SPSS 23 (IBM Corporation, Somer, NY, USA) was used for the analyses. To illustrate the portion of explanted, well-functioning and dysfunctional grafts at the various examination intervals, we modified the statistical techniques recommended by Akins et al. [20]. Aortic valve annulus measurements were converted to age- and body size-dependent Z-scores for DPH and bovine jugular vein patients according to a thesis of W. Berdau (Medical University of Kiel, Germany, 1989). Interpolation lines (Lowess fit) ease the assignment according to the z-value at implantation for subgroups.