Should oral glucose tolerance test be a routine examination after a myocardial infarction?

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Abstract

Background: Diabetes mellitus (DM) and impaired glucose tolerance (IGT) are important cardiovascular risk factors. The objective of this study was to assess the prevalence of DM and IGT in patients discharged from the CCU without known DM after a myocardial infarction. Methods: One hundred and ten patients, men and women aged 31–80 years with a myocardial infarction 1–12 months before inclusion were examined with oral glucose tolerance test. Patients with known DM were excluded. A standard oral glucose test (OGTT) with 75 g of glucose was performed. Results: IGT was observed in 29 (26%) patients and DM in 13 (12%) patients in the OGTT. If only fasting plasma glucose (FPG) was used alone five (38.5%) patients with diabetes subjects and three (10.3%) with IGT were identified. Thus, a FPG test alone identified only 19.0% of the patients with pathological OGTT. The prevalence of DM and IGT in patients discharged from the CCU after a myocardial infarction without known DM diagnosis was high (38%). A fasting glucose alone failed to identify more than 80% of the patients with pathological glucose tolerance in this study. Conclusion: Since pathological glucose tolerance is an important cardiovascular risk factor, oral glucose tolerance test should be considered as a routine test after a myocardial infarction in subjects without known DM.

Introduction

Diabetes mellitus (DM) is a well-known risk factor for cardiovascular mortality [1], [2]. There are also studies indicating that people with prediabetic conditions, such as impaired glucose tolerance (IGT), have an increased risk for cardiovascular disease [3], [4]. The growing knowledge about the close relationship between DM and cardiovascular morbidity and intervention studies showing that the poor prognosis in both type I and type II DM can be improved [5], [6], [7], has put focus on the relevance of identification of patients with IGT and DM. This is especially important in patients who have suffered from a myocardial infarction, since the combination of coronary disease and DM is deleterious [8].

Recently, a high prevalence of undiagnosed diabetes and IGT was reported in a study of 181 consecutive patients admitted to a coronary care unit with acute myocardial infarction [9]. In that study standardised oral glucose tolerance tests were performed at discharge and again 3 months later.

The aim of this study was to assess the prevalence of DM and IGT in patients discharged from the CCU without known diagnosis DM after a myocardial infarction.

Section snippets

Subjects

One hundred and ten patients, men and women aged between 31 and 80 years with a previous acute myocardial infarction were included. The inclusion criterion was hospital-diagnosed myocardial infarction occurring 1–12 months before the examination. A majority of the patients were recruited at the step-down unit 2–3 days after the myocardial infarction. The examinations of this study were performed 1–12 months after the index event. The exclusion criterion was known DM. The patients were recruited

Results

Baseline characteristics of all individuals enrolled are shown in Table 1. Almost 75% of study group were male and 25% were female. Forty-nine percent of patient had undergone PTCA and 20% CABG.

Table 2 shows the prevalence of glucose abnormalities among the examined patients. The 2-h PG was elevated in 42 (38%) of the 110 patients. IGT was observed in 29 (26%) patients and DM in 13 (12%) patients. FPG was ≥7.0 mmol/l in five subjects and between 6.1 and 6.9 mmol/l in nine subjects.

FPG was ≥7.0

Discussion

In this study the prevalence of DM and IGT in patients discharged from the CCU without the known DM after a myocardial infarction was 38%. Twelve percent had DM and 26% IGT.

This observation was based on the result of an oral glucose tolerance test. We also examined whether a fasting glucose could identify these patients, making the OGTT unnecessary. The revised recommendation from WHO and American Diabetes Association (ADA) [12] have emphasised the use of the fasting glucose diagnostic criteria

Acknowledgements

The study has been supported by grants from Karolinska Institute and the Swedish Medical Society.

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    However, in the Euro Heart Survey adverse outcomes at 1 year were related to newly diagnosed diabetes, but not to IFG or IGT [20]. Prior cross-sectional studies have been somewhat limited: (a) only one study from China [21] has assessed AGT prevalence in NSTEMI; (b) only two studies in unselected myocardial infarction patients have assessed temporal changes in AGT by serial OGTT [5,8,22]; (c) several studies have methodological issues including retrospective design [11,23], inclusion of patients with known diabetes [14], incomplete OGTT testing [6,8,9,11,23], differences in the classification of ACS [9,10,13,21], or diabetes [23], differences in the timing of OGTT in relation to the ACS event [11–14,21,23], and high rates of revascularization [14]. The aims of this study were to describe the prevalence and temporal change in glucose tolerance in NSTEMI patients without known DM.

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