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Background and Aims of the Study: The Björk-Shiley Delrin (BSD) disc heart valve was first used clinically in 1969. We estimate that as of January 1996, no more than 7,000 patients may be alive with the BSD valve., Methods: We reviewed the published reports of clinical experience with the BSD valve in addition to the records regarding BSD valves returned to Shiley Incorporated. Measurements of the maximum radial gap, static leak flow rate and inspection of the Delrin disc for wear were obtained., Results and Conclusions: We concluded that clinically important regurgitation, due to disc wear, was rare but may occur. Larger prostheses, in general, showed greater disc wear than smaller sized valves. There were no reports of fracture of the Delrin disc. Two cases of inlet strut fracture were reported. Late disc embolization, in the absence of inlet strut fracture, occurred in two patients following surgical manipulation. Disc wear did not cause abnormal valve opening or closing although increased regurgitation may occur.

Background and Aims of the Study: Normal prosthetic valves have regurgitation that varies according to valve type and design. The Björk-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 Björk-Shiley prosthetic mitral valves with color-Doppler flow mapping in an in vitro model that simulates transesophageal echocardiography imaging., Materials and Methods: Normal unimplanted Björk-Shiley Delrin (BSD), Björk-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 offline 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 Björk-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.

It has been estimated that up to 7,000 patients with Björk-Shiley Delrin (BSD) heart valves may be alive as of January 1996, the range of implant durations being from 15 to 27 years. The clinical question was whether these BSD valves could be expected to continue to function satisfactorily or if prophylactic replacement might be warranted. The data presented in this supplement suggest that clinically important regurgitation due to wear of the Delrin disc may occur in some BSD valves years after implantation. Normally functioning valves, however, show more regurgitation than Björk-Shiley Radiopaque Spherical disc valves. Some regurgitation does not therefore necessarily indicate dysfunction of BSD valves. There were only two reported cases of inlet strut fracture. However, there are no reports of catastrophic failure associated with fracture of the Delrin disc. Engineering studies showed no reason to suspect an increased rate of failure of the Delrin disc due to fracture or fatigue. All of the data suggested that the BSD valve will continue to provide years of continuing service. Disc wear, if it occurred, was at a rate which allowed adequate time for diagnosis and non-emergency treatment. The data showed no reason to remove BSD valves prophylactically. Patients should be treated on an individual basis, according to the function of their own valve or valves.

Background and Aims of the Study: An in vitro study of the mechanics of closure of Björk-Shiley convexo-concave (BSCC) valves is presented in order to investigate the mechanics of outlet strut fracture reported in a small fraction of the implanted valves., Materials and Methods: Four BSCC 29 mm valves instrumented with strain gages on the outlet strut legs were mounted in the mitral position of an axisymmetric flow chamber of a mock pulsatile flow loop. Measurements of the pressure field in the vicinity of the occluder, closing velocity of the occluder tip in the major orifice, and the impact force between the occluder and outlet strut at the instant of valve closure were obtained at a range of physiologic flow rates., Results: The results indicated an uneven pressure distribution on the occluder associated with a tendency for the occluder to over-rotate and induce loads on the outlet struts. The impact loads on the outlet struts were asymmetric with load on one leg being larger than the other by up to 25%. These results are consistent with single leg separation preceding outlet strut fracture in most of the valve failures reported. Orientation of the valve with respect to the mitral orifice (major orifice towards the top or bottom) did not significantly affect the loads on the outlet strut. A significant variation in the impact loads of the four valves was measured for identical experimental conditions suggesting that valve specific factors influence outlet strut loads., Conclusions: This study provided an understanding of the cause-effect relationship between valve dynamics and outlet strut fracture.