VARIABILITY OF REGURGITATION IN BJORK-SHILEY MITRAL-VALVES AND RELATIONSHIP TO DISC OCCLUDER DESIGN - AN IN-VITRO 2-DIMENSIONAL COLOR-DOPPLER FLOW MAPPING STUDY

Background and aims of the study: Normal prosthetic valves have regurg itation that varies according to valve type and design. The Bjork-Shil ey prosthetic mitral valve is a tilting disc valve that has undergone design changes since its introduction. From 1969 to 1981, Delrin(R), w as used to make the disc occluder. After 1971, the occluder was made f rom Pyrolite(R) (i.e. Conical and Radiopaque-Spherical valves). Our ai m 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 duplicatio n system. The regurgitant leakage volume of the valves was measured wi th 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 transdu cer positioned on theatrial chamber at an image depth of eight centime ters. The maximal regurgitant jet areas were measured offline and aver aged 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 regurgi tant leakage volumes and jet areas than BSS valves for all sizes and n ow rates studied. Regurgitant jet areas of normal unimplanted and expl anted BSD valves were similar. Conclusion: Knowledge of the type of Bj ork-Shiley valve is important in the clinical evaluation of regurgitat ion severity by transesophageal echocardiography. The echocardiographi c appearance of regurgitation of BSD valves does not necessarily imply valve dysfunction.