Efficacy of cardiac rehabilitation with motion assistance from wearable cyborg hybrid assistive limb in patients with chronic heart failure: a randomized controlled trial

Abstract

Background: Recent Cochrane Systematic Review suggested that the participation in cardiac rehabilitation is associated with approximately 20% lower cardiovascular mortality and morbidity. Exercise therapy is the key component of cardiac rehabilitation programs. In recent years, innovative technologies have been introduced into the field of rehabilitation, and a typical example is the wearable cyborg Hybrid Assistive Limb (HAL). The wearable cyborg HAL provides motion assistance based on detection of bioelectrical signals on the skin surface when muscle forces are generated. The lumbar‐type HAL is expected to expand the therapeutic options for severe cardiac patients who have difficulty in performing usual cardiac rehabilitation programs, such as bicycle pedaling or walking. Purpose: We aim to compare the efficacy of exercise therapy performed with motion assistance from a lumbar‐type HAL versus conventional training (sit‐to‐stand exercise without HAL) in patients with chronic heart failure. Methods: This clinical trial is a randomized, non‐blinded, and controlled study. Twenty‐eight heart failure patients (73.1±13.8 years) who have difficulty in walking at the usual walking speed of healthy subjects were randomly assigned to 2 groups (HAL group or control group) with a 1:1 allocation ratio and performed sit‐to stand exercise either with HAL or without HAL for 5 to 30 minutes once a day, and 6 to 10 days during the study period. The brain natriuretic peptide (BNP), isometric knee extensor strength, standing ability (30‐seconds chair‐stand test: CS‐30), short physical performance battery (SPPB) and 6‐minute walking distance (6MWD) were measured before and after the completion of cardiac rehabilitation. Cardiac events such as death, re‐hospitalization, myocardial infarction and worsening of angina pectoris and heart failure during 1 year after discharge were evaluated. Results: There was no significant difference in the number of days of exercise therapy between the two groups. BNP, SPPB and 6MWD were improved in both groups. In the HAL group, the isometric knee extensor strength (0.29±0.11 vs 0.35±0.11 kgf/kg, p=0.003) significantly improved and CS‐30 (5.5±5.1 vs 8.2±5.3, p=0.054) tended to improve. However, in the control group, either the isometric knee extensor strength (0.35±0.11 vs 0.36±0.14 kgf/kg, p=0.424) or CS‐30 (6.0±4.3 vs 9.2±6.2, p=0.075) did not significantly change. HAL group showed significantly more improvement in the isometric knee extensor strength than control group (p=0.045). Cardiac events occurred in 20% in the HAL group and 43% in the control group. Conclusion: The improvement in isometric knee extensor strength with the assistance from lumbar‐type HAL suggests that exercise therapy using this device may be useful in chronic heart failure patients with flail or sarcopenia, a strong poor prognostic factor in these patients.