OBJECTIVE To assess the influence of diabetes on long term prognosis after reperfusion treatment and its interaction with multivessel disease.

DESIGN A retrospective observational study.

SETTING Hiroshima City Hospital.

PATIENTS 1660 consecutive patients with acute myocardial infarction who underwent coronary angiography within 24 hours after the onset of chest pain.

MAIN OUTCOME MEASURES Influence of diabetes on 10 year survival after infarction was assessed using the generalised Wilcoxon test and Cox's proportional hazards regression. Follow up was completed in 1622 patients (98%).

RESULTS Diabetic patients had more multivessel disease than non-diabetic patients (53%v 34%, p < 0.001). When only patients with single vessel disease were compared, diabetes was associated with a reduced 10 year survival after infarction (p = 0.002). On the other hand, in patients with multivessel disease there was no significant difference in survival between diabetic and non-diabetic patients (p = 0.70). Multivariate analysis also showed that diabetes was an independent risk factor related to 10 year mortality after infarction in patients with single vessel disease (odds ratio (OR) 1.81, 95% confidence interval (CI) 1.27 to 2.54; p = 0.001) and not in patients with multivessel disease (OR 1.17, 95% CI 0.85 to 1.60; p = 0.34).

CONCLUSIONS Diabetes is an independent predictor of long term mortality after infarction in patients with single vessel disease. However, in the presence of multivessel disease, prognosis after infarction is impaired regardless of diabetes, and the influence of diabetes is less obvious.