Does high-normal 2-hour post load plasma glucose after myocardial infarction in patients with normal glucose tolerance adversely affect prognosis?

Abstract

Abstract Background Type 2 diabetes mellitus (DM) and pre-DM, newly diagnosed after MI in patients without known DM adversely affects prognosis. 2-hour post-load glucose (2h-PG) predicts post-MI prognosis better than fasting plasma glucose (FPG). Plasma glucose below the conventional threshold for the diagnosis of impaired fasting glucose (IFG) and impaired glucose tolerance (IGT), affects post-MI prognosis. Purpose To test whether high-normal post-load plasma glucose in patients with normal glucose tolerance (NGT) would affect post-MI prognosis and whether FPG or 2h-PG increases this risk. Methods Retrospective cohort analysis of 425 MI survivors without known DM and with NGT followed up for (death and non-fatal MI) as MACE. MACE in patients with 2h-PG > median for the whole cohort (Group 2), was compared with those at or below (Group 1). Event free survival in the two groups was estimated from the Kaplan–Meier curves and compared using log-rank test. Cox proportional hazard regression identified predictors of MACE. Continuous net reclassification improvement (NRI>0) and integrated discrimination improvement (IDI) and c-statistics determined the added predictive value of glycaemic matrices. Results Median 2h-PG was 6.3 mmol/l. 219 patients in Group 1 and 206 in Group 2. Group 2 had higher age, prevalence of hypertension, hypercholesterolaemia, ST-segment depression and higher heart rate and GRACE scores. Median follow-up was 40.6 months. MACE was more frequent in Group 2 than Group 1 (OR 2.82, 95% CI 1.55 to 5.16, p<0.001). MACE-free survival was higher in Group 1 (HR 2.43, 95% CI 1.53 to 3.85, p<0.001). Group 2 (HR 2.42, 95% CI 1.44 to 4.04, p<0.001) predicted the MACE-free survival. 2h-PG, but not the FPG independently predicted of MACE (HR 1.73, 95% CI 1.31 to 2.30, p<0.001). Addition of 2h-PG to models containing FPG and other variables improved their predictive performance (NRI>0 0.5062, p<0.001; IDI 0.0376, p=0.003). The c-statistic increased when 2h-PG was added to the GRACE score only model (δAUC 0.037, 95% CI 0.012 to 0.081, p=0.046). Conclusion(s) This study suggests that “high-normal” 2h-PG is an independent predictor of post-MI prognosis. Normoglycaemic patients with 2h-PG ≥6.4 mmol/l, had worse post-MI prognosis compared to those with 2h-PG ≤6.3 mmol/l. The risk of MACE increased with increasing 2h-PG within the normal range. FPG had no effect on prognosis. Funding Acknowledgement Type of funding source: None