The article by Cleveland and colleagues [1Cleveland J.D. Bowdish M.E. Eberhardt C.E. et al.Evaluation of hemodynamic performance of aortic valve bioprostheses in a model of oversizing.Ann Thorac Surg. 2017; 103: 1866-1877Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar] provides a fascinating insight in to the interaction between the dynamics of the left ventricular outflow tract and an implanted tissue prosthetic heart valve. Not only does it shed new light on the interaction between the left ventricular outflow tract and the aortic root; it shakes some of the tenets of surgical practice and of heart valve design. The conventional wisdom is that the bigger the prosthesis, the better the hemodynamics will be, but the authors have shown that this is not necessarily the case. They have neatly demonstrated that the optimal relationship between the implanted prosthesis and the outflow tract is one in which the sizes of the two are equally matched. In simple terms, if the diameter of the outflow tract can be seen through the implanted prosthesis to be smaller than the prosthesis, then there is the potential that the valve leaflets will not open fully with consequent reduction in the effective orifice area. In surgical terms, this is probably best achieved by using a supra-annular valve or simple interrupted sutures for implantation, and of course by avoiding deliberate oversizing. There are also potential implications for heart valve manufacturers. The development of pericardial valves where the pericardium is placed outside the frame of the valve would seem at face value to be a logical way of improving the effective orifice area. However, these prostheses already incorporate a degree of oversizing in their design, and they may more prone to the effects demonstrated in this article than conventionally designed valves with the frame outside are. Although the authors have exaggerated to make their point—implanting a prosthesis three sizes bigger than the measured annulus is not practicable surgically—and this should make surgeons think carefully about both valve sizing and implantation technique. They are to be congratulated on their work. The challenge now is to demonstrate whether this phenomenon is seen in patients, or whether the tendency for these increased gradients to develop can be eliminated in the design process. Evaluation of Hemodynamic Performance of Aortic Valve Bioprostheses in a Model of OversizingThe Annals of Thoracic SurgeryVol. 103Issue 6PreviewThe risk of patient–prosthesis mismatch drives most surgeons to select the largest bioprosthesis possible during aortic valve replacement, but interactions between the native aortic annulus and valve prosthesis remain poorly defined. We examined the hemodynamic and functional consequences of oversizing contemporary bioprostheses in an in vitro model. Full-Text PDF