Experimental Study Of Applying Velocity Vector Imaging In Diagnosing Pigs With Myocardial Contusion

ObjectiveTo investigate whether the role of velocity vector imaging (VVI) was superior than 2DE in qualitative diagnosing pigs with myocardial contusion(MC);Further to estimate the role of VVI in clinical application of early diagnosis of myocardial contusion and quantitative evaluation of left ventricular systolic function.MethodsEight pigs were selected and wounded to creat an animal model with MC by a small striker. Siemens Sequoia 512 ultrosound imaging system and a 2.5～4.25 MHz probe were applied to collect and analyze the images. Before MC and 0.5,2,4,8 h after MC, the images of the standard LV short-axis views at the levels of mitral annulus, papillary muscle and apex, and the apical four chamber, two-chamber and long-axis view of LV in three consecutive cardiac cycles of the acquired loops were collected and saved as two-dimensional dynamic gray-scale images and the model of VVI. Then, these images were transferred to VVI work station for off-line analysis. Under the condition of two-dimensional gray-scale images, the abnormalities of the wall motion were observed before and after MC. The endocardial markers were manually select at the midpoint of each segment, and the software automatically tracked every point endocardium. According to vector length, direction and torsion, the wall motion abnormalities were determined, which were finally compared with general pathological staining and triphenyl tetrazolium chloride (TTC) staining. Velocity, strain and strain rate curve was obtained. Furthermore, peak systolicε, SR of all segments of left ventricular at the levels of papillary muscle were measured in three consecutive cardiac cycles of the acquired loops. Finally, the average ofε, SR in three consecutive cardiac cycles were calculated and the change ofε, SR were compared in each segments of left ventricular before and after MC.ResultsAfter MC,2DE showed the abnormalities of segmental wall motion, and VVI displayed the ribbon deformation and the variance between vector length and direction. It showed that 56 segments were confirmed injured by general pathological staining in 128 segments. At 0.5,2,4,8 h after impaction there was no statistic significance in sensitivity between VVI and 2DE(P>0.05). But specificity of VVI was higher than that of 2DE, and there was statistic significance between them (P<0.05). After analysis by ROC, VVI showed bigger area than 2DE within each segment. Meanwhile, the results had statistic significance at 2,4,8 h after the injury (P<0.05). Compared with the value of baseline, peak racialεand SR after MC were lower (P<0.05); injury site were lower with normal site (P<0.05). The peak of systolicεand SR of all segments in left ventricular had no significant difference before MC(P>0.05).ConclusionVector length and direction of change can be visually displayed the abnormalities of segmental wall motion after MC. VVI was more obvious and intuitive than 2DE in observing the abnormalities of segmental wall motion, and which was expected to be a new, imple and rapid method in evaluation of MC.εand SR, as quantitative indexes, can sensitively reflect the systolic function of left ventricular region. Since VVI can quantitatively evaluate MC changes in wall motion more accurately and stably than 2DE, which was expected to become a new method in the early diagnosis of MC.