title: Bioabsorbable vascular scaffold overexpansion: insights from in vitro post-expansion experiments.
abstract: While bioresorbable vascular scaffolds (BVS) are increasingly used in clinical practice, their behaviour when post-dilated beyond their recommended maximum overexpansion diameter remains sparsely documented. We aimed to test the overexpansion of the BVS scaffold in vitro and evaluate the impact of excessive scaffold oversizing on focal point support.
  
  
  
  We examined the post-expansion behaviour of the bioresorbable vascular scaffold (3.0 mm and 3.5 mm Absorb BVS; Abbott Vascular, Santa Clara, CA, USA) after overexpansion with non-compliant (NC) balloons of increasing diameters. After each oversizing step, the scaffolds were measured and inspected for strut disruption using microscope and optical coherence tomography imaging. Point force mechanical measurements on single scaffold struts were also performed to evaluate the impact of excessive scaffold overstretching on focal mechanical support. 3.0 mm and 3.5 mm scaffold sizes could be post-expanded up to 1 mm above their nominal diameters without any strut fracture when deployed without an external constraining model. Importantly, when overexpansion of both scaffold sizes was repeated using a constraining silicone lesion model, only post-expansion with an NC balloon size 0.5 mm larger than the scaffold nominal sizes could be performed without strut fractures. Point force compression analysis on single struts shows that overstretched struts with fractures provided lower focal strength compared to overexpanded ring segments without fractures and normal segments expanded at nominal pressure.
  
  
  
  In our experiments, only overexpansion with an NC balloon 0.5 mm larger than the BVS size was feasible for BVS deployed inside an arterial lesion model. Overexpansion of the BVS scaffold beyond recommended post-dilation limits can lead to strut disconnections and focal loss of mechanical support.
authors.affiliation: National Heart Centre Singapore, Singapore.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Foin
authors.forename: Renick
authors.initials: R
authors.lastname: Lee
authors.forename: Alessio
authors.initials: A
authors.lastname: Mattesini
authors.forename: Gianluca
authors.initials: G
authors.lastname: Caiazzo
authors.forename: Enrico
authors.initials: E
authors.lastname: Fabris
authors.forename: Ismail Dogu
authors.initials: ID
authors.lastname: Kilic
authors.forename: Jing Ni
authors.initials: JN
authors.lastname: Chan
authors.forename: Yingying
authors.initials: Y
authors.lastname: Huang
authors.forename: Subbu S
authors.initials: SS
authors.lastname: Venkatraman
authors.forename: Carlo
authors.initials: C
authors.lastname: Di Mario
authors.forename: Philip
authors.initials: P
authors.lastname: Wong
authors.forename: Holger
authors.initials: H
authors.lastname: Nef
mesh_terms: D020341:Absorbable Implants; D015906:Angioplasty, Balloon, Coronary / Q000009:adverse effects / Q000295:instrumentation*; D062906:Cardiac Catheters; D019544:Equipment Failure Analysis; D008422:Materials Testing; D008953:Models, Anatomic; D008955:Models, Cardiovascular; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012828:Silicones; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D012828:Silicones