Clinical and hemodynamic results of cardiac valve replacement with the Monostrut Björk-Shiley prosthesis

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Between May 1983 and April 1986, 318 patients underwent cardiac valve replacement with the Monostrut Björk-Shiley prosthesis. There were 136 aortic valve replacements, 128 mitral valve replacements, and 54 multiple replacements. A total of 373 valves were implanted. Associated procedures were done in 79 (25%) of the patients. Hospital (30-day) mortality rate was 5.6% (18 patients): 2.9% (n = 4) after aortic, 7.8% (n = 10) after mitrals and 7.4% (n = 4) after multiple valve replacement. Follow-up was obtained in all 300 operative survivors, for a total of 500 patient-years (mean 18 months). Actuarial survival rate, excluding operative deaths, at 4 years was 94.7% +/- 1.5% (mean +/- standard error of the mean). There were 16 thromboembolic episodes (3.2/100 patient-years). Freedom from all valve-related complications was 87% +/- 2.4% at 3 1/2 years. Neither valve thrombosis nor structural failure has been observed. Eighty percent of the patients are in New York Heart Association functional class I. Forty-two patients (26 with aortic and 16 with mitral valve replacement) underwent cardiac catheterization a mean of 6 1/2 months after the operation. In the aortic position, peak gradients were an average of 6.9 +/- 1.2 mm Hg. Mean systolic gradients were 12.4 +/- 6.3 mm Hg and did not increase with exercise. In the mitral position, end-diastolic gradients were an average of 2.1 +/- 2 mm Hg and mean gradients, 5.9 +/- 2 mm Hg. Discharge coefficient (estimated orifice area/geometric area) was 0.63 +/- 0.2 for the aortic and 0.53 +/- 0.2 for the mitral prostheses. Disc opening was maximal in most patients. These results indicate that the Monostrut prosthesis has a low rate of thromboembolic events, no structural failures or thrombotic obstructions and excellent hemodynamic performance, especially in the small aortic sizes (discharge coefficient for 19 and 21 mm valves, 0.77).