More Heart Failure Patients Could Benefit From Lung Impedance Monitoring

NEW ORLEANS — For people with heart failure with preserved ejection fraction (HFpEF), monitoring for early fluid accumulation in the lungs allowed for earlier intervention and thus fewer heart failure (HF) hospitalizations, a small randomized trial found.

With HF management guided by noninvasive measurement of pulmonary congestion via lung impedance as opposed to usual care, patients had HF hospitalizations reduced by an impressive 72% at 1 year (HR 0.28, P<0.01), reaching an 81% reduction at 7 years (HR 0.19, P<0.01), according to Michael Kleiner Shochat, MD, PhD, of Hillel Yaffe Medical Center in Hadera, Israel.

There was no significant benefit in all-cause mortality at 1 year (HR 0.14, P=0.06), but one did emerge at 7 years (HR 0.35, P<0.01). Similarly, a drop in HF-related mortality was not evident at 1 year (HR 0.24, P=0.2) but was there at 7 years (HR 0.19, P<0.01) in the 150-person study, Shochat reported here at the American College of Cardiology (ACC) annual meeting.

The evidence for lung impedance monitoring to improve HF outcomes thus expands beyond what was established 10 years ago in the setting of HF with reduced ejection fraction. The device in question, the Edema Guard Monitor from CardioSet, is already FDA 510(k) cleared for impedance monitoring.

Benefits of going the lung impedance route in HFpEF are believed to be related to triggering earlier diuretic intervention, not treatment intensity, as pulmonary congestion is known to precede HF symptoms by days or weeks, Shochat explained.

He noted that unlike available noninvasive tools to measure congestion, which are indirect and insensitive, the CardioSet device in the study directly captures lung fluid changes by taking away chest wall noise on traditional impedance assessment. Such lung impedance monitoring is noninvasive, simple, and scalable, he added.

Of note, besides its small sample, a major limitation of the present study was its single-blind design.

“I really like this. I think that it really helps us understand the physiology of congestion a lot better,” said Melvin Echols, MD, of Morehouse School of Medicine in Atlanta, nonetheless. “Clearly this is showing us that the impedance values, particularly once you remove the chest noise, actually are very valuable and very helpful in determining what is actually a diuresis state. So I think overall, this actually offers some very potential, sort of nuanced therapies.”

“I think more data needs to come in a randomized, controlled trial fashion, obviously, but I still think that it is showing us that there may be benefits to using [lung impedance],” Echols said at a press conference.

Shochat’s group had conducted a single-center trial in which 150 HFpEF patients were randomized to lung impedance-guided therapy or usual care. They’d sought patients who’d had a HF hospitalization/emergency department visit within the prior year and a left ventricular ejection fraction (LVEF) >50%.

The two study arms were well matched at baseline. Mean age was around 76 years, about 62% of the cohort were women, and body mass index averaged 34 kg/m². The mean LVEF was 60%, and median N-terminal pro-brain natriuretic peptide was between 1,200-1,250 pg/mL.

The lung impedance ratio — a fluid index describing what lung impedance is versus what it should be, and therefore creating a scale of when a diuretic is needed — was -22% from normal at baseline.

People were kept in the therapeutic range for longer (time in therapeutic range median 96.6% vs 50.0%, P<0.01) with lung impedance monitoring, Shochat reported.

In the lung impedance-guided group, diuretic therapy was up-titrated in 1,873 instances versus 1,049 in the control group. The level of lung congestion prompting these up-titrations was -20.8% versus -35.4% — hence the conclusion that the monitoring triggered earlier intervention.

Meanwhile, the number of down-titrations reached 811 versus 161.