P6334Daily body weight in patients with chronic heart failure: improved diagnostic value by analysing prolonged time intervals

Background

Daily body weight (BW) is a mainstay in the management of patients with chronic heart failure (HF). Guidelines recommend to take action if BW increases more than 2kg within 3 days. However, the evidence behind the 2kg/3d rule is unclear and studies have shown poor diagnostic performance of this algorithm.

Purpose

To assess the diagnostic value of different BW thresholds and time intervals to alert for imminent HF decompensation.

Methods

We studied 184 patients with HF (age 71±10 yr, EF 26±11%). 43% had been hospitalized for HF during the preceding year. They were assessed by daily BW using digital scales with direct data transfer to a central data base. The mean follow-up was 286 days.

To decrease day-to-day variability, BW was analysed based on a daily moving average over 3 days. We retrospectively calculated the sensitivity and false-positive rate of BW thresholds at 1.5, 2.0, 2.5, 3.0 and 3.5 kg and time intervals between 2 and 30 days. Threshold crossings occurring within 30 days prior to a hospitalization for decompensated HF were deemed a positive alert.

Results

The sensitivity of 2kg/3d was poor (13%). Prolonging the time interval of weight changes markedly improved sensitivity. Increasing the weight threshold decreased the false positive rate. Greatest sensitivity (60%) was achieved using a 14 day interval at a weight threshold of 1.5 kg. However, this was associated with a high rate of false alerts (3.1 per patient/year). A weight threshold of 3.5 kg resulted in excellent specificity (0.3 false alerts per patient/year), however sensitivity was low (20%, 20 day time interval).

Conclusion

Monitoring daily BW using a 2kg/3d algorithm is associated with poor diagnostic performance. Generally, by analyzing stable trends over time (moving average) and using prolonged time intervals, BW monitoring with digital scales can achieve a clinically meaningful diagnostic performance. This new approach to BW monitoring may improve early detection of imminent HF decompensation.