Interleukin-6 and neutrophils are associated with long-term survival after acute myocardial infarction

Abstract 

Background

Assessing acute myocardial infarction (MI) with respect to long-term survival is not easy. Authorities in the field suggest that inflammation predicts short-range (up to 17 months) coronary death. It is not known whether long-term survival is associated with the inflammatory response. In this study, we evaluate the relationships between survival for more than 8 years and inflammation, i.e., circulating interleukin-6 (IL-6) and neutrophil counts, in acute MI.

Methods

Patients with ST-segment elevation MIs (STEMI; n=33) and non-ST-segment MIs (non-STEMI; n=39) in 1996 were included in the study. All STEMI patients received thrombolytic therapy. Acute coronary angiography was not an option. Determination of IL-6 and neutrophils was carried out within 24 h after commencement of pain. The subjects were followed for more than 8 years (until December 31, 2005) using the national death registry. Inflammatory markers at the time of MI were compared with long-term survival (n=35).

Results

At the time of acute MI, survivors for more than 8 years proved to have lower IL-6 (p<0.01) and decreased neutrophil counts (p<0.05). The differences remained (p<0.01 for both markers) when excluding deaths (n=11) occurring in 1996 and 1997. Subsequently, the subjects were divided into two equally sized groups, depending on their IL-6 values at the beginning of the study. As expected, a lower IL-6 was associated with a more favorable long-term prognosis (p<0.01).

Conclusions

Circulating IL-6 predicts long-term survival after acute MI. Neutrophils appear to have prognostic value as well.

Keywords: Interleukin-6, Myocardial infarction, Neutrophil granulocytes, Survival