title: Operative mortality rates for intact and ruptured abdominal aortic aneurysms in Michigan: an eleven-year statewide experience.
abstract: OBJECTIVE
  The purposes of this study were (1) to determine the current population-based mortality rate for the surgical treatment of abdominal aortic aneurysms (AAA) in Michigan, (2) to document changes in mortality rates over 11 years, and (3) to identify risk factors for operative mortality.
  
  
  METHODS
  A statewide database provided clinical information on all Michigan hospital admissions with a diagnosis of AAA from 1980 to 1990. The mortality rate analysis included all admissions with a primary diagnosis of AAA that underwent repair. Determination of diagnoses and comorbidities were based on International Classification of Diseases-ninth revision-Clinical Modification codes.
  
  
  RESULTS
  Conventional surgical repairs were performed on 8185 intact and 1829 ruptured AAA. Hospital mortality rates accompanying operation for intact AAA decreased from 13.6% in 1980 to 5.6% in 1990 (p < 0.001). Mortality rates over the 11 years averaged 10.7% in women and 6.8% in men (p < 0.001). Mortality rates averaged 10.7% in 4170 admissions of patients 70 years old or older and 4.2% in 4015 admissions of patients 69 years old or younger. Preexistent kidney failure was associated with an average mortality rate of 41.2% compared with 6.2% without this comorbidity. Preexistent dysrhythmia increased mortality rates from 6.6% to 13.6%. Uncomplicated hypertension, cerebrovascular disease, chronic obstructive pulmonary disease, diabetes, arterial occlusive disease, and ischemic heart disease in recent years were not associated with increased mortality rates. Hospitals with an annual volume of 21 or more intact AAA repairs had a surgical mortality rate of 6.2%, compared with 8.9% in hospitals with lower surgical volume (p < 0.001). Mortality rates for surgical repair of ruptured AAA averaged 49.8% and did not improve significantly over the 11 years studied.
  
  
  CONCLUSIONS
  Despite a dramatic drop in surgical mortality rates, repair of intact AAA remains a formidable undertaking. This population-based series documents a substantially higher mortality rate than most selected series. The unchanged mortality rate for ruptured AAA suggests that development of better algorithms to identify those AAA most apt to rupture and earlier intervention in those instances is likely to improve patient survival rates.
authors.affiliation: Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor.
authors.forename: D J
authors.initials: DJ
authors.lastname: Katz
authors.forename: J C
authors.initials: JC
authors.lastname: Stanley
authors.forename: G B
authors.initials: GB
authors.lastname: Zelenock
mesh_terms: D017677:Age Distribution; D000368:Aged; D017544:Aortic Aneurysm, Abdominal / Q000401:mortality* / Q000601:surgery; D001019:Aortic Rupture / Q000401:mortality* / Q000601:surgery; D016009:Chi-Square Distribution; D005260:Female; D017052:Hospital Mortality / Q000639:trends*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008824:Michigan / Q000453:epidemiology; D008875:Middle Aged; D012307:Risk Factors; D017678:Sex Distribution; D013514:Surgical Procedures, Operative / Q000401:mortality*; D015996:Survival Rate; D013997:Time Factors