A Comprehensive Review on Seismocardiogram: Current Advancements on Acquisition, Annotation, and Applications

Abstract

In recent years, cardiovascular diseases are on the rise, and they entail enormous health burdens on global economies. Cardiac vibrations yield a wide and rich spectrum of essential information regarding the functioning of the heart, and thus it is necessary to take advantage of this data to better monitor cardiac health by way of prevention in early stages. Specifically, seismocardiography (SCG) is a noninvasive technique that can record cardiac vibrations by using new cutting-edge devices as accelerometers. Therefore, providing new and reliable data regarding advancements in the field of SCG, i.e., new devices and tools, is necessary to outperform the current understanding of the State-of-the-Art (SoTA). This paper reviews the SoTA on SCG and concentrates on three critical aspects of the SCG approach, i.e., on the acquisition, annotation, and its current applications. Moreover, this comprehensive overview also presents a detailed summary of recent advancements in SCG, such as the adoption of new techniques based on the artificial intelligence field, e.g., machine learning, deep learning, artificial neural networks, and fuzzy logic. Finally, a discussion on the open issues and future investigations regarding the topic is included.

Precordial Vibrations: A Review of Wearable Systems, Signal Processing Techniques, and Main Applications

“…Raw or pre-processed data from IMUs can be transferred to an end device for signal postprocessing via wireless or wired connection. For instance, in [ 63 ], all IMU and ECG measurements were simultaneously recorded and wirelessly transmitted via Bluetooth to a laptop, while, in [ 8 ], data were transmitted serially to a computer via USB cable using an Arduino Leonardo microcontroller. Otherwise, data can be stored locally using an onboard memory such as in [ 75 ], where all measurements from a six-degree-of-freedom IMU were stored on a memory card and processed later using custom-made software.…”

“…For what concerns contact-based methods, cardiac vibrations can be recorded from the thorax as accelerations and angular velocities using magneto-inertial units (i.e., by accelerometers and gyroscopes) or as local deformations using strain sensors (especially, fiber Bragg gratings—FBGs) [ 7 ]. According to the measurand, signals can be distinguished into a seismocardiogram (SCG), which generally results from the linear acceleration component of precordial motion, and the gyrocardiogram (GCG), which represents the rotational component of precordial motion [ 8 , 9 ].…”

“…BGH: Burnaby General Hospital 7. TC: Terminal Club 8. CEBS: "Combined measurements of ECG, Breathing, and Seismocardiogram" database.…”

A Soft and Skin-Interfaced Smart Patch Based on Fiber Optics for Cardiorespiratory Monitoring

“…Acoustic sensors such as microphones on the thorax have also been proposed for cardiorespiratory monitoring, but the interference between respiratory and heart sounds complicates the simultaneous estimation of RR and HR [ 33 , 34 ]. Other studies proposed inertial sensors, such as accelerometers and gyroscopes, placed on specific landmarks of the chest (e.g., xiphoid process and left sternum) to detect heart-induced accelerations (i.e., generally known as seismocardiogram—SCG—signals) and angular velocities (i.e., since 2015 referred to as gyrocardiogram—GCG—signals) originating on the chest surface [ 35 , 36 ]. Recently, this technology has also been proposed for cardiorespiratory monitoring, but it does not ensure yet high measurement accuracy, and the comfort is limited by its rigidness and low compliance with the skin [ 30 ].…”

Computer-Aided Detection of Fiducial Points in Seismocardiography through Dynamic Time Warping

“…Compared to the conventional quasi-synchronous alignment, DTW-based quasi-synchronous alignment eliminates the fiducial point detection error due to the stretching (or squeezing) manipulation. Compared to the envelope-based detection methods [ 14 , 18 , 19 , 20 ], DTW-based quasi-synchronous alignment does not limit to any specific fiducial points, as long as the corresponding cardiac events could be identified in an clinical imaging modality (not limited to echocardiogram, that was used in this paper) or cardiac signal that is simultaneously measured with ECG. This method has the potential to untie the knot that limits the development of SCG.…”