Haematological Evaluation of the Björk-Shiley Tilting Disc Valve Prosthesis in Isolated Aortic Valvular Disease

Abstract

All the 147 long-term surviving patients, following 161 consecutive operations of isolated aortic valvular lesions with the Björk-Shiley tilting disc valve, were investigated haematologically before, and 7 months after surgery. Seventy of these patients were re-examined 28 months after operation. The present material showed no signs of anaemia after operation and serum iron remained at normal levels, although no iron was administered during the entire follow-up period. The degree of haemolysis, evaluated by the serum lactic de-hydrogenase activity (LDH), increased significantly with the angiographical degree of paravalvular regurgitation. Even slight and haemodynamically insignificant paraprosthetic leaks were associated with an increased haemolysis, probably due to a regurgitant jet causing turbulence during diastole. Turbulence, acting as an extra prosthetic factor, is considered a determinant of haemolysis after aortic valve replacement with the Björk-Shiley valve. The degree of haemolysis was related neither to the size of the prosthesis nor to its in vivo gradient at rest, but increased significantly after brief, maximal exercise. The effects of aortic valve replacement on platelet count and other haematological parameters in the three groups of aortic valvular disease are discussed. With the passage of time, and despite absence of iron treatment, the haemoglobin and serum iron concentrations were maintained, while the degree of haemolysis showed a slight decrease.

The Bjork-Shiley tilting disc valve, with its pressure-flow characteristics and non-overlapping disc, seems to combine minimal turbulence and mechanical crushing, thus resulting in a low degree of erythrocyte destruction.