Direct Ex Vivo Measurement of the Real Geometric Orifice Area to Assess the Hemodynamic Performance of Bioprosthetic Heart Valves

Objectives: Induced by the initiation of the PAR I trial, the debate about the clinical evidence of the so-called patient-prosthesis mismatch (PPM) arose again. In this context it was discussed which valve specific parameter has the biggest evidence for the PPM and therefore the geometric orifice area (GOA) was pointed out as an important factor. It was also shown, that the determination of this parameter is very difficult. We developed a setup combined with an in-house developed software tool, which enables us to quantify the “real” GOA even as a function of time.

Methods: Commercially available surgical aortic bioprosthetic heart valves from different manufacturers were tested in a FDA / DIN conform Pulse Duplicator System (ViVitro Labs Inc., Victoria, Canada). The system was operated with isotonic saline solution at room temperature under various hemodynamic conditions. Imaging of the prostheses was performed with 2,000 fps using a digital high-speed camera connected to a rigid 0° laparoscopic endoscope (Richard Wolf GmbH, Knittlingen, Germany). The high-speed recordings were segmented and analyzed using an in-house developed software tool with graphical user interface. The image processing results in an orifice area waveform as function of time.

Results: It was possible to determine the real GOA of the heart valve bioprostheses exactly and under different hemodynamic setups. Furthermore it was clearly demonstrated, that this GOA is a dynamic process over the whole ejection period, which significantly differed from the maximum reached GOA. First results from different valves and in different hemodynamic setups showed, that the GOA is varying extremely over the whole ejection period and from the hemodynamic situation.

Conclusions: This standardized setup enables a semi-automated quantitative characterization of prosthetic valves´ orifice area as a function of time depending on highly reproducible flow conditions allowing the comparison of different valve types. Analyzing the resulting opening area waveform allows to determine the opening and closing process as well as the leaflets´ behavior during the ejection showing more or less fluttering. Identifying and implementing further quantitative parameter in our software will provide an informative basis for the performance evaluation of different types of bioprosthetic heart valves in future.