On the heart vibrations: Some insights from ECG and laser doppler vibrometry.
De Lauro E., De Martino S., Falanga M.
V - Biofisica e fisica medica
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We have compared mechanical and electric hearth vibrations in safe males by adopting nonconventional and standard methods. Specifically we have measured the mechanical vibration of the thorax by means of non-contact, non-invasive laser Doppler vibrometer, whereas the electric features are measured by a traditional portable ECG. From a direct comparison between simultaneous measures, it is possible to observe that the mechanical vibrations retain all the main information held in the ECG. Indeed, the cycle RR is preserved and also the peaks associated with the S1 and S2. In addition, the mechanical vibration contains the detailed and specific information on the heart such as the typical cardiac frequencies of 12 and 15 Hz. By applying both linear and nonlinear methods, we derive that the mechanical vibrations can be decomposed into two separate, independent, nonlinear modes, whose dimension in terms of degrees of freedom is very low (two for the separate modes and three for the raw signal). They can be directly associated with the longitudinal and torsional modes of the heart. The separation into two time signals would allow researchers to highlight and to better study cardiac anomalies in more detail.