USE OF LIMB MOVEMENT SENSORS AS INDICATORS OF THE LEVEL OF EVERYDAY PHYSICAL-ACTIVITY IN CHRONIC CONGESTIVE-HEART-FAILURE

The level of everyday physical activity of patients with chronic congestive heart failure (CHF) may be an important reflection of their quality of life. Everyday physical activity is difficult to measure objectively, and may not relate to exercise capacity determined by laboratory exercise testing. A light-weight sensor worn on the wrist or ankle, which provides a cumulative record of limb movement, was evaluated. The sensor counted reliably when tested in a laboratory rig and during treadmill exercise. In 20 young normal subjects, hourly movement scores showed the expected diurnal rhythm. Twenty-four-hour movement scores in 30 patients with stable CHF were lower than in 20 age-matched control subjects (p <0.005). Movement scores in CHF correlated with a standard questionnaire scale assessing everyday physical activity (R = +0.72, p <0.001). Consecutive daily scores varied widely, but wrist and ankle scores were correlated (R >+0.7, p <0.05 in each subject), suggesting true day-to-day differences in activity rather than variability in the recording method. Recording for 5 to 6 consecutive days provides a reliable estimate of mean 24-hour movement score for a subject, and mean 24-hour scores were reproducible when subjects were retested after 8 weeks. There was a weak correlation between movement scores and exercise capacity as measured by peak oxygen consumption during maximal treadmill exercise (R = +0.42, p = 0.01). Quality-of-life score correlated with movement scores (R = +0.53, p <0.002) but not with peak oxygen consumption (R = +0.36; p = not significant). Thus, everyday physical activity as assessed by limb movement monitors is reduced in CHF. Level of everyday physical activity may be more relevant to the patient's quality of life than measurement of exercise capacity, and the movement monitors may be valuable to assess functional status and the response to therapies.