Sensible Medical Innovations Lung fLuid Status Monitor Allows rEducing Readmission Rate of Heart Failure Patients (SMILE)—A Randomized Controlled Study

Article Citation:

Peter M. Eckman (2017) Sensible Medical Innovations Lung fLuid Status Monitor Allows rEducing Readmission Rate of Heart Failure Patients (SMILE)—A Randomized Controlled Study. Journal of the Minneapolis Heart Institute Foundation: January 2017, Vol. 1, No. 1, pp. 84-86.

Research Article

Peter M. Eckman, MD

Minneapolis Heart, Minneapolis, MN

Address for correspondence:
Minneapolis Heart Institute
920 E 28th Street #300
Minneapolis, Minnesota 55407
Tel: 612-863-3900

E-mail: Peter.Eckman@allina.com

ABSTRACT

Heart failure is the leading cause of hospitalization, and reducing potentially preventable readmissions has been a major goal for many health care organizations. The potential for penalties from the Centers for Medicare & Medicaid Services for poor performance has heightened concern. An implantable pulmonary artery pressure sensor has been shown to reduce risk of rehospitalization for heart failure, but the invasive nature, expense, and variable payor coverage have blunted adoption. The Sensible Medical Innovations Lung fLuid Status Monitor Allows rEducing Readmission Rate of Heart Failure Patients (SMIILE) study is a prospective, randomized, controlled, multicenter study of patients hospitalized with a diagnosis of acute decompensated heart failure. The intervention of readings from a wearable vest that measures lung fluid using dielectric sensing will be compared with standard of care. The primary efficacy endpoint is the rate of heart failure readmissions during the follow-up period. The study anticipates enrollment of 380 participants.

Keywords: heart failure, readmissions, lung fluid, dielectric, remote monitoring

INTRODUCTION

Heart failure is the leading cause of hospitalization, and reducing potentially preventable readmissions has been a major goal for many health care organizations. The potential for penalties from CMS for poor performance has heightened concern. Although this metric has limitations,1 there is no question that keeping patients well enough to remain at home is an important goal of great interest to patients. Remote monitoring has been proposed as a potential solution, but results from noninvasive telemedical approaches have been disappointing.2–4 A collaborative care patient-centered disease management intervention was also recently studied, but no impact on 1-year hospitalization rate was observed.5 In contrast, an implantable pulmonary artery pressure sensor has been shown to reduce risk of rehospitalization for heart failure,6but the invasive nature, expense, and variable payor coverage have blunted adoption.

BACKGROUND

The electromagnetic properties of biologic tissues vary with fluid content. Low power signals can be applied to one side of the chest, and the signal received on the other side will vary based on the electromagnetic characteristics of the material through which it is transmitted, such as lung tissues. Since water has a very high dielectric coefficient, dielectric coefficients of tissues are determined predominantly by their fluid content. A portable vest that uses remote dielectric sensing (ReDS) to quantify lung fluid content (Figure 1) has been developed by Sensible Medical Innovation. The ReDS system includes two sensors, which are embedded in the vest. One sensor is on the anterior chest and the posterior sensor is on the back. An important difference from bio-impedance devices is that remote dielectric sensing is not dependent on electrode placement, fat content, or skin moisture. Measurements are completed in 90 seconds, and fluid volume is represented as a percentage of fluid volume to total lung volume. Measurements are subsequently transmitted to a secured cloud portal for clinician review (Figure 2) and subsequent medication adjustment, if indicated based on readings.

FIGURE 1
Portable ReDS vest.

FIGURE 2
Serial measurements of lung fluid content via web portal (SensiCloud).

Remote dielectric sensors have been found to be accurate in assessing pulmonary fluid status.7 ReDS measurements demonstrated intraclass correlation between computed tomography (CT) and ReDS of 0.90 (confidence interval [CI] 0.80–0.95), and good temporal resolution (Figures 3, 4). A multicenter, prospective study of stage C heart failure patients was conducted at 3 sites in Israel. Notifications to physicians were generated if the ReDS measurement crossed a prespecified threshold; therapeutic intervention was at the discretion of the physician with a goal of returning the pulmonary fluid content back to the normal range. A total of 50 patients were discharged and completed home follow-up with an average period of 82.9 ± 25.5 days. The average age was 73.8 ± 10.3 years and the average body mass index (BMI) was 28.6 ± 4.7 kg/m2. Most (62%) were male and New York Heart Association class 3 (74%). The readmission rate during the ReDS-guided management period was 4%, which was compared with the pre-ReDS (30%) and post-ReDS (19%) guided periods. The hazard ratio between the pre-ReDS period and the ReDS-management period was 0.07 with a 95% CI of 0.01 to 0.54 and a P value of 0.01.8

FIGURE 3
Correlation between lung fluid content as measured by ReDS or high-resolution chest CT.

FIGURE 4
Measurement of ReDS and CT of lung fluid content over time in a porcine model.

STUDY SUMMARY

The Sensible Medical Innovations Lung fLuid Status Monitor Allows rEducing Readmission Rate of Heart Failure Patients (SMILE) study is a prospective, randomized, controlled, multicenter study of patients hospitalized with a diagnosis of acute decompensated heart failure. The intervention is a wearable vest that provides a noninvasive measurement of lung fluid content using a remote dielectric sensor (ReDS), information that is provided to the clinician electronically. The ReDS wearable system received the CE (Conformité Européene) Mark in April 2014, and 510(k) Clearance from the US Food and Drug Administration (FDA) in August 2015; subsequently, the FDA designated the SMILE study as investigational device exemption exempt. Participants will be followed for a minimum of 3 months and a maximum of 9 months and compared with standard of care. The primary efficacy endpoint is the rate of heart failure readmissions during the follow-up period. Secondary endpoints include the time from discharge until the first heart failure readmission, the proportion of total days lost to hospitalization due to heart failure events, and the time from discharge until all-cause mortality. Quality of life will be evaluated by the Kansas City Cardiomyopathy Questionnaire and cost effectiveness using quality adjusted life years.

Eligible study participants will be aged at least 21 years with a clinical diagnosis of heart failure (regardless of ejection fraction), requiring hospitalization or within 10 days of follow-up from a heart failure admission. Elevated B-type natriuretic peptide (BNP ≥350 pg/mL within 24 hours of consent or ≥750 pg/mL at any time or N-terminal proBNP ≥1,400 pg/mL within 24 hours of consent or ≥3,000 pg/mL at any time). Key exclusions include: cardiac resynchronization therapy implant within 90 days prior to screening or planned implant during study duration, current or past pulmonary embolism in the right lung, severe pulmonary hypertension, ST-elevation myocardial infarction or coronary artery bypass graft within 30 days of enrollment, chronic renal failure with creatinine clearance <25 mL/min, chronic home IV therapy or inotrope, height <5′1″ or >6′4″, BMI <22 or >38 kg/m2, or severe chronic obstructive pulmonary disease on continuous home oxygen. As of late October 2016, approximately 100 patients of an anticipated 380 participants have been enrolled.

CONCLUSION

Efforts to improve and streamline the management of patients with chronic heart failure are anticipated to continue to receive a great deal of attention. The SMILE study is anticipated to improve our understanding of the potential role of remote monitoring in the management of heart failure.

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