Interleukin-6 and Outcomes in Acute Heart Failure: An ASCEND-HF Substudy

Background: The inflammatory cytokine IL-6 has been previously implicated in the pathophysiology of acute decompensated heart failure (HF). Prior observations in acute HF patients have suggested that IL-6 may be associated with outcomes and modulated by nesiritide. We aimed to evaluate the associations between serial IL-6 measurements, mortality and rehospitalization in acute HF. Methods and Results: We analyzed the associations between IL-6 in acute HF, readmission, and mortality (30 and 180 days) using a cohort of 883 hospitalized patients from the ASCEND-HF trial (nesiritide vs placebo). Plasma IL-6 was measured at randomization (baseline), 48-72 hours, and 30 days. The median IL-6 was highest at baseline (14.1 pg/mL) and decreased at subsequent time points (7.6 pg/mL at 30 days). In a univariable Cox regression analysis, the baseline IL-6 was associated with 30- and 180-day mortality (hazard ratio per log 1.74, 95% confidence interval 1.09-2.78, P =.021; hazard ratio 3.23, confidence interval 1.18-8.86, P =.022, respectively). However, there was no association after multivariable adjustment. IL-6 at 48-72 hours was found to be independently associated with 30-day mortality (hazard ratio 8.2, confidence interval 1.2-57.5, P=.03), but not 180-day mortality in multivariable analysis that included the ASCEND-HF risk model and amino terminal pro-B-type natriuretic peptide as covariates. In comparison with placebo, nesiritide therapy was not associated with differences in serial IL-6 levels. Conclusions: Although elevated IL-6 levels were associated with higher all-cause mortality in acute HF, no independent association with this outcome was identified at baseline or 30-day measurements. In contrast with prior reports, we did not observe any impact of nesiritide over placebo on serial IL-6 levels.