Hydrodynamic performance of heart valve prostheses: open discussion on EN ISO 5840

The ‘in vitro’ assessement of hydrodynamic performance of cardiac valve prostheses is regulated by the European Committee for Standardization - International Organization for Standardization (EN ISO) standard 5840, for both steady and unsteady flow conditions. From the engineering point of view, standard prescriptions for the experimental apparatus seem to be not sufficient to avoid misleading evaluation of valve functionality under pulsatile flow. In particular, we here underline that the in vitro estimation of the valvular effective orifice area requires the measurement of the transvalvular pressure drop, but the standard does not specificy neither the geometry of the pulse duplicator in the proximity of pressure measuring sites nor the exact position of the pressure sites. Moreover, following standard prescription, pulsatile experiments must be carried out under a mean aortic pressure of 100 mmHg. However, literature data show that this latter mean pressure usually arises from quite different aortic pressure waveforms. We here underline that not only the mean pressure but pressure waveform as well affects the prosthetic valve performance in ‘in vitro’ tests. From the clinical perspective, the above sources of possible misleading evaluation of prostheses performance might lead to patience-prostesis mismatch, i.e. to hemodynamic performance lower than expected after valve implantation. For these reasons, we encourage an open discussion on possibile improvements of standard prescriptions and prosthetic valve assessment criteria.