OPERATIVE MORTALITY-RATES FOR INTACT AND RUPTURED ABDOMINAL AORTIC-ANEURYSMS IN MICHIGAN - AN 11-YEAR STATEWIDE EXPERIENCE

Purpose: The purposes of this study were (1) to determine the current population-based mortality rate for the surgical treatment of abdomina l aortic aneurysms (AAA) in Michigan, (2) to document changes in morta lity rates over 11 years, and (3) to identify risk factors for operati ve mortality. Methods: A statewide database provided clinical informat ion on all Michigan hospital admissions with a diagnosis of AAA from 1 980 to 1990. The mortality rate analysis included all admissions with a primary diagnosis of AAA that underwent repair. Determination of dia gnoses and comorbidities were based on International Classification of Diseases-ninth revision-Clinical Modification codes. Results: Convent ional surgical repairs were performed on 8185 intact and 1829 ruptured AAA. Hospital mortality rates accompanying operation for intact AAA d ecreased from 13.6% in 1980 to 5.6% in 1990 (p < 0.001). Mortality rat es over the 11 years averaged 10.7% in women and 6.8% in men (p < 0.00 1). Mortality rates averaged 10.7% in 4170 admissions of patients 70 y ears 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 obstructi ve pulmonary disease, diabetes, arterial occlusive disease, and ischem ic heart disease in recent years were not associated with increased mo rtality rates. Hospitals with an annual volume of 21 or more intact AA A 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 si gnificantly over the 11 years studied. Conclusion: Despite a dramatic drop in surgical mortality rates, repair of intact AAA remains a formi dable undertaking. This population-based series documents a substantia lly higher mortality rate than most selected series. The unchanged mor tality rate for ruptured AAA suggests that development of better algor ithms to identify those AAA most apt to rupture and earlier interventi on in those instances is likely to improve patient survival rates.