title: Mortality and morbidity rates after conventional abdominal aortic aneurysm repair.
abstract: OBJECTIVE
  To grade and analyse by levels of evidence the mortality and morbidity rates of elective abdominal aortic aneurysm (AAA) surgery as reported over the past 12 years.
  
  
  METHODS
  Articles on elective AAA surgery published between 1985 and 1996 were retrieved and classified into 5 levels of evidence. Level 1 contains prospective studies and is subdivided into population-based (Level 1a) and hospital-based (Level 1b) studies. Level 2 includes retrospective studies, subdivided into population-based (Level 2a), hospital-based (Level 2b), and hospital-based studies concerning a specified group of selected patients (Level 2c). Operative mortality and systemic and local/vascular complication rates and 95% confidence intervals were calculated per level of evidence.
  
  
  RESULTS
  Seventy-two articles describing a total of 37,654 patients could be included: 2 level 1a studies (patient total: 692), 9 Level 1b studies (patient total: 1,677), 13 Level 2a studies (patient total 21,409), 32 Level 2b studies (patient total: 12,019), and 16 Level 2c studies (patient total: 1,857). The mean 30-day mortality rates of the two population-based levels were similar: 8.2% (6.4%-10.6%) for the prospective (1a) and 7.4% (7.0%-7.7%) for the retrospective series (2a). These figures were significantly higher than the remarkably similar hospital-based mortality rates: 3.8% (3.0%-4.8%) for the prospective (1b), 3.8% (3.5%-4.2%) for the retrospective (2b), and 3.5% (2.8%-4.4%) for selected patient group studies (2c). The most frequent complication was of cardiac origin. In the population-based series the cardiac complication rate was 10.6% (8.5%-13.2%) and 11.1% (9.1%-13.6%) for Levels 1a and 2a respectively. This compared well with the 12.0% (10.5%-13.9%) for the prospective, hospital-based series (Level 1b). The cardiac complication rates in the retrospective, hospital-based studies was significantly lower: 8.9% (8.4%-9.5%) and 6.1% (4.9%-7.6%) for Levels 2b and 2c respectively.
  
  
  CONCLUSIONS
  There is a clear and consistent disagreement in reported mortality rates between hospital-based and population-based studies of elective AAA-surgery. Prospective studies give the best documentation of postoperative morbidity.
authors.affiliation: Department of Surgery, University Medical Center Utrecht, The Netherlands. j.d.blankensteijn chir.azu.nl.
authors.forename: J D
authors.initials: JD
authors.lastname: Blankensteijn
mesh_terms: D017544:Aortic Aneurysm, Abdominal / Q000401:mortality* / Q000601:surgery; D017052:Hospital Mortality; D006801:Humans; D015994:Incidence; D007431:Intraoperative Complications / Q000453:epidemiology; D011183:Postoperative Complications / Q000453:epidemiology*; D011446:Prospective Studies; D012189:Retrospective Studies; D015996:Survival Rate; D014656:Vascular Surgical Procedures / Q000401:mortality*