Interleukin-6 in Patients With Heart Failure and Preserved Ejection Fraction

Interleukin (IL)-6 is a central inflammatory mediator and potential therapeutic target in heart failure (HF). Prior studies have shown that IL-6 concentrations are elevated in patients with HF, but much fewer data are available in heart failure with preserved ejection fraction (HFpEF). This study aims to determine how IL-6 relates to changes in cardiac function, congestion, body composition, and exercise tolerance in HFpEF. Clinical, laboratory, body composition, exercise capacity, physiologic and health status data across 4 National Heart, Lung, and Blood Institute-sponsored trials were analyzed according to the tertiles of IL-6. IL-6 was measured in 374 patients with HFpEF. Patients with highest IL-6 levels had greater body mass index; higher N-terminal pro-B-type natriuretic peptide, C-reactive protein, and tumor necrosis factor-α levels; worse renal function; and lower hemoglobin levels, and were more likely to have diabetes. Although cardiac structure and function measured at rest were similar, patients with HFpEF and highest IL-6 concentrations had more severely impaired peak oxygen consumption (12.3 ± 3.3 mL/kg/min 13.1 ± 3.1 mL/kg/min 14.4 ± 3.9 mL/kg/min, P < 0.0001) as well as 6-minute walk distance (276 ± 107 m vs 332 ± 106 m vs 352 ± 116 m, P < 0.0001), even after accounting for increases in IL-6 related to excess body mass. IL-6 concentrations were associated with increases in total body fat and trunk fat, more severe symptoms during submaximal exercise, and poorer patient-reported health status. IL-6 levels are commonly elevated in HFpEF, and are associated with greater symptom severity, poorer exercise capacity, and more upper body fat accumulation. These findings support testing the hypothesis that therapies that inhibit IL-6 in patients with HFpEF may improve clinical status. (Clinical Trial Registrations: Phosphodiesterase-5 Inhibition to Improve Clinical Status and Exercise Capacity in Diastolic Heart Failure [RELAX], NCT00763867; Nitrate's Effect on Activity Tolerance in Heart Failure With Preserved Ejection Fraction, NCT02053493; Inorganic Nitrite Delivery to Improve Exercise Capacity in HFpEF, NCT02742129; Inorganic Nitrite to Enhance Benefits From Exercise Training in Heart Failure With Preserved Ejection Fraction [HFpEF], NCT02713126).