation. The flow model was fille d with a 0.25% corn starch/water suspension to improve Doppler imaging. A c ontinuous flow pump transferred the liquid from the peripheral reservoir to another one connected to the "atrial" chamber. The dimensions of the flow model were designed to permit adequate imaging by Doppler echocardiography. Acoustic windows allowed placement of transducers distal and perpendicular to the valves, so that the ultrasound beam could be positioned parallel to the valvular flow. Strain-gauge and electromagnetic transducers were used for measurements of pressure and flow in different segments of the system. The flow model was also designed to fit different sizes and types of prosth etic valves. This pulsatile flow model was able to generate pressure and fl ow in the physiological human range, with independent adjustment of pulse d uration and rate as well as of stroke volume. This model mimics flow profil es observed in patients with regurgitant prosthetic valves.