Leg Heat Therapy in Heart Failure With Preserved Ejection Fraction

Leg Heat Therapy to Improve Functional Performance in Heart Failure With Preserved Ejection Fraction (HFpEF)

The objective of this pilot study is to establish evidence to support the validity of HT in improving skeletal muscle function and physical capacity of patients with HFpEF. Our central hypothesis is that HT treatment will lead to improvements in skeletal muscle and microvascular function compared to a control intervention. As a result, we anticipate that patients treated with HT will demonstrate improved skeletal muscle microvascular blood flow and oxygenation resulting in enhanced exercise tolerance. To explore this hypothesis, we propose the following specific aim: Explore the effects of home-based HT on exercise tolerance in patients with HFpEF.

Study Overview

• Status: Recruiting
• Conditions: Heart Failure With Preserved Ejection Fraction
• Intervention / Treatment: Device: Leg heat therapy; Device: Leg sham therapy

• Study Type: Interventional
• Enrollment (Estimated): 90
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Daniel Hirai, PhD; Phone Number: 765-494-7113; Email: dhirai@purdue.edu
• Study Contact Backup: Name: Doris Muriathiri, MPH, CCRP; Phone Number: 317-274-0903; Email: dmuriath@iu.edu

Study Locations

• United States
  • Indiana
    • Indianapolis, Indiana, United States, 46202
      • Recruiting
      • IU Health University Hospital
      • Contact: Doris Muriathiri, MPH, CCRP; Phone Number: 317-274-0908; Email: dmuriath@iu.edu
    • Indianapolis, Indiana, United States, 46202
      • Recruiting
      • IU Health Methodist
      • Contact: Doris Muriathiri, MPH, CCRP; Phone Number: 317-274-0903; Email: dmuriath@iu.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Men and women older than 18 years
• Established diagnosis of heart failure with preserved ejection fraction (HFpEF) including left ventricular ejection fraction (LVEF) ≥50% as evidenced by Doppler echocardiography and/or ratio of the early mitral inflow velocity (E) to septal tissue Doppler velocity (e') >8 and at least 1 other sign of chronically elevated filling pressures, including an enlarged left atrium (left atrial volume index >34 mL/m2), an elevated N-terminal pro-brain natriuretic peptide (NT-pro-BNP) level within the past year, long-term loop diuretic use for control of symptoms, or elevated filling pressures (mean pulmonary capillary wedge pressure >12 mmHg) on prior cardiac catheterization
• Stable medical treatment

Exclusion Criteria:

• Recent hospitalization (within the previous 1 month)
• Unstable angina and/or uncontrolled cardiac arrhythmia causing symptoms or hemodynamic compromise (including severe bradycardia or tachycardia, sick sinus syndrome, or multifocal premature ventricular contractions)
• Presence of any clinical condition that makes the patient unsuitable to participate in the trial, e.g., significant ischemic or valvular heart disease, cor pulmonale, unstable coronary artery disease, primary renal (e.g., estimated glomerular filtration rate (eGFR) <25 mL/min/1.73 m2) or hepatic disease (e.g., aspartate aminotransferase and alanine aminotransferase levels >3.0 times the upper limit of the normal range), pulmonary, neuromuscular, orthopedic disorders, among others
• Inability to exercise on the treadmill
• Inability to provide informed consent
• Concern for inability of the patient to comply with study procedures and/or follow up (e.g., alcohol or drug abuse)
• Any contraindication to heat therapy and/or inability to fit into water-circulating trousers
• Impaired thermal sensation in the leg

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Heat therapy; Patients will be provided with water-circulating trousers, a water heater, and a water tank coupled to a water pump. The heater will be adjusted to warm up the water to 42ºC. Participants will be asked to apply the therapy daily for 90 min while in the supine position.	Device: Leg heat therapy; A sous vide heating immersion circulator heats up the water inside the water tank to 42ºC. A water pump circulates temperature-regulated water through the trousers.
Sham Comparator: Sham control; Patients will be provided with water-circulating trousers, a water heater, and a water tank coupled to a water pump. The heater will be adjusted to warm up the water to 33ºC. Participants will be asked to apply the therapy daily for 90 min while seated or in the supine position.	Device: Leg sham therapy; A sous vide heating immersion circulator heats up the water inside the water tank to 33ºC. A water pump circulates temperature-regulated water through the trousers.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in time to exhaustion during treadmill exercise	The investigators will determine whether daily leg heat therapy for 90 min using water-circulating trousers perfused with water heated to 42ºC improves the time to exhaustion during treadmill exercise testing at 2-month follow-up compared to a sham treatment.	Baseline to 2-month follow-up

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in maximal pulmonary oxygen uptake during treadmill exercise	Maximal pulmonary oxygen uptake (VO2max) will be evaluated during treadmill exercise testing. The investigators will determine whether leg heat therapy improves VO2max at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in triceps surae microvascular oxygenation during treadmill exercise	Microvascular oxygenation will be assessed using near-infrared spectroscopy (NIRS) during treadmill exercise testing. The investigators will determine whether leg heat therapy improves muscle microvascular oxygenation at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in systolic blood pressure	The systolic blood pressure will be measured in triplicate using a blood pressure monitor. The investigators will determine whether leg heat therapy improves systolic blood pressure at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in diastolic blood pressure	The diastolic blood pressure will be measured in triplicate using a blood pressure monitor. The investigators will determine whether leg heat therapy improves blood pressure at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in Minnesota Living with Heart Failure Questionnaire (MLHFQ) score	Health-related quality of life will then be assessed via the MLHFQ, which is a validated, self-administered, 21-item disease-specific instrument for patients with heart failure. Items are scored in a 6-point Likert scale (0 to 5) and reflect physical, emotional and socioeconomic status during the past 4 weeks. The questionnaire is scored by summation of all 21 responses (with higher scores indicating poorer quality of life).	Baseline to 2-month follow-up
Change in triceps surae microvascular oxygenation during reactive hyperemia	Microvascular oxygenation will be assessed using near-infrared spectroscopy (NIRS) during reactive hyperemia. The investigators will determine whether leg heat therapy improves muscle microvascular oxygenation at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in triceps surae volume	The volume of calf muscles will be determined using magnetic resonance (MR) images. The investigators will determine whether leg heat therapy improves calf muscle volume at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in triceps surae intramuscular fat content	The intramuscular fat content of calf muscles will be determined using magnetic resonance (MR) images. The investigators will determine whether leg heat therapy reduces intramuscular fat content at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in the time constant for phosphocreatine recovery after dynamic exercise	Magnetic resonance spectroscopy tuned to phosphorous (31PMRS) will be used to measure the time constant for PCr recovery (τ) after dynamic planar flexion exercise. The investigators will determine whether leg heat therapy reduces the time constant for PCr recovery at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up
Change in maximal plantar flexor strength	The maximal voluntary contraction (MVC) strength of the plantar flexor muscles will be assessed using an MR-compatible ergometer. Participants will be asked to perform three plantar-flexor MVCs separated by a one-minute rest period. The MVC torque will be considered the highest peak torque value measured over the three trials. The investigators will determine whether leg heat therapy improves maximal plantar flexor strength at 2-month follow-up compared to the sham treatment.	Baseline to 2-month follow-up

Collaborators and Investigators

• Sponsor: Indiana University
• Collaborators: Purdue University

Study record dates

Study Major Dates

• Study Start (Actual): August 15, 2024
• Primary Completion (Estimated): August 20, 2026
• Study Completion (Estimated): August 31, 2026

Study Registration Dates

• First Submitted: April 24, 2024
• First Submitted That Met QC Criteria: April 24, 2024
• First Posted (Actual): April 29, 2024

Study Record Updates

• Last Update Posted (Actual): November 17, 2025
• Last Update Submitted That Met QC Criteria: November 13, 2025
• Last Verified: November 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Cardiovascular Diseases; Heart Diseases; Heart Failure
• Other Study ID Numbers: IRB # 16143

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: Yes
• product manufactured in and exported from the U.S.: Yes