Is Leaflet Fluttering of Biological Aortic Valve Substitutes during Systole a Desired Effect or a Hemodynamic Problem?

Objectives: The fluttering of leaflets of a native aortic valve as well as biological valve substitutes is regularly observed in in-vitro studies utilizing high-speed camera assessment and in in-vivo studies visualized by means of echocardiography as well. The phenomenon is not yet fully understood. At present, it is unclear as to whether it should be addressed as an adverse or a beneficial behavior. We investigated this phenomenon in an in vitro study.

Methods: Different biological valves of three different sizes were analyzed in a pulse duplicator (cardiac output 3.5–8.4 l/min). Edwards Perimount Magna (EP), Medtronic Mosaic (MM), Sorin Mitroflow (SM), Edwards Sapien (ES), and Medtronic Evolut (ME) were investigated. The two latter ones before and after crimping. Testfluids were saline, glycerin-water-mixture and praestol. Mean transvalvular gradients were measured. Function of all valves was visualized by means of a high-speed camera at 1000 frames/sec. The films were analyzed by a newly developed software calculating the extent of fluttering by analyzing the involved area as well as the amplitude of the fluttering edges. Thus, quantification could be achieved.

Results: Leaflet fluttering depends on valve type, size, and extrinsic factors like test solution and hemodynamic parameters. In generally valve substitutes with cusps from pericardium showed a reduced fluttering effect compared with native cusps. After crimping valves also presented a reduced cusp movement.

Conclusion: We hypothesize that leaflet fluttering transfers energy from aortic valve leaflets into the bloodstream thereby reducing stress and burden on the leaflets microstructure and this behavior has been evolutionary developed over millions of years in tricuspid valves because it improves long-term function. Crimping of a biological valve substitute to prepare it for catheter based implantation (TAVI) can damage the microstructure of the leaflets and may thus provoke premature degeneration. The extent of leaflet fluttering may thus serve as an indicator for an uncompromised behavior and a reduction of it may be used to detect damage to the microstructure of the fibrous apparatus due to crimping.