MEASURING OUTCOMES - ONE MONTH SURVIVAL AFTER ACUTE MYOCARDIAL-INFARCTION IN SCOTLAND

Objective-To examine 30 day survival after acute myocardial infarction as an outcome indicator, and explore the effects of adjusting for ava ilable prognostic factors such as age, sex, co-morbidity, deprivation, and deaths outside hospital. Design-Cohort study. Setting-The Scottis h Record Linkage System was analysed. This national database Links inp atient data to death certificate information for a population of 5.1 m illion. Subjects-All 40 371 admissions to hospital with a principal di agnosis of acute myocardial infarction, plus all 18 452 deaths outside hospital with a principal cause of death registered as acute myocardi al infarction (ICD9 code 410) during 1988-1991. Main outcome measures- The outcome event was death from any cause, within hospital or elsewhe re, within 30 days of admission. Results-During 1988-1991, 30 day surv ival after acute myocardial infarction was 77% in 40 371 hospital admi ssions, but only 53% when 18 452 acute myocardial infarction deaths in the community were included (a population-based outcome indicator wit h many advantages). Using logistic regression at an individual patient level, the odds of dying within 30 days effectively doubled for each decade of age (odds ratio compared with patients aged under 55: 2.3 ag ed 55-64, 4.4 aged 65-74, 8.2 aged 75-84, 12.0 aged 85 plus); were mar ginally higher in females than in males (odds ratio 1.07); were almost doubled in patients with a history of previous infarction, coronary h eart disease, or other heart disease, and were also significantly incr eased in patients with circulatory disease, respiratory disease, neopl asm, or diabetes. Socioeconomic deprivation had no significant effect. Marked variations in survival between different hospitals and health board areas persisted, even after adjusting for the above prognostic f actors. Conclusion-One month survival after acute myocardial infarctio n could be a useful means of measuring outcome of hospital care. There was important geographical variation in one month survival. These dif ferences could be accounted for by variations in referral, admission, diagnosis, definition, and coding. These variables merit further resea rch and local clinical audit before one month survival after acute myo cardial infarction can be reliably used for detecting differences in q uality of care. In addition, it would be essential to take account of infarct severity.