title: The Impact of Lower-limb Heating on Exercise Capacity, Vascular and Metabolic function in patients with Heart Failure
Creators: name: Connolly, Joshua C
Publisher: name: Griffith University
Year: 2022
Subjects: subject: Heart failure
subject: lower-limb heating
subject: exercise capacity
subject: vascular function
subject: muscle metabolism

description: Heart failure (HF) − whilst primarily classified as an impaired ability to pump blood − also negatively impacts peripheral vascular function and blunts energy production (metabolism) in skeletal muscle. When combined, these factors result in a decreased exercise tolerance and, subsequently, a reduced quality of life. Recent studies have shown that lower-limb heating improves measures of vascular function in a healthy older population, and increases endurance capacity and vascular function in a peripheral artery disease population. However, the effects of lower-limb heating have never been studied in individuals with HF. The purpose of the study was to examine the impact of lower-limb heating on endurance exercise capacity, vascular function (blood flow and vascular tone) and muscle metabolism (skeletal muscle oxidation and tissue oxygen saturation) in individuals with HF. Thirteen individuals (71.3 ± 7.9 yrs) with heart failure with reduced ejection fraction (Ejection fraction, 31.6 ± 7.5 %) immersed both their lower-limbs into the bath - to a level just below the knee - for 45 minutes at either thermoneutral control (CON) (30°C) or hot (42°C) temperature (LLH). Femoral artery blood flow (Doppler ultrasound) was measured during immersion for both conditions. Postimmersion, individuals completed either an endurance shuttle walk test (ESWT) with a secondary outcome measure of peripheral tissue saturation index (TSI%, via Near-infrared spectroscopy) or alternatively, their arterial stiffness (pulse wave velocity) and peripheral muscle oxidative capacity was measured. Femoral blood flow velocity (193%), and subsequently, blood flow (270%) and mean shear rate (160%) increased continuously through LLH, whilst no improvement was noted in CON. Similarly, time to exhaustion (CON, 381.8 ± 57.3 s; LLH, 525.3 ± 60.5 s; p &lt; 0.01) and the total distance walked (CON, 603.9 ± 95.7 m; LLH, 816.2 ± 91.8 m; p &lt; 0.01) in the ESWT also increased in response to LLH. After LLH, TSI% was greater pre-ESWT when compared to CON (CON: 50.4 ± 1.6 %; LLH: 58.1 ± 1.6%), while TSI% converged to a similar nadir at end-ESWT for both conditions (CON: 44.8 ± 2.3 %; LLH: 46.6 ± 2.7 %). As a result, the ΔTSI% from pre- to end-ESWT was greater for LLH than CON (LLH, 10.7 ± 1.8 %; CON 4.44 Heart failure (HF) − whilst primarily classified as an impaired ability to pump blood − also negatively impacts peripheral vascular function and blunts energy production (metabolism) in skeletal muscle. When combined, these factors result in a decreased exercise tolerance and, subsequently, a reduced quality of life. Recent studies have shown that lower-limb heating improves measures of vascular function in a healthy older population, and increases endurance capacity and vascular function in a peripheral artery disease population. However, the effects of lower-limb heating have never been studied in individuals with HF. The purpose of the study was to examine the impact of lower-limb heating on endurance exercise capacity, vascular function (blood flow and vascular tone) and muscle metabolism (skeletal muscle oxidation and tissue oxygen saturation) in individuals with HF. Thirteen individuals (71.3 ± 7.9 yrs) with heart failure with reduced ejection fraction (Ejection fraction, 31.6 ± 7.5 %) immersed both their lower-limbs into the bath - to a level just below the knee - for 45 minutes at either thermoneutral control (CON) (30°C) or hot (42°C) temperature (LLH). Femoral artery blood flow (Doppler ultrasound) was measured during immersion for both conditions. Postimmersion, individuals completed either an endurance shuttle walk test (ESWT) with a secondary outcome measure of peripheral tissue saturation index (TSI%, via Near-infrared spectroscopy) or alternatively, their arterial stiffness (pulse wave velocity) and peripheral muscle oxidative capacity was measured. Femoral blood flow velocity (193%), and subsequently, blood flow (270%) and mean shear rate (160%) increased continuously through LLH, whilst no improvement was noted in CON. Similarly, time to exhaustion (CON, 381.8 ± 57.3 s; LLH, 525.3 ± 60.5 s; p &lt; 0.01) and the total distance walked (CON, 603.9 ± 95.7 m; LLH, 816.2 ± 91.8 m; p &lt; 0.01) in the ESWT also increased in response to LLH. After LLH, TSI% was greater pre-ESWT when compared to CON (CON: 50.4 ± 1.6 %; LLH: 58.1 ± 1.6%), while TSI% converged to a similar nadir at end-ESWT for both conditions (CON: 44.8 ± 2.3 %; LLH: 46.6 ± 2.7 %). As a result, the ΔTSI% from pre- to end-ESWT was greater for LLH than CON (LLH, 10.7 ± 1.8 %; CON 4.44 ± 1.6 %). LLH also tended to decrease peripheral pulse wave velocity and improve skeletal muscle oxidative capacity. Interestingly, a significant correlation (p &lt; 0.01) was observed between the relative change in the ESWT time in response to LLH and the initial shuttle walk test (ISWT) distance. The results from the present study suggest lower-limb heating potentially presents as a safe and cost-effective method to improve peripheral vascular function and function capacity in a HF population. 1.6 %). LLH also tended to decrease peripheral pulse wave velocity and improve skeletal muscle oxidative capacity. Interestingly, a significant correlation (p &lt; 0.01) was observed between the relative change in the ESWT time in response to LLH and the initial shuttle walk test (ISWT) distance. The results from the present study suggest lower-limb heating potentially presents as a safe and cost-effective method to improve peripheral vascular function and function capacity in a HF population.