Gyrocardiography: A Review of the Definition, History, Waveform Description, and Applications

Abstract

Gyrocardiography (GCG) is a non-invasive technique of analyzing cardiac vibrations by a MEMS (microelectromechanical system) gyroscope placed on a chest wall. Although its history is short in comparison with seismocardiography (SCG) and electrocardiography (ECG), GCG becomes a technique which may provide additional insight into the mechanical aspects of the cardiac cycle. In this review, we describe the summary of the history, definition, measurements, waveform description and applications of gyrocardiography. The review was conducted on about 55 works analyzed between November 2016 and September 2020. The aim of this literature review was to summarize the current state of knowledge in gyrocardiography, especially the definition, waveform description, the physiological and physical sources of the signal and its applications. Based on the analyzed works, we present the definition of GCG as a technique for registration and analysis of rotational component of local cardiac vibrations, waveform annotation, several applications of the gyrocardiography, including, heart rate estimation, heart rate variability analysis, hemodynamics analysis, and classification of various cardiac diseases.

Keywords: cardiac vibrations; cardiovascular diseases; gyrocardiography; health monitoring; signal processing; waveform description.

Figure 1

Simultaneous sample recordings of ECG, SCG (z-axis), GCG (y-axis), and phonocardiographic (PCG) signals captured in the supine position. The MC and MO waves in SCG and GCG correspond to mitral valve closure and opening; the AC and AO waves in SCG and GCG corresponded to the aortic valve closure and opening. S1 and S2 waves on PCG corresponded to mitral and aortic valve closure, respectively. EMD (electromechanical delay), PEP (Pre-ejection period), TST (total systolic time) and LVET (left ventricular ejection time) and systolic time intervals are also illustrated. The diagram is a modified version of the diagram originally published in the article by Dehkordi et al. in [42] with a GCG y-axis waveform derived from a diagram published in the work by Tadi et al. [11]. The cited works are available under the license CC-BY 4.0.

Figure 2

Raw SCG signal in three axes (left) and three orthogonal components of raw GCG signal (right). Typical axes of seismocardiogram (z-axis) and gyrocardiogram (y-axis) are shown as a red line. Modified version of the graph derived from the article [37] by Lee et al. under the license CC-BY 4.0.

Figure 3

SCG signal (left) and GCG signal (right) in three axes after applying Savitzky-Golay filter to remove motion artifacts. Typical axes of seismocardiogram (z-axis) and gyrocardiogram (y-axis) are shown as a red line. Modified version of the graph derived from the article [37] by Lee et al. under the license CC-BY 4.0.

Figure 4

(A) Typical GCG waveforms in the x, y, and z axis and reference ECG signal. (B) 3-axis ensemble averaged GCG signals. (C) GCG waveforms in the y-axis obtained using different sensors (Murata SCC1300d02, Bosch BMI 160, Maxim Integrated MAX21000, and the SONY Xperia Z3 compact). The graph derived from the article [11] by Tadi et al. under the license CC-BY 4.0.

Figure 5

An example of GCG y-axis and SCG z-axis inter-subject variation with various levels of signal quality (top to bottom: good, medium, low and very low). Adapted version of the graph derived from the article [11] by Tadi et al. under the license CC-BY 4.0.

Figure 6

The model of the relationship between the rotation of the horizontal plane $\alpha$ and angular velocity $\omega$.

Figure 7

The comparison of ECG, LV TDI and GCG y-axis with marked Sa, SPV, Ea and DPV. An excerpt of a diagram in the article by Tadi et al. [11] under the CC-BY 4.0 license.

Figure 8

Modified Wiggers diagram. A sample of the SCG signal in the dorso-ventral (z) axis is shown alongside other cardiovascular signals: the aortic pressure, atrial pressure, ventricular volume, electrocardiogram, and phonocardiogram. The mitral valve closure (MC) and opening (MO), and aortic valve closure (AC) and opening (AO) are labeled based on the pressure signals. Modified version of the diagram presented in the article by Taebi et al. [70] shared under the license CC-BY 4.0.

Figure 9

Waveform annotation in GCG x- and y-axis with corresponding time intervals and reference ECG. Modified version of the diagram by Tadi et al. published in [11] under the CC-BY 4.0 license.

Figure 10

Overall ECG (lead I), GCG and SCG waveform characteristics of normal (A), atrial fibrillation (B), and coronary artery disease with ischemic changes: T-wave inversion (C) and ST segment depression (D). The work by Iftikhar et al. [55] under the CC-BY 4.0 license.

Figure 11

An example of AFib and acute decompensated heart failure in cardiac signals. An excerpt of the diagram published in Mehrang et al. work [77] shared under the license CC-BY 4.0.