Do nondiabetic patients with acute coronary syndromes and hyperglycemia benefit from insulin therapy?

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Abstract

BACKGROUND

Hyperglycemia is a risk factor for adverse outcomes in patients with acute coronary syndromes (ACS), and insulin therapy is recommended for those with an established diagnosis of diabetes. Whether nondiabetic patients with ACS who present with an elevated blood glucose level benefit from insulin administration is less certain.

OBJECTIVE

To investigate the outcomes associated with insulin treatment in nondiabetic patients presenting with ACS and an elevated blood glucose level.

DESIGN

This was a retrospective study of observational data from the National Audit of Myocardial Infarction Project (MINAP). The analysis included patients admitted to hospital between January 2003 and March 2006 with a diagnosis of troponin-positive ACS and a blood glucose level of 11.0 mmol/l or higher. Both patients with ST-segment elevation myocardial infarction (STEMI) and those with non-STEMI were eligible for inclusion.

OUTCOME MEASURES

The primary end points were mortality at 7 and 30 days after hospital admission

RESULTS

Data on hyperglycemia treatment in patients with ACS were recorded by 201 hospitals in England and Wales. During the study period, 190,033 cases of ACS were recorded. The study cohort comprised the 3,835 patients with ACS who had a blood sugar level of 11.0 mmol/l or higher at hospital admission but had not previously been diagnosed with diabetes. Among these patients, 872 (22.7%) received insulin treatment, 135 (3.5%) received an alternative treatment (e.g. dietary modification), and 1,770 (46.2%) did not receive any treatment for hyperglycemia. In the remaining 1,058 cases (27.6%), no hyperglycemic treatment strategy was recorded. The most commonly prescribed insulin-based therapy was the DIGAMI (Diabetes and Insulin-Glucose Infusion in Acute Myocardial Infarction) regimen. Insulin pumps and single-dose insulin strategies were also used. Compared with patients who did not receive treatment, or for whom no treatment was recorded, patients who received insulin were younger (mean age 72 years), had a higher mean blood glucose level (14.8 mmol/l), and were more likely to have STEMI (58.4%). Mortality at 7 and 30 days was lower among insulin-treated patients than those who did not receive treatment (11.6% vs 16.5% and 15.8% vs 22.1%, respectively). Regression analysis controlled for age, sex, blood glucose level, and comorbidities revealed that the relative risk (RR) of death was significantly increased in untreated patients compared with insulin-treated patients at both 7 days (RR 1.56, 95% CI 1.22-2.00, P<0.001) and 30 days (RR 1.51, 95% CI 1.22-1.86, P <0.001). The difference in mortality between treated and untreated patients was most evident among those with ST-segment elevation. The significant reduction in mortality associated with insulin therapy persisted when the analyses were controlled for death occurring on the date of hospital admission.

CONCLUSION

Insulin treatment was associated with a significant reduction in 7-day and 30-day mortality among nondiabetic patients presenting with ACS and a blood glucose level of 11.0 mmol/l or higher.

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