Wearable Fluid Sensor Lowers Risk for HF Rehospitalizations

NEW ORLEANS — A wearable device that monitors thoracic fluid and can signal elevated levels can improve outcomes after heart failure hospitalization, according to a comparative but nonrandomized trial.

In this study, management adjustments made in response to a threshold alert from the device led to several improvements in outcome at 90 days, including a significant 38% reduction in the primary outcome of rehospitalization, relative to controls (= .02), reported John P. Boehmer, MD, at the joint scientific sessions of the American College of Cardiology and the World Heart Federation.

The same relative risk reduction at 90 days was observed for a composite outcome of time to first hospitalization, visit to an emergency room, or death (hazard ratio, 0.62; = .03).

Quality of life, as measured with the Kansas City Cardiomyopathy Questionnaire (KCCQ), improved steadily in both the experimental and control arm over the 90-day study, but the curves separated at about 30 days, Dr. Boehmer reported. By the end of the study, the mean KCCQ difference was 12 points favoring the experimental arm on a scale in which 5 points is considered clinically meaningful.

70% report improved quality of life

“Responder analysis revealed that nearly 70% of patients in the arm managed with the monitor reported a clinically meaningful improvement in quality of life, compared to 50% of patients in the control arm,” said Dr. Boehmer, professor of medicine and surgery at Penn State Health, Hershey.

Fluid overload is an indication of worsening disease and a frequent cause of heart failure hospitalization. The Zoll Heart Failure Monitoring System (HFMS) that was tested in this study already has regulatory approval. It is equipped to monitor several biomarkers, including heart rate and respiration rate, but its ability to measure lung fluid through low electromagnetic radiofrequency pulses was the function of interest for this study.

In this nonrandomized study, called Benefits of Microcor in Ambulatory

Decompensated Heart Failure (BMAD), a control arm was enrolled first. By monitoring the initial patients enrolled in the control arm, the investigators established a threshold of thoracic fluid that would be used to trigger an alert in the intervention arm. This ultimately was defined as 3 standard deviations from the population mean.

Patients were eligible for this study if they were discharged from a hospital with heart failure in the previous 10 days. Of exclusion criteria, a short life expectancy (< 1 year) and a wearable cardiac defibrillator were notable. Left ventricular ejection fraction (LVEF) was not considered for inclusion or exclusion.

All subjects participated in weekly phone calls and monthly office visits. However, both investigators and patients were blinded to the device data in the control arm. Conversely, subjects and investigators in the intervention arm were able to access data generated by the device through a secure website.

Of the 245 eligible patients in the control arm, 168 were available for evaluation at 90 days. Among the 249 eligible patients in the intervention arm, 176 were included in the 90-day evaluation. Of those who were not available, the most common reason was study withdrawal. About 20% died before the 90-day evaluation.

The majority of patients in both arms were in class III or IV heart failure. About half had LVEF less than 40%, and more than 40% of patients in each group had chronic kidney disease (CKD). Roughly 55% of patients were at least 65 years of age.

At 90 days, the absolute risk reduction in rehospitalization was 7%, producing a number to treat with the device of 14.3 to prevent one rehospitalization. In a subgroup stratification, the benefit was similar by age, sex, presence or absence of CKD, LVEF greater or lower than 40%, Black or non-Black race, and ischemic or nonischemic etiology.

Patient access to data considered a plus

If lack of randomization is a weakness of this study, the decision to unblind the data for both investigators and patients might not be, according to Lynne Stevenson, MD, director of the cardiomyopathy program, Vanderbilt University Medical Center, Nashville, Tenn.

“You might be criticized for this [allowing patients to monitor their data], but I actually think this is a strength of the study,” said Dr. Stevenson, who believes the growing trend to involve heart failure patients in self-management has been a positive direction in clinical care.

She indicated that, despite the potential bias derived from being aware of fluid fluctuations, this information might also be contributing to patient motivation for adherence and appropriate lifestyle modifications.

Biykem Bozkurt, MD, PhD, chair of cardiology at Baylor College of Medicine, Houston, made a similar point but for a different reason. She expressed concern about the work that monitoring the wearable device creates for clinicians. Despite the positive data generated by this study, Dr. Bozkurt said the device as used in the study demanded “a lot of clinical time and effort” when these are both in short supply.

While she called for a larger and randomized study to corroborate the results of this investigation, she also thinks that it would make sense to compare the clinical value of this device against alternative methods for monitoring heart failure, including other wearable devices. Dr. Bozkurt asserted that some of the most helpful devices from a clinical perspective might be those that patients monitor themselves.

“Hopefully in the future, we will be offering tools that provide patients information they can use without the immediate need of a clinician,” she said.

Dr. Boehmer reports financial relationships with Abbott, Boston Scientific, Medtronic, and Zoll Medical Corporation, which provided the funding for this study. Dr. Stevenson reports no potential conflicts of interest. Dr. Bozkurt reports financial relationships with Abbott, Amgen, AstraZeneca, Boehringer Ingelheim, Cardurion, LivaNova, Relypsa, Renovacor, Sanofi-Aventis, and Vifor.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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