The Spatiotemporal Correlation Between Cardiac Electrical And Mechanical Activity Based On Intracardiac Tissue Doppler Ultrasonic Imaging

Cardiovascular disease is the leading cause of human death. Disordered cardiac electrical and mechanical activity resulting from various cardiovascular diseases makes the heart failed to pump blood. A better understanding of the spatiotemporal correlation between 'cardiac electrical and mechanical activity could lead to deep understanding of mechanism of cardiac disease, efficient diagnosis and treatment of arrhythmias, and optimal design of artificial pacemaker. But because of the complexity of this problem itself and the limited research means, it remains a problem in cardiac electrophysiology.A new approach based on intracardiac ultrasonic tissue Doppler imaging and image analysis for the study of the correlation was proposed and applied to sinus and paced canine hearts. The spatial information of tissue mechanical motion was ensured by the experienced selection of imaging direction and imaged object; the quantitative mechanical motion information was extracted though the tissue Doppler image analysis; and the synthesized cardiac electrical activity information was obtained from synchronously recorded body surface electrocardiogram. Then the spatiotemporal correlation between the regional tissues of sinoatrial node (SAN), His-bundle (HB) and left ventricle (LV) was investigated.Firstly, a new image analysis based method quantitatively extracting tissue acceleration and velocity from ultrasound tissue Doppler color image was developed. Combining color component decomposition and artificial neural network, this method could be used to separated anatomical and tissue Doppler information; therefore, anatomical information could be reserved while extracting mechanical motion information of cardiac tissue, as was vital in the study of the correlation.Secondly, after successfully imaging SAN and observing the anatomical structure and mechanical activation procedure in vivo with a newly developed intracardiac catheter, mechanical activation pattern of the tissue of SAN was portrayed and its temporal correlation with ECG phase was characterized. Furthermore, during HB pacing, the activation pattern of the tissue around HB was investigated, and the mechanical activation time, which was define in this thesis as the interval between the beginning of the local mechanical activation around HB and the full activation of ventricles, was calculated. The similarity of the patterns of SAN and HB implies the feasibility to map the cardiac electrical activity with tissue Doppler acceleration imaging.Finally, for sinus, right ventricle (RV) paced and HB paced canine hearts, tissue Doppler velocity image sequences of LV tissue were acquired. A method was developed to calculate strain rate (SR) and to form SR image from 2D tissue Doppler velocity image. By comparing the SR vs. time curve and the correlation induced by the three different cardiac electrical stimuli, it was founded that the regional deformation rate of LV during HB pacing is much more similar to that during sinus pacing than that during RV pacing. It suggests new information for optimal pacemaker design and assessment of pacing effect.