Sizing strategy is a major determinant of postoperative pressure gradients in commonly implanted stented tissue valves.

Objective: We compared the haemodynamic performance of two pericardial aortic prostheses with the stent either on the outside (Perimount), or the inside (Mitroflow) of the valve cusps, with regard to sizing strategies and valve dimensions.

Methods: We analysed discharge echoes from all patients who received an isolated Perimount (n = 537) or Mitroflow (n = 164) between January 2007 and November 2010. We obtained outer valve diameters from the manufacturers, and measured sizer dimensions.