Inter-laboratory comparisons: approaching a new standard for prosthetic heart valve testing in vitro.

Current standards governing the evaluation of prosthetic heart valve designs have come under scrutiny. Generally, standards require measurements of pressure drops and regurgitant flow. While this information is important in the characterization of valve performance, these standards are both insufficient and ambiguous. Their insufficiency is due to the fact that they do not cover issues related to thrombosis and structural damage, and their ambiguity is demonstrated by the fact that different pulse duplicators will produce different results for nominally the same set of conditions. While the insufficiency of the current standards has recently been addressed, the ambiguity has not been addressed in a systematic way except for one particular study involving two pulse duplicator systems. This paper explores physical sources for disagreement in pressure and flow measurements between pulse duplicators, and suggests ways to account for them. By considering these physical phenomena, standards can be developed for testing chambers that improve similarity between systems. This should not compromise innovation in the design of new pulse duplicators, which may be necessary to address additional concerns besides the pressure and flow characteristics of the valve.