In-Vitro Pulsatile Flow Measurement in Prosthetic Heart Valves: An Inter-Laboratory Comparison

One of the first steps in qualifying a new prosthetic valve for eventual clinical use is preclinical flow performance testing in vitro. Such testing is typically performed in an in-vitro test system that simulates the pumping mechanics of the left ventricle of the heart, generally referred to as a pulse duplicator or duplicator. Historically, test results in these systems have varied from duplicator to duplicator. This collaborative effort between heart valve manufacturers and the Food and Drug Administration (FDA) was designed to evaluate the variability of the pulse duplicator test technology for pulsatile flow performance measurement in an interlaboratory round robin.

The participants jointly developed and followed a limited test protocol based on accepted methods outlined in the International Standards Organization 5840: Cardiovascular Implants - Cardiac Valve Prostheses, and in the FDA Replacement Heart Valve Guidance. One 25 mm valve, each of four basic designs, was circulated to test centers which included four manufacturers and two FDA duplicators. The pressure drop and regurgitation data were then collected and summarized by the FDA.

Considerable variation was observed in hydrodynamic performance measures of pressure drop across the valve and back flow leakage through the valve among the different duplicators. Despite the variations seen in these measures, the results from all centers showed that the valves conformed to certain minimum performance criteria.

Despite the fact that the valves would have been judged to have met Minimum Performance Requirements of effective orifice area and regurgitant fraction, as specified in the international standard, variations in measurements existed among duplicators. Valve manufacturers should use a reference valve of similar design in hydrodynamic performance testing to assess the individual measurement conditions in the duplicator.