Quantification of cardiac kinetic energy and its changes during transmural myocardial ischemia assessed by multi-dimensional seismocardiography

Abstract

Abstract Background The third law of Newton implies that if one body exerts a force on a second body, the latter exerts a force equal in magnitude and opposite in direction on the first body. This reaction to heart and blood motion elicits low frequency vibrations transmitted to the chest surface. Multi-dimensional seismocardiography (SCG) assesses these linear and rotational accelerations by means of micro-accelerometers and micro-gyroscopes. From the linear and rotational acceleration signals, kinetic energy (KE) and its temporal integration (iK) can be computed as scalar parameters, both in a linear (iKLin) and in a rotational (iKRot) dimension. Evidence demonstrate that acute myocardial ischemia (AMI) profoundly affects the SCG waveform amplitude and that unidimensional SCG is accurate for the determination of acute coronary syndrome (ACS). Whether and how AMI affects multidimensional SCG signals is unknwon. Purpose AMI upon left anterior descendent coronary artery (LAD) occlusion markedly depresses iKLin and iKRot. Methods The protocol was in accordance with the principles of laboratory animal care. After 20 minutes of steady-state, anesthetized Landrance pigs underwent a percutaneous mid-LAD occlusion by means of intra-coronary balloon inflation for 90 min., followed by deflation and reperfusion (RE). SCG was recorded at baseline (BSL), upon LAD occlusion (AMIt0), after 60 min of occlusion (AMIt60), at the onset of LAD reperfusion (REt0) and after 60 min of recovery (REt60). iKLin and iKRot were computed from the amplitudes of SCG waveforms. iKLin and iKRot were calculated during the systolic and diastolic phases of the cardiac cycle (iKSys and iKDia, respectively). Firedman's ANOVA was used to test the trend of the above variables throughout the protocol, followed by Wilcoxon paired tests. Data are presented as median [IR]. Results Of the 21 investigated pigs, 3 died before protocol termination as a result of AMI complications and 4 had ruled out during the signal processing because of technical reasons. Considering the rotational variables, when compared to baseline, iKRot_Sys decreased by 17% both at AMIt0 (p=0.05) and AMIt60 (p=0.02); by 38% and 49% at REt0 and t60 (respectively, p<0.001). Similarly, iKRot_Dia decreased by 64% and 59% at AMIt0 and AMIt60 (respectively, p<0.02), and by 74% at REt0 and REt60 (both p=0.002). Considering the linear variables, iKLin_Sys decreased by 19% and 34% at AMIt0 and AMIt60 (respectively, p<0.04), by 39% and 53% at REt0 and REt60 (respectively, p<0.02). iKLin_Dia decreased by 42% at AMIt60 (p=0.03) and by 67% at REt60 (p=0.005) compared to baseline but did not change at the other time points (figure 1). Conclusions AMI depresses profoundly cardiac kinetic energy as recorded by multidimensional SCG. Thus, this nonintrusive and operator independent tool may prove useful in the detection of AMI and provide considerable opportunities for remote non-intrusive monitoring of cardiac functions. Funding Acknowledgement Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Fonds Erasme, FNRS_Fonds National Recherche Scientifique, Fonds pour la Chirurgie Cardiaque, PRODEXA