Physical Activity Assessed with Accelerometer is an Accurate and Independent Predictor of Mortality in Patients with Advanced Heart Failure

Abstract

BackgroundIt is generally acknowledged that in the population as whole, larger volumes of physical activity and a high physical capacity is associated with longevity. In heart failure, physical capacity expressed as peak VO2, is one of the most, robust prognostic factors established. Recent work has put forward the volume of physical activity in daily life as a relevant prognostic aspect in heart failure. Patients with heart failure often display a distinct pattern of walking characterized of short step‐length and frequent short pauses. In the present study we test if this 1) can be assessed using accelerometers and 2) can be used in a prognostic model.Methods: 60 patients with advanced heart failure (NYHA III, peak VO2 <20 ml/kg and LVEF <35%) underwent exercise test with peak VO2, echocardiography and routine chemistry. Daily activity was assessed by an accelerometer worn attached to the waist during waking hours for 7 consecutive days. Mortality over 5‐years was 52%. The analysis focused on episodes with high‐recorded activity, which was identified by calculating a rolling mean. From these episodes information on average activity was calculated along with measures of variance. Cox proportional hazards regression was used to analyze the data.Results: Peak activity variance was strongly and independently correlated with mortality and increased accuracy when added to peak VO2 and the Heart Failure Survival Score prognostic model.ConclusionPeak activity variance is a promising novel prognostic marker in heart failure and it is a measure of physical activity independent of physical capacity.