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[Research of myocardial velocity characteristics of paced canine heart based on ultrasonic Doppler tissue imaging].

OBJECTIVE
To quantitatively analyze the characteristics of regional myocardial velocities of paced heart over His bundle, and explore the myocardial velocity pattern.


METHOD
5 dogs were paced at 120 times/min over His bundle. We defined the His bundle adjacent region and the top region of interventricular septum (IVS) as our regions of interest (ROI). Images of Doppler tissue velocity in ROI and corresponding electrocardiograms were observed and recorded by a 2-D Color Doppler tissue imaging (DTI) system. Quantitative velocities of myocardial DTI images were mapped by a neural network from the image sequences. Finally the velocity characteristics of the myocardium around His bundle and IVS were analyzed.


RESULT
We obtained myocardial time-velocity curves in the ROI, and some results based on those curves: In the His bundle adjacent region intervals of myocardial systole and diastole were (209.75 +/- 19.41) ms and (294.50 +/- 17.87) ms, respectively. Myocardial systole velocity (S), early diastole velocity (E) and late diastole velocity (A) were (5.43 +/- 1.53) cm/s, (3.95 +/- 1.18) cm/s and (1.72 +/- 0.77) cm/s, respectively, E/A was 2.06 +/- 0.95; In IVS region intervals of myocardial systole and diastole were (191.33 +/- 17.23) ms and (294.70 +/- 17.91) ms, respectively. S, E and A were (3.17 +/- 1.34) cm/s, (2.17 +/- 0.64) cm/s and (1.48 +/- 0.52) cm/s, respectively. E/A was 1.305 +/- 0.287.


CONCLUSION
The primary characteristics of myocardial velocities paced over His bundle were: 1) Myocardial velocities in His bundle adjacent region were higher than those in IVS. 2) E/A was greater than one.