title: Geometrical and stress analysis of factors associated with stent fracture after melody percutaneous pulmonary valve implantation.
abstract: BACKGROUND
  Patients treated with the Melody device (Medtronic) for percutaneous pulmonary valve implantation experience stent fractures in ≈25% of the cases. The aim of this study is to identify the risk factors associated with fracture using 3-dimensional (3D) analyses.
  
  
  RESULTS
  In situ 3D shape of the Melody stent was reconstructed from 42 patients using procedural biplane fluoroscopy images, after balloon inflation, at systole and diastole. Four geometric parameters at systole and their variation during balloon deflation and cardiac cycles were measured to describe the 3D strut, cell, section, and stent configuration. Furthermore, patient-specific computer simulations were set up to replicate the history of stent deformations for each patient. Maximum and minimum principal stresses resulting from these analyses were monitored during balloon deflation and cardiac cycle. Univariate logistic regression analyses of 21 geometric parameters and of 4 stress parameters respectively, identified the decreased stent circularity after balloon deflation (odds ratio 0.98; 95% confidence interval, 0.96-0.99; P=0.006) and large compressive stresses during balloon deflation (odds ratio, 0.98; 0.96-0.997; P=0.03), as associated with the risk of fracture. In a multivariable logistic regression model, the 2 covariates identified on univariate analysis (1 geometric and 1 stress) were found to be independently associated with the risk of fracture. The resultant statistical model correctly identified fracture/no fracture in 93% of patients.
  
  
  CONCLUSIONS
  Changes in stent section shape after balloon deflation are important variables influencing fracture. This methodology could help design tailored follow-up for patients after percutaneous pulmonary valve implantation.
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.).
authors.forename: Daria
authors.initials: D
authors.lastname: Cosentino
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.).
authors.forename: Michael A
authors.initials: MA
authors.lastname: Quail
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.).
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Pennati
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.).
authors.forename: Claudio
authors.initials: C
authors.lastname: Capelli
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.).
authors.forename: Philipp
authors.initials: P
authors.lastname: Bonhoeffer
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.).
authors.forename: Vanessa
authors.initials: V
authors.lastname: Díaz-Zuccarini
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.).
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Taylor
authors.affiliation: From the Department of Mechanical Engineering (D.C., V.D.-Z.), Institute of Cardiovascular Science and Great Ormond Street Hospital for Children (D.C., M.A.Q., C.C., A.M.T., S.S.), University College London, London, United Kingdom; Department of Chemical Engineering, Politecnico di Milano, Milan, Italy (G.P.); and Fondazione G. Monasterio, CNR-Regione Toscana, Pisa, Italy (P.B.). s.schievano@ucl.ac.uk.
authors.forename: Silvia
authors.initials: S
authors.lastname: Schievano
mesh_terms: D000279:Administration, Cutaneous; D000293:Adolescent; D000328:Adult; D019917:Blood Vessel Prosthesis Implantation; D002648:Child; D003198:Computer Simulation; D019544:Equipment Failure Analysis; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D057285:Precision Medicine; D011475:Prosthesis Failure / Q000209:etiology; D011664:Pulmonary Valve / Q000473:pathology / Q000601:surgery*; D011665:Pulmonary Valve Insufficiency / Q000175:diagnosis* / Q000601:surgery; D012307:Risk Factors; D015607:Stents / Q000706:statistics & numerical data; D013314:Stress, Mechanical; D055815:Young Adult
keywords: finite element analysis; pulmonary valve; stent