With their extensive work on patient–prosthesis mismatch (PPM) Drs Dumesnil and Pibarot have greatly increased our attentiveness about the potential harm caused by small sizing of a prosthetic heart valve. Following these important studies, numerous groups from all over the world have investigated the impact of moderate and severe PPM on mortality. However, results have been controversial, particularly for moderate mismatch. Some indicated a strong influence of PPM on mortality while others could not show such an effect. Even in the case of impaired left ventricular function, results were not consistent. While it was shown by a Canadian trial1 that even moderate PPM strongly influences early mortality after aortic valve replacement in patients with impaired left ventricular …