Effect of mimic cardiac ventricle driving curve on the hydrodynamics of mechanical valvular prostheses

Yinping CHU

ABSTRACT

BACKGROUND:

Mimic pulsatile flow system is the optimal device to assess the hydrodynamic performance of mechanical valvular prostheses, but few studies concern about the performance of mimic pulsatile flow system and the effect of mimic cardiac ventricle driving curve on hydrodynamic performance of mechanical valvular prostheses.

OBJECTIVE:

To research the effect of cardiac ventricle driving curve on the hydrodynamic performance of mechanical valvular prostheses under physiological condition DESIGN, TIME AND

SETTING:

This study, a control observation, was carried out in the Hydrodynamics Laboratory,Biomedical Engineering Center, College of Architecture and Environment, Sichuan University (Chengdu, Sichuan, China)from April 1999 to February 2000.MATERIALS Mimic pulsatile flow system was adopted, with the mimic cardiac output at 4 L per minute and heart rate at75 beats per minute.

METHODS:

The mimic puisatile flow system was implanted with 25 nun Carbo Medics bileaflet prosthesis into the aortic valve position, with 27 mm Bj(o)rk-Shiley tilting disc prosthesis into the mitral valve position. Standard cardiac ventricle driving curve was employed to test the system parameters and maintain the aortic pressure at 16.0/10.7 kPa (120/80 mm Hg).Experimental liquid was a mixtrue of saline and glycerine, at a viscosity of 3.5noa·s(3.5Cp)and a density of 1.06g/cm3.The mimic flow system kept at an unchanged level of ventricular end diastolic volume, aorta arterial compliance, peripheral resistance and peripheral compliance. The coordinate on several points of standard cardiac ventricle driving curve was modified to define 4 control curves, followed by a series of procedures, such as automatic interpolation, fitting, waveform smoothing and filtering. The hydrodynamic performance of each controlled curve was also tested. MAIN OUTCOME

MEASURES:

The mean transvaivular pressure gradient, effective orifice area, closing volume and leakage volume of mechanical valvular prostheses were evaluated in five cardiac ventricle driving curves.

RESULTS:

The cardiac ventricle driving curves developed morphological changes within physiological conditions,subsequently induced a 2.9% variance of mean transvalvular pressure gradient, 1.5% variance of effective orifice area, 6.6%variance of closing volume and 3.6% variance of leakage volume.

CONCLUSION:

The cardiac ventricle driving curve has a certain effect on the hydrodynamic performance of mechanical valvular prosthesis, thereby leads to an adverse effect on the objectivity and comparability of the hydrodynamic evaluation.