title: Vascular Response to Experimental Stent Malapposition and Under-Expansion.
abstract: Up to 80% of all endovascular stents have malapposed struts, and while some impose catastrophic events others are inconsequential. Thirteen stents were implanted in coronary arteries of seven healthy Yorkshire pigs, using specially-designed cuffed balloons inducing controlled stent malapposition and under-expansion. Optical coherence tomography (OCT) imaging confirmed that 25% of struts were malapposed (strut-wall distance <strut thickness) to variable extent (max. strut-wall distance malapposed group 0.51 ± 0.05 mm vs. apposed group 0.09 ± 0.05 mm, p = 2e-3). Imaging at follow-up revealed malapposition acutely resolved (<1% of struts remained malapposed at day 5), with strong correlation between lumen and the stent cross-sectional areas (slope = 0.86, p < 0.0001, R (2) = 0.94). OCT in three of the most significantly malapposed vessels at baseline showed high correlation of elastic lamina area and lumen area (R (2) = 0.96) suggesting all lumen loss was related to contraction of elastic lamina with negligible plaque/intimal hyperplasia growth. Simulation showed this vascular recoil could be partially explained by the non-uniform strain environment created from sub-optimal expansion of device and balloon, and the inability of stent support in the malapposed region to resist recoil. Malapposition as a result of stent under-expansion is resolved acutely in healthy normal arteries, suggesting existing animal models are limited in replicating clinically observed persistent stent malapposition.
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA. ccob@mit.edu.
authors.forename: Caroline C
authors.initials: CC
authors.lastname: O'Brien
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA.
authors.forename: Augusto C
authors.initials: AC
authors.lastname: Lopes
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA.|Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Kumaran
authors.initials: K
authors.lastname: Kolandaivelu
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA.
authors.forename: Mie
authors.initials: M
authors.lastname: Kunio
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Brown
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA.|Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.|Charles Stark Draper Laboratory, 555 Technology Square, Cambridge, MA, USA.
authors.forename: Vijaya B
authors.initials: VB
authors.lastname: Kolachalama
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA.
authors.forename: Claire
authors.initials: C
authors.lastname: Conway
authors.affiliation: CBSET, Lexington, MA, USA.
authors.forename: Lynn
authors.initials: L
authors.lastname: Bailey
authors.affiliation: CBSET, Lexington, MA, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Markham
authors.affiliation: University Hospitals, Cleveland, OH, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Costa
authors.affiliation: Harvard School of Public Health, Boston, MA, USA.
authors.forename: James
authors.initials: J
authors.lastname: Ware
authors.affiliation: Institute of Medical Engineering and Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, E25-449, Cambridge, MA, 02139, USA.|Cardiovascular Division, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA.
authors.forename: Elazer R
authors.initials: ER
authors.lastname: Edelman
mesh_terms: D000818:Animals; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology; D004548:Elasticity; D008955:Models, Cardiovascular; D062645:Percutaneous Coronary Intervention / Q000009:adverse effects*; D015607:Stents / Q000009:adverse effects*; D013552:Swine; D041623:Tomography, Optical Coherence
keywords: Malapposition; Optical coherence tomography; Pre-clinical model; Stent; Stent under-expansion