title: Predictive value of negative initial postoperative imaging after endovascular aortic aneurysm repair.
abstract: OBJECTIVE
  The risk of endoleak and reintervention after endovascular abdominal aortic aneurysm repair necessitates lifelong surveillance, which has associated costs, radiation exposure, and risk of nephrotoxicity. The best imaging method and timing of surveillance remain controversial. We sought to determine if a negative result of first postoperative imaging by computed tomography (CT) scan was predictive of decreased need for reintervention. We hypothesized that initial negative postoperative imaging could identify a low-risk cohort of patients who could be observed less frequently.
  
  
  METHODS
  Retrospective review of prospectively collected institutional outcomes data (2004-2009) included stratification according to postoperative imaging results. Baseline characteristics and aneurysm morphology were compared between the two groups. Cox regression analysis was used to identify risk factors predictive for endoleak-related reintervention. Kaplan-Meier survival curves were used to plot freedom from all-cause reintervention and endoleak-related reintervention for the two groups.
  
  
  RESULTS
  A total of 134 patients were included in the analysis. A total of 107 patients (80%) had negative initial postoperative imaging, whereas 27 patients (20%) had evidence of an endoleak. There were no significant differences between the two groups in terms of comorbidities or anticoagulation status. Kaplan-Meier survival curves showed that there was a significant difference between those patients who had a negative initial CT scan and those who had a positive scan for endoleak in terms of both overall reintervention rates and leak-related reintervention rates. Endoleak on the first postoperative CT scan was associated with a hazard ratio of 6.37 (confidence interval, 2.02-20.10; P = .002) for leak-related reintervention and a hazard ratio of 6.01 (confidence interval, 2.24-16.17; P < .001) for all-cause reintervention.
  
  
  CONCLUSIONS
  Patients with negative initial postoperative imaging were significantly less likely to require repeated interventions. These data suggest that these patients are candidates for less rigorous screening protocols.
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Heather L
authors.initials: HL
authors.lastname: Gill
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Ladowski
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Monisha
authors.initials: M
authors.lastname: Sudarshan
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Kent S
authors.initials: KS
authors.lastname: Mackenzie
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Marc M
authors.initials: MM
authors.lastname: Corriveau
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Cherrie Z
authors.initials: CZ
authors.lastname: Abraham
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada.
authors.forename: Daniel I
authors.initials: DI
authors.lastname: Obrand
authors.affiliation: Division of Vascular Surgery, McGill University Health Centre, Montreal, Quebec, Canada. Electronic address: oren.steinmetz@muhc.mcgill.ca.
authors.forename: Oren K
authors.initials: OK
authors.lastname: Steinmetz
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging / Q000601:surgery*; D001027:Aortography / Q000379:methods*; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects* / Q000295:instrumentation; D016009:Chi-Square Distribution; D057867:Endoleak / Q000000981:diagnostic imaging* / Q000209:etiology / Q000601:surgery; D057510:Endovascular Procedures / Q000009:adverse effects* / Q000295:instrumentation; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D012086:Reoperation; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D015607:Stents; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome