Haemodynamic evaluation of the convexo-concave Björk-Shiley prosthesis in patients with narrow aortic annulus.

A late haemodynamic re-evaluation at rest and during exercise was performed in 22 patients with isolated aortic valvular disease and narrow aortic annulus, operated upon with the convexo-concave Björk-Shiley prosthesis. The 21 mm prosthesis had been inserted in 11 patients and the 23 mm one in the other 11 patients. Left ventricular pump function improved and was normalized in half of the patients. The mean systolic pressure difference across the 21 mm convexo-concave prosthesis was 16.2 +/- 8.1 mmHg at rest and 20.7 +/- 7.9 mmHg during exercise (32 +/- 10 watts). It was 14.9 +/- 6.0 mmHg at rest and 18.6 +/- 6.3 mmHg during exercise (34 +/- 156 watts) across the 23 mm convexo-concave prosthesis. Compared with the earlier investigated standard model Björk-Shiley prosthesis, the 21 mm convexo-concave version creates a lower resistance to blood flow (less than 0.01), whereas no such difference could be demonstrated in the two models of 23 mm tissue diameter. It was concluded that the new convexo-concave tilting disc valve constitutes an improvement over the standard model in the management of the narrow aortic annulus permitting insertion of a 21 mm prosthesis.