Session PB6.7

Comparative Analysis of Infrasonic Cardiac Signals

K Tavakolian*, B Ngai, A Akhbardeh, B Kaminska, AP Blaber

Simon Fraser University
Burnaby, Canada

Signals such as ballistocardiogram (BCG), seismocardiogram (SCG) and apexcardiogram (ACG) belong to a category of mechanical cardiac signals in the infrasonic range (less than 20 Hz). They provide a noninvasive mechanical complement to the electrocardiogram and their ability to describe cardiovascular functionality is medically significant. Their characteristic complexes reflect the small-scale displacement, velocity, and acceleration of the body recoil in response to heart activity and blood flow. As such, they may be composed of and be indicative of either, or both, a myocardial vibration component and an arterial circulation component. Different techniques, or modalities, may be used to extract either component from the signal.
We are interested in the SCG complex as it relates to both myocardial vibration and arterial circulation and it can provide us information about both events.This research compares SCG recordings with two other widely reported modalities, the ultra-low BCG (ULF-BCG) and charge-sensitive force BCG, in order to better understand the SCG complex. The objective of this research is to understand different modalities used for recording of infrasonic cardiac signals and to establish their equivalences and differences in terms of capturing the underlying cardiovascular events. The findings of this research are further investigated with the echocardiogram as part of a parallel study.
The SCG signal is obtained with an accelerometer placed on the sternum to record the vibrations on the chest surface created by the heart. The classic displacement BCG complex is recorded from an original suspended ULF-BCG bed and the force BCG is obtained from an Emfit thin-film sensor which records the force created by the heart when the sensor is located underneath a supine subject. All three modalities are conducted as reported in the literature with same or similar sensing equipment. The parallel comparative analysis of the SCG with the echocardiogram has clarified the roles of the myocardial vibration and arterial circulation components in its complex. Here, the circulation component in the SCG also correlates well with the BCG, expected since the BCG traces the displacement of the body center of mass as blood is circulated in the arteries. In particular, the points of rapid systolic ejection and aortic valve closure could be identified on the SCG and BCG and are confirmed by echocardiogram. The Emfit sensor recordings also shows both components similar to the SCG.

(Abstract Control Number: 180)