In-vitro measurements of the regurgitation of mechanical mitral heart valve prostheses in case of atrial fibrillation

Background and aim of the study: The characterization of heart valve prosth eses requires regurgitation tests to be conducted in pulsatile flow. Althou gh tests are generally conducted in accordance with hemodynamic conditions of a healthy young man, heart valve implantation is often associated with o ther pathology, such as atrial fibrillation. To run more realistic trials, four mechanical heart valve prostheses were tested with, and then without, atrial contraction. Methods: The dual activation simulator (DAS) allow simulation of physiologi cally normal and pathological flows through the mitral valve. The DAS compr ises silicon-based cavities, is activated by pumps, and was equipped succes sively with monoleaflet (Bjork-Shiley, Medtronic Hall) and bileaflet (St. J ude Medical, CarboMedics) valves. Each valve (mitral, size 27 mm) was teste d under two conditions (with and without atrial contraction) at a mean flow rate of 3 l/min of glycerol/water solution (analog blood viscosity). Results: Leakage volumes were of the same magnitude as the precision of the instruments. Respectively, closing volumes increased from normal condition s to atrial fibrillation from 3.2 to 5.1 ml for Bjork-Shiley, from 4.6 to 6 .3 ml for Medtronic Hall, from 5 to 6.6 ml for St. Jude Medical, and from 5 .2 to 5.4 ml for CarboMedics. The standard deviation was below the precisio n of measurements (+/-0.5 ml). Conclusion: Without atrial contraction, the valves seemed to be closed by b ackward flow only, thus confirming earlier reports. This study showed that different heart valves behave differently in pathological situations with r egard to their design; this must be considered when selecting a valve for i mplantation.