Effect of simulated valvular stenoticity on predicted flow area for a bileaflet valve using the gorlin equation

The possibility that the discharge coefficient (C(d)) for a mechanical heart valve (MHV) is affected by valvular stenosis is addressed. A 29 mm bileaflet (St. Jude Medical) mitral valve is tested on a cardiovascular duplicator (CVD) in its normal state and under two degrees of simulated stenosis. Stenoticity is simulated by bracing the occluders such that full opening is impossible. The pressure drop through the valve is described by a two-term second-order polynomial in flow, from which it is shown that the C(d) should be a nonlinear function of the flow rate through the valve. The average difference between measured and calculated areas decreased from 74%, when a constant value of 0.7 was used for the C(d), to 3.7%, when the C(d) was a nonlinear function of the flow rate