Study of the influence of the flow conditions on valvular prostheses  regurgitation   Among the in vitro tests for the qualifying of a valvular prosthesis, the study of regurgitation accounts for a large part. The ratio of regurgitation is defined as the volume of fluid which flows backwards through the valve during a cardiac cycle, expressed as a percentage of the ejected volume. The volume of regurgitation is the sum of the closing volume ( ebbing when the valve is closing - purple) and of the leakage volume (ebbing through the closed valve - blue). Volumes of regurgitation are displayed on figure 11. While the leakage volume, proper to each valve, remains unchanged when modifying the conditions, the closing volume is significantly different for the two valves between the normal conditions and the atrial fibrillation conditions. This changing is due to to the modification of the flow dynamics, which commands the cinematic of the valve. This also proves that valves' efficiency decreases in this pathological case. We thus confirm the necessity of studying real physiologic conditions in the qualification of a new valve. Regurgitation volume for various cardiac prostheses.