S Hamed Alavi1, Elliott M Groves2, Arash Kheradvar3. 1. The Edwards Lifesciences Center for Advanced Cardiovascular Technology, Department Biomedical Engineering, University of California, Irvine, Irvine, California. 2. The Edwards Lifesciences Center for Advanced Cardiovascular Technology, Department Biomedical Engineering, University of California, Irvine, Irvine, California; Division of Cardiology, University of California, Irvine, Irvine, California. 3. The Edwards Lifesciences Center for Advanced Cardiovascular Technology, Department Biomedical Engineering, University of California, Irvine, Irvine, California; Division of Cardiology, University of California, Irvine, Irvine, California. Electronic address: arashkh@uci.edu.
Abstract
BACKGROUND: Transcatheter aortic valve replacement has emerged as a promising therapy for treatment of severe aortic stenosis. Although it has been shown that these valves can be safely delivered and implanted, studies of valve longevity are lacking because of the infancy of the technology. Particularly, the effects of stent crimping on the valve's leaflets have not yet been sufficiently investigated. In this study, we have characterized the effects of crimping on pericardial leaflets in time and through the depth of the tissue. METHODS: To test the structural changes at the surface and deep layers of bovine pericardial leaflets, scanning electron microscopy and second-harmonic generation microscopy were used. An uncrimped tissue sample was imaged, followed by imaging a segment of tissue after crimping in a stented transcatheter valve, immediately after, at 20 minutes, and 60 minutes after crimping. The crimping experiment was performed for multiple crimping sizes (ie, 14F, 16F, and 18F). We defined a damage index that quantifies the level of leaflet structural changes as a result of crimping. RESULTS: Based on the calculated damage indices and analyses of the raw images, it was determined that crimping does measurable damage to the leaflet tissue that persists with time. CONCLUSIONS: Significant tissue damage was observed at the surface layers of the leaflets. In the deeper tissue layers, damage was substantial for 14F crimping; however, it became less significant but still visible for larger collapse profiles. Crimping may induce substantial structural damage to pericardial leaflets that does not improve with time.
BACKGROUND: Transcatheter aortic valve replacement has emerged as a promising therapy for treatment of severe aortic stenosis. Although it has been shown that these valves can be safely delivered and implanted, studies of valve longevity are lacking because of the infancy of the technology. Particularly, the effects of stent crimping on the valve's leaflets have not yet been sufficiently investigated. In this study, we have characterized the effects of crimping on pericardial leaflets in time and through the depth of the tissue. METHODS: To test the structural changes at the surface and deep layers of bovine pericardial leaflets, scanning electron microscopy and second-harmonic generation microscopy were used. An uncrimped tissue sample was imaged, followed by imaging a segment of tissue after crimping in a stented transcatheter valve, immediately after, at 20 minutes, and 60 minutes after crimping. The crimping experiment was performed for multiple crimping sizes (ie, 14F, 16F, and 18F). We defined a damage index that quantifies the level of leaflet structural changes as a result of crimping. RESULTS: Based on the calculated damage indices and analyses of the raw images, it was determined that crimping does measurable damage to the leaflet tissue that persists with time. CONCLUSIONS: Significant tissue damage was observed at the surface layers of the leaflets. In the deeper tissue layers, damage was substantial for 14F crimping; however, it became less significant but still visible for larger collapse profiles. Crimping may induce substantial structural damage to pericardial leaflets that does not improve with time.
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