Ballistocardiography for Ambulatory Detection and Prediction of Heart Failure Decompensation

Abstract

Background Ambulatory home monitoring of heart failure (HF) patients (pts) to assess clinical status remotely and adjust therapies accordingly could potentially decrease the costs associated with hospitalizations and improve pts quality of life. Our group has been investigating the use of non-invasive ballistocardiogram (BCG) measurements (the measurement of body vibrations due to cardiac ejection of blood) using a modified weighing scale for monitoring hemodynamics and cardiac timing intervals from HF pts. BCG waveforms from HF pts in a decompensated state will show, on average, a higher variability in signal structure than corresponding waveforms from pts in a compensated state. Methods For each of the 36 HF pts included in the study, we recorded simultaneously daily 30-second measurements of electrocardiogram (ECG) and BCG signals using a modified weighing scale ( Fig. 1 a). Recordings were processed for data quality and some of the waveforms were discarded if data quality was insufficient (e.g. missing R-peaks in ECG signals). We developed a metric from the BCG signal that quantifies the variability of the BCG heartbeat waveforms ( Fig. 1 b). Results Of the 36 pts (83% men, 58 ± 13 years, left ventricular ejection fraction 0.31 ± 0.12, New York Heart Association functional class I/ II 36% and III 64%), 18 pts were recorded only when hospitalized for a HF exacerbation, 11 were recorded in the outpatient setting, and 7 were recorded both during a hospitalization for HF exacerbation and in the outpatient setting. Pts were considered decompensated (day of hospital admission) or compensated (day of hospital discharge or outpatient visit) based on the clinician assessment. We found that the BCG variability was significantly different between the groups based on pts state: compensated (n=648 recordings) 0.46 ± 0.013 and decompensated (n=223 recordings) 0.54 ± 0.026, p=0.002 ( Fig. 1 c). Conclusion BCG variability, a metric of consistency defined quantitatively based on the shape of BCG signals, can be captured using a modified weighing scale. BCG variability is significantly different between decompensated and compensated HF pts. This metric may be used in future studies for detection of HF worsening in ambulatory pts at home.