Mitral valve replacement. A comparative clinical and haemodynamic study of the new Lillehei-Kaster and Björk-Shiley prostheses.

A comparison is made between the clinical and haemodynamic results after mitral valve replacement with the Lillehei-Kaster and the Björk-Shiley disc valve prostheses, which were used alternatively in 54 patients with isolated mitral valve disease. No difference in functional improvement in the two groups was noted. Haemodynamic studies indicated a striking decrease in left atrial and pulmonary artery pressure, irrespective of the type of prosthesis inserted. Cardiac output incresed after operation, but was significantly different from the pre-operative value only in patients with the Björk-Shiley prosthesis, which also had a more favourable relationship between cardiac output and oxygen uptake during excercise than the Lillehei-Kaster prosthesis. One major advantage of the Björk-Shiley prosthesis is probably its favourable ration between tissue diameter and orifice area in contrast to the relatively large seating ring with a more unfavourable corresponding ratio in the Lillehei-Kaster prosthesis. In addition, the former valve possesses a more definite ability to increase its effective valve area during exercise.