The Ultrasonic Integrated Strain Study Of Healthy Beagle's Left Ventricle During Cardiac Pacing

Objective: To integrally and accurately evaluate biomechanical characteristics of left ventricular(LV) wall we used the ultrasonic integrated strain(IS) timed sequence which is established by a somewhat more involved derivation using radial strain(RS) timed sequence, circumferential(CS) timed sequence, and longitudinal strain(LS) timed sequence during different states: baseline (BASE) and the right ventricular apex pacing (RVAP), the left ventricular apex pacing (LVAP), the left ventricular lateral wall pacing (LVLP) states.Method: Eight healthy Beagle dogs underwent echocardiographic scanning for the research. The dynamic gray-scale images of the left ventricle in 3 complete cardiac cycles were acquired respectively during baseline (BASE) and pacing at the right ventricular apex (RVAP), the left ventricular apex (LVAP) and the left ventricular lateral wall (LVLP) states in three short-axis views and three long-axis views. The segmental sub-endocardial and sub-epicardial mechanical parameters of LV including RS, CS and LS timed sequence, were derived from dynamic gray-scale images using a dedicated VVI workstation. The segmental sub-endocardial and sub-epicardial mechanical parameters of integrated strain(IS) timed sequence was established using a formula :IS=√RS~2+CS~2+LS~2.Results: (1) The results of the qualitative observation: IS-time curve could be produced with the RS, CS and LS time timed sequences in which the trend of IS could be observed. We could find out that the absolute value of IS was higher than the absolute value of CS, RS OR LS at most point-in-time from the IS-time curve.(2) The results of the quantitative analysis:①The amount of segments of statistically significant PIS in BASE as opposed to 3 cardiac pacing states was much more than the amount of segments of statistically significant PCS, PRS or PLS in BASE as opposed to 3 cardiac pacing states(P<0.05);②To be compared with the PIS in BASE and in 3 cardiac pacing states: The segmental sub-endocardial PIS in BASE was statistically significant higher than those opposed to the sub-endocardial PIS of correspond segments in 2 or 3 states of LVAP, LVLP and RVAP, except middle-lateral wall(P<0.05);The segmental sub-epicardial PIS in BASE was statistically significant higher than those opposed to the sub-epicardial PIS of correspond segments in 1 to 3 states of LVAP, LVLP and RVAP, except base inferior, lateral, middle lateral, and apical anterior wall(P<0.05);Conclusion:The integrated strain results of the left ventricle which is based on velocity vector imaging technique hint that: the biomechanical characteristics of left ventricular wall is a complex performance system. The derivation of endocardial and epicardial integrated strain timed sequence of left ventricular wall could be established, which open a new approach to evaluate the biomechanical characteristics of left ventricular wall properly. IS maybe be a new parameter for more precise evaluation of the biomechanical characteristics of left ventricular wall.