Clinical research: risk predictors and coronary disease
Diabetes mellitus: the major risk factor in unstable coronary artery disease even after consideration of the extent of coronary artery disease and benefits of revascularization

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Abstract

Objectives

This study was designed to study the influence of diabetes on the outcome of unstable coronary artery disease (CAD).

Background

Diabetes mellitus is a major contributor to CAD. Despite improvement in the management of patients with unstable coronary syndromes, this condition is still linked to a substantially increased mortality and morbidity among diabetic patients. Recent evidence advocates early revascularization in unstable coronary syndromes. Diabetic patients subjected to coronary interventions under stable conditions have a higher risk for complications and a more dismal prognosis than nondiabetic subjects. Accordingly, it is of considerable interest to obtain further information regarding the best possible management of diabetic patients with unstable CAD.

Methods

A total of 2,158 patients without and 299 with diabetes mellitus were randomized to an early invasive or a noninvasive strategy. The severity of CAD was expressed as the number and extent of vessel involvement.

Results

Three-vessel disease was diagnosed in 42% of diabetic and 31% of nondiabetic patients (p = 0.006). The percentages of patients with ST-depression and troponin-T >0.03 μg/l at admission were comparable among diabetic and nondiabetic patients. Mortality and reinfarction after 12 months were more frequent among diabetic than nondiabetic patients in both treatment groups. Diabetes remained a strong independent predictor for death and myocardial infarction in multivariable analysis. The invasive strategy reduced event rate in nondiabetic patients from 12.0% to 8.9% (odds ratio [OR] = 0.72; confidence interval [CI] 0.54 to 0.95; p = 0.019) and in diabetic patients from 29.9% to 20.6% (OR 0.61; CI 0.36 to 1.04; p = 0.066). In a multivariate analysis including the extent of CAD, diabetes remained a strong independent predictor of the combined end point (relative risk [RR] 2.40; CI 1.47 to 3.91; p = 0.0001) and of mortality (RR 5.43; CI 2.09 to 14.12; p = 0.001).

Conclusions

An invasive strategy improved outcome for both diabetic and nondiabetic patients with unstable CAD. However, diabetes mellitus remained an independent and important risk factor for death and myocardial infarction in the invasive group. Thus, factors beyond the extent of flow-limiting coronary lesions are of considerable importance for outcome in diabetic subjects with unstable coronary syndromes.

Abbreviations

CABG
coronary artery bypass graft
CAD
coronary artery disease
CK
creatine kinase
DM
diabetes mellitus
ECG
electrocardiogram
MI
myocardial infarction
PCI
percutaneous coronary intervention
RIKS-HIA
Register of Information and Knowledge about Swedish Heart Intensive
RR
risk ratio

Cited by (0)

The FRISC II trial was supported by and organized in collaboration with the Pharmacia and Upjohn Company. The Swedish Heart-Lung Foundation supported this part of the study.