Iron deficiency is common in HFpEF, but evidence supporting iron repletion in this population remains limited. The IRONMET-HFpEF trial, published in Circulation, evaluated whether intravenous ferric derisomaltose (FDI) could improve exercise capacity compared with placebo. This double-blind, placebo-controlled trial randomized 65 patients with HFpEF and iron deficiency to receive a single 1,000-mg intravenous dose of FDI (n=44) or placebo (n=21).

The primary endpoint was change in peak oxygen uptake (peak VO₂) at 12 weeks.Peak VO₂ increased by 1.2 mL/kg/min in the FDI group, compared with 0.1 mL/kg/min with placebo. The between-group difference was 1.1 mL/kg/min (95% CI, 0.2–1.9; P=0.02).FDI also improved 6-minute walk distance by an additional 41.1 metres and oxygen uptake at the anaerobic threshold. Improvement in New York Heart Association functional class was more frequent with FDI…