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NONINVASIVE ANALYSIS OF STROKE VOLUME VARIABILTY BY
RECORDING OF CARDIAC MECHANICAL VIBRATIONS ON THE CHEST
K. Tavakolian1, A.P. Blaber2, H.K. Symonds3, A. Akhbardeh4, W. Lee5,
B. Kaminska6
1
Engineering Science, 2Department of Biomedical Physiology and Kinesiology,
Simon Fraser University, 3Fraser Health Authority, Burnaby, BC, Canada, 4School of
Medicine, Johns Hopkins University, Baltimore, MD, USA, 5Burnaby General
Hospital, 6Engineering Science, Simon Fraser University, Burnaby, BC, Canada
Seismocardiography, SCG, is a method to record the mechanical vibrations created by
heart beating from the sternum, noninvasively. In this study an integrative approach is
presented to provide surrogate measures for beat-by-beat stroke volume variability
using SCG. Recordings of suprasternal pulsed Doppler was used as the reference
method for comparison. For each beat the stroke volume was determined by
multiplication of the area under the curve on the Doppler signal (stroke distance) with
the area of the aortic ring, LVOT. Morphological features were extracted from SCG
signal based on current knowledge of the correspondence of SCG waves to cardiac
events. Nonlinear methods were used to process these SCG features to produce an
estimate the stroke volume. For the control group eight healthy young subjects were
selected and the preliminary results, analyzed using Bland and Altman method,
showed that in 95% of the heart beats the stroke volume estimated by SCG was in a
7.5 mL range of the Doppler values. As our abnormal group we have considered ten
cardiac patients from the healthy heart program at Burnaby General Hospital who had
low ejection fractions. Recent studies have shown that analysis of stroke volume
variability can provide information about the inotropic state of the myocardium while
the older method of heart rate variability, HRV, provides us with knowledge of the
chronotropic state of myocardium and ventricular performance. SCG can provide us
with an inexpensive alternative method of monitoring of the cardiac contractility in
relation to electrocardiography.