Although a major goal in the treatment of chronic
heart failure is to improve daily physical activity levels, this has not been assessed quantitatively. An increased daily activity level may be reflected by an increase in daily energy expenditure. In the present study, measurements of energy expenditure with a commercially available ambulatory calorimeter were first validated using cardio-pulmonary exercise tests in 5 normal volunteers. The energy expenditure measured by the calorimeter correlated well with that estimated from
oxygen uptake (r = 0.89). Subsequently, the daily energy expenditure was serially measured with the calorimeter during long-term administration of the converting
enzyme inhibitor ramipril for 24 weeks in 8 patients with chronic
heart failure. Changes in echocardiographic parameters and exercise capacity were also studied. Peak
oxygen uptake and anaerobic threshold assessed with symptom-limited maximal bicycle exercise were significantly increased 12 weeks or more after the initiation of treatment (P < 0.01 and P < 0.01, respectively). Left ventricular fractional shortening substantially, but not significantly, increased during this period (P < 0.1). These results strongly suggest that an overall improvement in
heart failure was achieved after long-term
ramipril therapy. The energy expenditure during daily activities was also significantly increased after
ramipril therapy for 24 weeks (P < 0.01). Thus, the daily energy expenditure increased with improvement of
heart failure, probably reflecting an increase in daily activity levels. We conclude that calorimetric measurement of daily energy expenditure is a novel and simple technique for quantitative evaluation of the effect of
therapy on daily physical activity levels in patients with chronic
heart failure.