Introduction Patients with dysglycaemia at the time of ST-elevation myocardial infarction (STEMI) have a worse prognosis. The reasons for this are not entirely clear. Admission hyperglycaemia has been associated with larger infarct size.
The aims of this study were to examine the relation of acute and chronic glycaemic state to myocardial scar and salvage characteristics in patients with reperfused ST-elevation myocardial infarction.
Methods Fifty-six patients treated for first ST-elevation myocardial infarction (STEMI) without a pre-existing diagnosis of Diabetes mellitus were prospectively enrolled between January and December 2010. Glycosylated haemoglobin (HbA1c) and glucose levels were sampled on admission to the emergency cardiac ward. Patients underwent cardiac magnetic resonance (CMR) examination during the index admission (median day 2 for CMR, IQR 2 days), with assessment of area-at-risk (STIRs), Infarct size (IS%), late microvascular obstruction (MVO%), and left ventricular function. Population characteristics are presented in table 1. There were no significant differences between patients receiving Primary Percutaneous Coronary Intervention (PPCI) or thrombolysis, so these were grouped for analysis.
Patients were dichotomised into groups above and below the median both for admission glucose level and separately for HbA1c level before comparison between groups using Independent samples t test. Spearman's rank correlation was used to compare non-parametric data. Correlations with a p<0.1 were entered into a multivariate linear regression model.
Results When patients were dichotomised into glucose levels below (<7.8 mmol/l) and above the median (¡Ý7.8 mmol/l), the supra-median group were significantly older (64.7 years vs 57.1 years, p=0.018) and had greater Infarct size (28.33% vs 18.46%, p=0.007).
Dichotomising patients by HbA1c into levels below the median (<5.9%) and above the median (¡Ý5.9%), the supra-median group had significantly greater glucose levels (8.8 mmol/l vs 7.1 mmol/l, p=0.011), less ST-segment resolution (51.6% vs 75.5%, p=0.007), greater MVO% (2.77% vs 1.11%, p=0.049), greater intra-myocardial haemorrhage (IMH%) (1.96% vs 0.61%, p=−0.015), and lower myocardial salvage index (MSI%) (43.30% vs 65.15%, p=0.003).
Correlations between infarct characteristics and admission glucose and HbA1c are shown in table 2. Admission glucose correlated significantly with age and IS%, while HbA1c correlated significantly with time to reperfusion and MSI%.
On multivariate linear regression analysis however, glucose was not a predictor of IS% (R=0.549, R2=0.302, Age t=3.441, p=0.001, time to reperfusion t=2.708, p=0.009, glucose- not significant), and HbA1c was not a predictor of MSI% (R=0.453, R2=0.206, age t=−2.529, p=0.015, time to reperfusion t=−2.237, p=0.030, HbA1c-not significant).
Conclusions/implications Admission Glucose levels are associated with larger infarct size, and HbA1c levels are associated with reduced myocardial salvage. However, glycaemic status is not an independent predictor of infarct size or salvage when time to reperfusion is taken in to consideration.