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. 2022 Mar 18:13:825918.
doi: 10.3389/fphys.2022.825918. eCollection 2022.

Can Seismocardiogram Fiducial Points Be Used for the Routine Estimation of Cardiac Time Intervals in Cardiac Patients?

Zeynep Melike Işilay Zeybek  1 , Vittorio Racca  2 , Antonio Pezzano  2 , Monica Tavanelli  2 , Marco Di Rienzo  1
Affiliations

Can Seismocardiogram Fiducial Points Be Used for the Routine Estimation of Cardiac Time Intervals in Cardiac Patients?

Zeynep Melike Işilay Zeybek et al. Front Physiol. .

Abstract

The indexes of cardiac mechanics can be derived from the cardiac time intervals, CTIs, i.e., the timings among the opening and closure of the aortic and mitral valves and the Q wave in the ECG. Traditionally, CTIs are estimated by ultrasound (US) techniques, but they may also be more easily assessed by the identification of specific fiducial points (FPs) inside the waveform of the seismocardiogram (SCG), i.e., the measure of the thorax micro-accelerations produced by the heart motion. While the correspondence of the FPs with the valve movements has been verified in healthy subjects, less information is available on whether this methodology may be routinely employed in the clinical practice for the monitoring of cardiac patients, in which an SCG waveform distortion is expected because of the heart dysfunction. In this study we checked the SCG shape in 90 patients with myocardial infarction (MI), heart failure (HF), or transplanted heart (TX), referred to our hospital for rehabilitation after an acute event or after surgery. The SCG shapes were classified as traditional (T) or non-traditional (NT) on whether the FPs were visible or not on the basis of nomenclature previously proposed in literature. The T shape was present in 62% of the patients, with a higher ∓ prevalence in MI (79%). No relationship was found between T prevalence and ejection fraction (EF). In 20 patients with T shape, we checked the FPs correspondence with the real valve movements by concomitant SCG and US measures. When compared with reference values in healthy subjects available in the literature, we observed that the Echo vs. FP differences are significantly more dispersed in the patients than in the healthy population with higher differences for the estimation of the mitral valve closure (-17 vs. 4 ms on average). Our results indicate that not every cardiac patient has an SCG waveform suitable for the CTI estimation, thus before starting an SCG-based CTI monitoring a preliminary check by a simultaneous SCG-US measure is advisable to verify the applicability of the methodology.

Keywords: cardiac mechanics; heart failure; heart transplant; myocardial infarction; telemedicine; telerehabilitation.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
The seismocardiogram (SCG) signal, the localization of the fiducial points associated with the opening and closure of the aortic and mitral valve, its relation with the ECG waveform, and the schematization of how cardiac time intervals are derived. See text for abbreviations.
FIGURE 2
FIGURE 2
Scheme of the study.
FIGURE 3
FIGURE 3
SCG traditional (T) waveforms.
FIGURE 4
FIGURE 4
SCG non-traditional (NT) waveforms.
FIGURE 5
FIGURE 5
SCG T waveforms from 20 patients with the superimposition of the real location of MC, AO, AC, and MO events (in each panel represented in sequence by the black circles from left to right).
FIGURE 6
FIGURE 6
95% reference range of the differences observed in healthy subjects (continuous line), vs. the 95% range observed in the T population of patients (dashed line). Data are separately shown for each FP. Black circles indicate the mean value of each range.
See this image and copyright information in PMC

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