Doppler-derived pressure differences in normally functioning aortic valve prostheses. Studies in Björk-Shiley...

To determine the normal range of maximum and mean Doppler-derived pressure differences for mechanical and bioprosthetic valves in the aortic position, Doppler echocardiography was performed on 239 stable patients with normally functioning Björk-Shiley monostrut (BSM, n = 185) or Biocor porcine (n = 54) prostheses. The interval from aortic valve replacement to echocardiography was 3-9 days. Maximum and mean pressure differences were significantly greater in 21 mm than in 25 or 27 mm BSM prostheses. The pressure differences in 23 mm BSM valves did not diverge significantly from those in 21, 25 or 27 mm valves. The mean pressure difference did not exceed 30 mm Hg in any type or size of studied prosthesis. No significant differences were found in pressure gradients in comparisons between BSM and Biocor prostheses of corresponding sizes. The calculated velocity ratio for BSM prostheses was not significantly influenced by the valve size. We suggest that the normal range of Doppler-derived maximum and mean pressure differences determined in this study be adopted as reference in evaluations of aortic BSM and Biocor valve prostheses.