How should we describe forward flow through replacement mitral valves using echocardiography?

Pressure half-time is no longer thought to reflect orifice area in normally-functioning mitral valves, but no satisfactory alternative method has been validated. Effective orifice area by the continuity equation is theoretically justified. However, we have shown no correlation against manufacturer's area in a clinical study of 40 bileaflet mechanical valves. Valve resistance is useful in native mitral stenosis, but virtually no work exists for replacement valves. We have shown no correlation against manufacturer's area in the same 40 mechanical valves. The proximal isovelocity surface area method based on the continuity equation can only be applied using the transesophageal approach; it is therefore not practical. Imaging and colour flow provide good qualitative or semiquantitative information, and together with continuous wave Doppler allow detection of obstruction for clinical diagnosis. An adequate quantitative method for research use has not yet been established.