番茄社区

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SAN FRANCISCO -- Sapien 3 transcatheter aortic valves will probably last 25 years when implanted right, bench testing showed.

After 1 billion cycles of accelerated wear testing with a pulsatile flow system -- simulating 25 years of wear-and-tear in the heart in just 30 months -- the TAVR valve showed "excellent" durability, John Webb, MD, of St. Paul's Hospital in Vancouver, and colleagues found.

Leaflet condition and hemodynamics were similar to a Magna Ease surgical valve tested the same way, they ahead of a presentation here at the Transcatheter Cardiovascular Therapeutics meeting.

With poorer implantation characteristics, the valves looked good for 5 years of simulated wear (200 million cycles).

"As transcatheter aortic valve replacement expands to lower risk patients, durability will be of increasing importance," they wrote.

Julinda Mehilli, MD, of the German Centre for Cardiovascular Research in Munich, agreed in , noting that current available clinical evidence shows 85% freedom from structural valve deterioration at around 8 years post-implantation.

As important as this additional information is, there were some key limitations, she cautioned: Transvalvular gradient, its change over time, and leaflet closing velocity were not reported in the study. Also, the study used saline as the fluid instead of a saline-glycerine mix that more closely mimics the viscosity of blood. And it would have been better to have 25-year simulation data for non-nominally implanted valves.

"Modern hydrodynamic testing protocols in addition to platelet activation testing are required to more fully evaluate transcatheter bioprostheses durability," Mehilli wrote.

The study implanted the valves in a physiologic model of the aorta and annulus, including transit over an aortic arch, with all the dilation and other expansion as typical in a clinical case. Serial hydrodynamic testing and visual inspection for leaflet damage was done over the 30 months of testing, looking at both transvalvular regurgitant fraction and effective orifice area as a mode of failure.

At the equivalent of 25-years use, average regurgitant fractions for the 20-, 23-, 26-, and 29-mm Sapien 3 valves were 0.92%, 1.29%, 1.73%, and 2.47%, respectively.

Average regurgitant fractions for the respective valve sizes in over-expanded deployment were 4.36%, 7.68%, 6.80%, and 9.00%. In under-expanded scenarios, these were 3.06%, 4.46%, 7.72%, and 8.65%; and in elliptical implantation scenarios they were 3.30%, 6.13%, 6.77%, and 8.72%.

For the surgical valve, averaged regurgitant fractions at 1 billion cycles for the 21-, 23-, 27-, and 29-mm Magna Ease were 0.69%, 1.29%, 1.52%, and 2.75%, respectively.

Minor abrasions and delamination were seen with both types of valves but without compromising the function of the valve. "All samples had similar wear across the leaflets," the researchers noted.

They acknowledged that they couldn't determine long-term leaflet calcification or thrombogenicity. That will probably have to await 25 actual years of evaluation.