Variability of regurgitation in Bjork-Shiley mitral valves and relationship to disc occluder design: An in vitro two-dimensional color-Doppler flow mapping study

Background and aims of the study: Normal prosthetic valves have regurgitation that varies according to valve type and design. The Bjork-Shiley prosthetic mitral valve is a tilting disc valve that has undergone design changes since its introduction. From 1969 to 1981, Delrin®, was used to make the disc occluder. After 1971, the occluder was made from Pyrolite® (i.e. Conical and Radiopaque-Spherical valves). Our aim was to quantify the regurgitation of Delrin and Radiopaque-Spherical Bjork-Shiley prosthetic mitral valves with color-Doppler flow mapping in an in vitro model that simulates transesophageal echocardiography imaging. Materials and methods: Normal unimplanted Bjork-Shiley Delrin (BSD), Bjork-Shiley Radiopaque-Spherical (BSS) and explanted (17 ± 3 yrs) BSD valves (25, 27, and 29 mm) were studied in a pulse duplication system. The regurgitant leakage volume of the valves was measured with an electromagnetic flow probe at flow rates of 3.0, 5.0, and 7.0 L/min, a pulse rate of 70 beats/min, and a mean systemic pressure of 100 mmHg. Color-Doppler flow mapping was performed with a 3.7 MHz transducer positioned on the atrial chamber at an image depth of eight centimeters. The maximal regurgitant jet areas were measured off-line and averaged from three beats. Results: Maximal jet area, measured with color-Doppler flow mapping, correlated with regurgitant leakage volume (r = 0.82). Normal unimplanted and explanted BSD valves had greater regurgitant leakage volumes and jet areas than BSS valves for all sizes and flow rates studied. Regurgitant jet areas of normal unimplanted and explanted BSD valves were similar. Conclusion: Knowledge of the type of Bjork-Shiley valve is important in the clinical evaluation of regurgitation severity by transesophageal echocardiography. The echocardiographic appearance of regurgitation of BSD valves does not necessarily imply valve dysfunction.