title: An Artificial Neural Network Stratifies the Risks of Reintervention and Mortality after Endovascular Aneurysm Repair; a Retrospective Observational study.
abstract: BACKGROUND
  Lifelong surveillance after endovascular repair (EVAR) of abdominal aortic aneurysms (AAA) is considered mandatory to detect potentially life-threatening endograft complications. A minority of patients require reintervention but cannot be predictively identified by existing methods. This study aimed to improve the prediction of endograft complications and mortality, through the application of machine-learning techniques.
  
  
  METHODS
  Patients undergoing EVAR at 2 centres were studied from 2004-2010. Pre-operative aneurysm morphology was quantified and endograft complications were recorded up to 5 years following surgery. An artificial neural networks (ANN) approach was used to predict whether patients would be at low- or high-risk of endograft complications (aortic/limb) or mortality. Centre 1 data were used for training and centre 2 data for validation. ANN performance was assessed by Kaplan-Meier analysis to compare the incidence of aortic complications, limb complications, and mortality; in patients predicted to be low-risk, versus those predicted to be high-risk.
  
  
  RESULTS
  761 patients aged 75 +/- 7 years underwent EVAR. Mean follow-up was 36+/- 20 months. An ANN was created from morphological features including angulation/length/areas/diameters/volume/tortuosity of the aneurysm neck/sac/iliac segments. ANN models predicted endograft complications and mortality with excellent discrimination between a low-risk and high-risk group. In external validation, the 5-year rates of freedom from aortic complications, limb complications and mortality were 95.9% vs 67.9%; 99.3% vs 92.0%; and 87.9% vs 79.3% respectively (p<0.001).
  
  
  CONCLUSIONS
  This study presents ANN models that stratify the 5-year risk of endograft complications or mortality using routinely available pre-operative data.
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, London, SW17 0QT, United Kingdom.
authors.forename: Alan
authors.initials: A
authors.lastname: Karthikesalingam
authors.affiliation: College of Engineering and Applied Science, Aston University, Birmingham, B4 7ET, United Kingdom; Department of Electronics and Communications Engineering, Arab Academy for Science and Technology and Maritime Transport, Alexandria, Egypt.
authors.forename: Omneya
authors.initials: O
authors.lastname: Attallah
authors.affiliation: College of Engineering and Applied Science, Aston University, Birmingham, B4 7ET, United Kingdom.
authors.forename: Xianghong
authors.initials: X
authors.lastname: Ma
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, London, SW17 0QT, United Kingdom.
authors.forename: Sandeep Singh
authors.initials: SS
authors.lastname: Bahia
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, London, SW17 0QT, United Kingdom.
authors.forename: Luke
authors.initials: L
authors.lastname: Thompson
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, London, SW17 0QT, United Kingdom; Department of Community Health Sciences, St George's University of London, London, SW17 0QT, United Kingdom.
authors.forename: Alberto
authors.initials: A
authors.lastname: Vidal-Diez
authors.affiliation: Vascular Surgery Group, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester, LE2 7LX, United Kingdom.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Choke
authors.affiliation: Vascular Surgery Group, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester, LE2 7LX, United Kingdom.
authors.forename: Matt J
authors.initials: MJ
authors.lastname: Bown
authors.affiliation: Vascular Surgery Group, University of Leicester, Robert Kilpatrick Clinical Sciences Building, Leicester Royal Infirmary, Leicester, LE2 7LX, United Kingdom.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Sayers
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, London, SW17 0QT, United Kingdom.
authors.forename: Matt M
authors.initials: MM
authors.lastname: Thompson
authors.affiliation: Department of Outcomes Research, St George's Vascular Institute, London, SW17 0QT, United Kingdom.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Holt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000401:mortality* / Q000601:surgery*; D057510:Endovascular Procedures / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D016571:Neural Networks, Computer; D011183:Postoperative Complications / Q000209:etiology; D019233:Retreatment; D012189:Retrospective Studies; D018570:Risk Assessment