Newly detected abnormal glucose regulation and long-term prognosis after acute myocardial infarction: Comparison of an oral glucose tolerance test and glycosylated haemoglobin A1c

Background: An oral glucose tolerance test (OGTT) and/or glycosylated haemoglobin A1c (HbA1c) in patients with acute myocardial infarction (AMI) identify patients with increased mortality risk, but no comparison of the long-term prognostic values has yet been investigated.

Methods: This study was a prospective cohort enrolling patients with AMI between 2002 until 2008 and follow-up until 1st October, 2012. Patients without known diabetes mellitus (DM) underwent an OGTT. Seventy-nine patients with known DM did not have an OGTT performed. Primary endpoint was all-cause mortality. We included 548 patients with AMI, of whom 469 underwent a standardized OGTT and were stratified according to OGTT and HbA1c.

Results: During 9.8years of follow-up, 179 (33%) patients died. In patients having increased HbA1c ≥6.5%, a significantly increased mortality was observed (Hazard Ratio (HR) 1.60 [1.09-2.34]). However, when adjusting for known DM, no significance was detected. An OGTT did not show a significantly increased mortality, if used separately. A combined estimate showed a significantly increased mortality in patients categorized as newly diagnosed DM by OGTT and HbA1c<6.5% (HR 1.56 [95% CI 1.07-2.30]) compared to patients categorized as normal/impaired fasting glycaemia/impaired glucose tolerance by OGTT and HbA1c <6.5%. Approximately 50% of the patients with newly diagnosed DM by OGTT were only detected due to 2-hour post-load glucose values.

Conclusion: An OGTT is recommended in AMI patients without known DM and HbA1c<6.5%. Patients categorized as newly diagnosed DM by OGTT although HbA1c <6.5% share the same high risk of mortality as patients with HbA1c≥6.5%.