Comparison of intraoperative flow measurements and haemodynamic findings at follow-up in patients with different aortic disc valve prostheses.

Intraoperative as well as postoperative assessment of effective orifice area, determined by relating flow through a prosthetic heart valve to the pressure gradient measured across the valve, provides a data base for comparison of different types of cardiac prostheses. As a measure of valve performance, we have used the derivation of both the effective area according to the Aaslid formula measured intraoperatively and to the Gorlin formula measured at a re-catheterization study. We also established the parameter 'effective index area', Ia or Ii. Ia is defined as the ratio between the effective orifice area and the annulus orifice area, and Ii as the ratio between the effective orifice area and the internal orifice area of the valve housing. The patients included in the study had either Lillehei-Kaster, Björk-Shiley or Hall-Kaster aortic valve prostheses inserted. In most of the Lillehei-Kaster prostheses, Ia varied around 0.27 and Ii around 0.56, while the corresponding values in the Björk-Shiley prostheses were 0.35 and 0.56, increasing to around 0.50 and 0.75 respectively in the Hall-Kaster prostheses.