A targeted treatment for a common heart-failure burden
People with heart failure with preserved ejection fraction, or HFpEF, often live with a difficult mismatch: the heart’s pumping fraction may be preserved, but everyday physical activity can still become exhausting. A new randomized trial from investigators at Mass General Brigham reports that correcting iron deficiency with one intravenous infusion improved exercise-capacity measures in this group over 12 weeks.
The findings come from the IRON-MET HFpEF trial, presented at the 2026 American Heart Association Scientific Sessions and published simultaneously in Circulation. The study examined ferric derisomaltose, an intravenous iron formulation, in participants with symptomatic HFpEF and iron deficiency.
The result is notable because exercise intolerance is one of the central practical problems of HFpEF. It can limit walking, climbing stairs and other ordinary tasks, while treatment options that directly improve physical capacity remain a major focus of research. The study suggests that iron status may be an actionable part of that problem for some patients.
What the trial tested
IRON-MET HFpEF enrolled 65 people with symptomatic HFpEF and iron deficiency. Their median age was 68, and 72% were women. According to the researchers, iron deficiency affects more than half of people with HFpEF.
Forty-four participants were randomly assigned to receive a single 1,000-milligram intravenous dose of ferric derisomaltose. The remaining 21 received placebo. All participants completed cardiopulmonary exercise testing before treatment and again 12 weeks later.
Intravenous delivery was a deliberate part of the study design. The researchers noted that oral iron has not been beneficial in studies involving other forms of heart failure, a result thought to be related to poor gastrointestinal absorption. The trial therefore tested whether a one-time infusion could more reliably restore available iron and translate that change into better exercise performance.
Improvement across several measures
At 12 weeks, peak oxygen uptake, known as VO₂, improved by about 10% in the iron-infusion group and was unchanged in the placebo group. Peak VO₂ is a key marker of cardiorespiratory fitness and an important way to assess how the body performs under exertion.
The researchers also reported improvements in iron availability in the blood. Prespecified secondary measures of exercise capacity moved in the same direction: participants receiving intravenous iron did better in six-minute walk distance, VO₂ at the anaerobic threshold and New York Heart Association functional class than those receiving placebo.
That pattern matters because it reaches beyond a single laboratory measurement. Cardiopulmonary testing captures a physiological response to exertion, while the six-minute walk test and functional class connect more closely to physical ability and symptom burden in daily life. Together, the results point to a possible link between replenishing iron and broader improvements in how participants could tolerate activity.
Lead author Gregory D. Lewis, director of heart failure at the Mass General Brigham Heart and Vascular Institute and a professor of medicine at Harvard Medical School, described the work as the first study to comprehensively evaluate exercise-response patterns after iron repletion in people with HFpEF and iron deficiency.
Why iron could matter
Iron is relevant to more than the production of red blood cells. It is also involved in the biological processes that support energy production and oxygen use. In a population already limited by shortness of breath and reduced exertional capacity, low available iron could add another obstacle to physical performance.
The trial does not establish that iron deficiency is the sole driver of exercise limitation in HFpEF, nor does it turn a single infusion into a universal treatment. HFpEF is a complex condition, and the study was designed around a specific subgroup: people with symptoms and documented iron deficiency. Still, its findings provide a clear reason to investigate that subgroup more closely.
They also raise a practical clinical question for future research: whether recognizing and treating iron deficiency could complement other efforts to manage the physical limitations of HFpEF. The study’s design is especially useful in this regard because it compared treatment with placebo and measured changes over a defined 12-week interval.
An encouraging signal, not a final answer
The study is relatively small, with 65 participants, and the source text notes that the authors identify limitations. Its results therefore need confirmation in larger trials before they can settle questions about longer-term outcomes, broad treatment use or how the approach should fit into routine care.
But the signal is clinically meaningful: a single IV dose was associated with improved peak oxygen uptake and several secondary exercise measures while the placebo group showed no change in the primary fitness measure. For people whose condition can make modest activity feel out of reach, an intervention that improves measurable capacity deserves close attention.
For now, the work reframes iron deficiency in HFpEF as more than a laboratory finding. It may be a modifiable contributor to the limits patients experience, and a subject for the larger studies needed to determine who benefits most and how durable those benefits may be.
This article is based on reporting by Medical Xpress. Read the original article.
Originally published on medicalxpress.com
