Sites of interleukin-6 release in patients with acute coronary syndromes and in patients with congestive heart failure.

This study examines the source of elevated interleukin-6 (IL-6) levels in patients with acute coronary syndrome (ACS) and congestive heart failure (CHF). IL-6 is elevated in the peripheral blood of patients with ACS and CHF, but it is not known if this proinflammatory cytokine is from a cardiac or extracardiac source. Blood samples were obtained from the femoral artery, femoral vein, left main coronary artery, and coronary sinus in 57 patients during cardiac catheterization. IL-6 levels from 12 patients with ACS and 12 patients with CHF were compared with the IL-6 levels in 33 patients who had neither of these clinical conditions. Median IL-6 levels in the peripheral and coronary circulation were a minimum fivefold higher in patients with ACS or CHF relative to control patients. An elevated transcardiac IL-6 gradient (coronary sinus-left main level) was present in patients with ACS (median 5.2; 25th and 75th percentiles 3.9 and 29.3 pg/ml, respectively) compared with control patients (median 0, -0.7 and 0.5 pg/ml; p < 0.001), but not in patients with CHF (median 0.4, -0.7 and 3.5 pg/ml; p = NS). Elevated IL-6 levels in patients with ACS derive from a cardiac source, presumably from "inflamed" coronary plaques and areas of myocardial necrosis, whereas elevated levels in patients with CHF are most likely the result of extracardiac production.