Does glucose level at hospital discharge predict one-year mortality in patients with diabetes mellitus treated with percutaneous coronary intervention for ST-segment elevation myocardial infarction?

Background: It has been shown that diabetes mellitus (DM) is an independent prognostic factor in patients with myocardial infarction (MI). In addition to that fact the prognostic significance of blood glucose (BG) abnormalities in the acute phase of MI has also been suggested. Recently, a new prognostic factor has been evaluated - the glucose level at hospital discharge.
Aim: To assess whether the glucose level at hospital discharge is associated with one-year mortality in patients with DM treated with percutaneous coronary intervention (PCI) for ST-segment elevation MI (STEMI), taking into account hypoglycaemic treatment.
Methods: Consecutive patients with STEMI and DM treated with PCI, who survived hospitalisation, were included in the analysis. Patients were assumed to have DM if previous diagnosis of DM or newly diagnosed DM during hospital stay was noted. Criteria of newly diagnosed DM were as follows: fasting BG >or=7 mmol/l at least twice after acute phase of STEMI, BG >or=11.1 mmol/l in a 2-hour glucose tolerance test performed before discharge. Fasting plasma glucose at hospital discharge was used for analysis.
Results: Out of 2762 consecutive patients with STEMI, 565 had DM. In-hospital mortality in this group was 9.4% (53 patients), so the final DM group consisted of 512 patients. After discharge 59 (11.5%) patients died during one-year follow-up. The glucose level at discharge was not an independent prognostic factor of one-year mortality in the whole analysed group, however insulin treatment at discharge was (HR 2.61, 95% CI 1.29-5.29; p=0.008). Afterwards, we undertook multivariate analysis separately in the group treated with insulin (253 patients) and in the group treated with oral drugs or diet only (259 patients). This analysis showed that in the group treated with insulin the glucose level at discharge was not an independent prognostic factor of one-year mortality (HR 1.07, 95% CI 0.95-1.22; p=0.27), whereas in patients treated with hypoglycaemic agents or diet it was significantly associated with a one-year mortality (HR 1.30, 95% CI 1.01-1.68; p=0.049).
Conclusions: 1. Patients with STEMI and DM treated with insulin at hospital discharge have higher risk of death, probably because of more advanced DM and more severe complications, than patients treated with oral drugs or diet. 2. Elevated glucose level at hospital discharge predict one-year mortality only in patients with MI and DM treated with oral drugs or diet.