NEW ORLEANS — A device that allows therapy adjustments in the setting of heart failure with preserved ejection fraction (HFpEF) by detecting lung fluid in advance of decompensation reduced major events, according to a new randomized trial.

In the trial, called IMPEDANCE-HF, the odds ratio (OR) of all-cause mortality among those managed with the device compared with those who were not was reduced by 65% at 7 years (OR, 0.35; P < .01), reported Michael Kleiner Shochat, MD, PhD, senior physician in the Interventional Cardiology Unit at the Hillel Yaffe Medical Center in Hadera, Israel.

“The secret of success is to enable us to intervene at the preclinical stage when the reaction to treatment is more powerful,” Shochat said.

Reduction in Hospitalizations

There was an 81% (OR, 0.19; P < .01) reduction in HF hospitalizations and in HF-related mortality (OR, 0.19; P < .01) for those managed with the impedance device compared with those who were not at the end of the 7-year follow-up.

“Direct monitoring of pulmonary congestion may redefine heart failure management,” Shochat told Medscape Medical News at the American College of Cardiology (ACC) Scientific Session 2026, where the data were scheduled for presentation as a late breaker.

Although the study was not presented as planned due to an acute illness, the data were released at a news conference. An ACC spokesperson announced that the findings are considered part of the meeting’s program.

The noninvasive impedance device used in this study (Edema Guard Monitor, CardioSet Medical) was approved for HF with reduced ejection fraction (HFrEF) in 2025. The underlying concept is not new, according to a review paper of this technology, but this specific study device was designed to eliminate chest wall noise, a previous hurdle to a viable fluid detection, Shochat said.

To isolate the lung from chest wall impedance, which produces a much stronger signal, an algorithm was developed by assessing multiple variables with machine learning in healthy individuals. Testing was done separately for men and women. The algorithm allows normal lung impedance to be calculated at the individual level. Changes from these normal levels allow lung fluid levels to be assessed.

For clinical application, three zones relative to the patient’s predicted normal lung impedance were established based on signals of pulmonary edema. These were green, meaning no need for change in therapy; yellow, meaning diuretic uptitration is recommended; and red, meaning uptitration is mandatory.

These zones corresponded to interstitial edema, a transition status from interstitial to alveolar edema, and alveolar edema, respectively. For clinical guidance, even mild alveolar edema is interpreted as sufficient for a mandatory increase in diuretic dose.

Diuretics Downregulated

Guidance for dose downregulation can be derived from the same color-coded zones as impedance moves from a classification of red to yellow and from yellow to green.

In the single-blind IMPEDANCE-HF trial, 150 patients with HFpEF were randomly assigned to care guided by the lung impedance device or usual care. Eligibility criteria included an HF-related hospitalization in the prior year, a left ventricular ejection fraction greater than 50%, and an N-terminal pro-B-type natriuretic peptide (NT-proBNP) level ≥ 300 pg/mL. There were no exclusions based on HF functional class.

Based on the study, diuretic management of HFpEF was initiated more quickly and adjusted more frequently when the impedance device was used. Shochat said the improvements in clinical outcome in the experimental arm of the study are best explained by timing and not intensity.

In up to 35% of the cases, patients in the impedance device arm were treated with diuretics earlier than those managed with usual care. Both diuretic upregulations (1873 vs 1049) and downregulations (811 vs 161) occurred more frequently with impedance monitoring, Shochat reported.

Based on congestion leading to hospitalization, impedance-guided care “kept patients in the therapeutic range nearly twice as long,” Shochat said. He also reported that cases of over-diuresis were reduced.

The Edema Guard Monitor was cleared by the FDA in September 2025 for HFrEF and is now available in the United States, said Shochat, who first published HFrEF clinical data 10 years ago. Long-term benefits from a randomized trial of patients with HFrEF were published in 2021.

The ACC-invited discussant for this paper, Leslie L. Davis, PhD, ANP-BC, an associate professor in the School of Nursing at the University of North Carolina at Chapel Hill, said the IMPEDANCE-HF trial is important. Although she was not able to deliver her planned remarks about the study during the late breaker session, she did speak with Medscape Medical News after the ACC meeting.

Highly Representative HFpEF Population Studied

Davis emphasized that the outcomes were demonstrated “exactly in the population we see in the clinic.”

This was reflected by baseline characteristics that included a majority female population (~61%), an elevated average BMI (~34), and an elevated stress hormone (median NT-proBNP of ~1200 pg/mL). About 40% had chronic atrial fibrillation or flutter, and the average New York Heart Association class was 2.9.

“These are challenging patients,” she said, noting, for example, that patients with obesity are often harder to evaluate for the risk for decompensation.

Davis did have some questions she intended to pose about the application in the real-world that went unanswered, such as: Would the device most commonly be used in a clinic or at home? And what would be a recommended frequency of monitoring?

Davis noted that it is well within the scope of practice for members of an HF team, including advanced practice providers such as nurse practitioners, to diagnose and manage early decompensation detected by this noninvasive device, optimally preventing hospitalization.

Overall, she was impressed with the underlying concept and that this device outperforms other noninvasive options for detecting decompensation before signs and symptoms appear, signaling modification of treatment through the three zones described by Shochat.

“This could offer us an opportunity to get ahead of decompensation,” she said, speaking about “a sweet spot in timing” of HFpEF, which is associated with substantial morbidity and mortality.

Despite the growing attention directed toward management of HFpEF, “this remains a vulnerable population for which we need more tools,” she said.

Shochat reported being a principal stockholder in CardioSet Medical, which developed the impedance device tested in this study. Davis reported having no potential conflicts of interest.