Algorithm for automatic detection of the cardiovascular parameter PR-interval from LDV-velocity signals

Laser-Doppler-vibrometry (LDV) is broadly employed in mechanical engineering but it has been demonstrated by several researchers that the technique has also large potential in biomedical applications. In particular, the detection of several vital parameters (heart rate, heart rate variability, respiration period) is known as optical vibrocardiography - VBCG. Recent studies have demonstrated the possibility of a reliable detection of the PR-interval (time between atria and ventricle contractions) and classification of the different types of atrioventricular (AV) blocks from this velocity signals. In this work, an algorithm for the localization of the vibrations generated by atrial contraction for the detection of the PR-interval in VBCG acquired on the thorax is presented. The determination of the time point of a heart beat can be extracted easily because it generates an unambiguous maximal velocity peak in the time data. Extracting the contraction of the atrium is more challenging because it is a characteristic signature with an amplitude at the magnitude of the signal disturbances. We compare different approaches of a cost function for the determination of the time point of the atria-contraction signature as well as different optimization algorithms to find the correct PR-time.