Insulin-sensitizing antihyperglycemic drugs and mortality after acute myocardial infarction: insights from the National Heart Care Project.

OBJECTIVE Thiazolidinediones (TZDs) and metformin are insulin-sensitizing antihyperglycemic agents with reported benefits on atherosclerosis. Despite extensive use in patients with diabetes and cardiovascular disease, there is a paucity of outcomes data with metformin and none yet with TZDs. We sought to determine the impact of these insulin sensitizers on outcomes in diabetic patients after hospitalization with acute myocardial infarction (AMI). RESEARCH DESIGN AND METHODS We conducted a retrospective cohort study of 24,953 Medicare beneficiaries with diabetes discharged after hospitalization with AMI between April 1998 and March 1999 or July 2000 and June 2001. The independent association between discharge prescription for metformin, TZD, or both agents and outcomes at 1 year was assessed in multivariable Cox proportional hazards models, adjusting for patient, physician, and hospital variables. The primary outcome was time to death within 1 year of discharge; secondary outcomes were time to first rehospitalization within 1 year of discharge for AMI, heart failure, and all causes. RESULTS There were 8,872 patients discharged on an antihyperglycemic agent, of which 819 were prescribed a TZD, 1,273 metformin, and 139 both drugs. After multivariable analysis, compared with patients prescribed an antihyperglycemic regimen that included no insulin sensitizer, mortality rates were not significantly different in patients treated with either metformin (hazard ratio [HR] 0.92 [95% CI 0.81-1.06]) or a TZD (0.92 [0.80-1.05]) but were lower in those prescribed both drugs (0.52 [0.34-0.82]). The results were similar among patients with heart failure. The prescription of a TZD was associated with a borderline higher risk of all-cause readmission (1.09[1.00-1.20]), predominately due to a higher risk for heart failure readmission (1.17 [1.05-1.30]). CONCLUSIONS Individually, prescription of insulin-sensitizing drugs is not associated with a significantly different risk of death in older diabetic patients within 1 year following AMI compared with other antihyperglycemic agents. Combined, however, metformin and TZDs may exert benefit. TZD prescription is associated with a higher risk of readmission for heart failure after myocardial infarction.