Experimental Study Of Early Echocardiography After Chest Burst Injury In Rabbits

Objective:To study the damage caused by the chest blast injury to the heart of experimental rabbits.The heart of the chest blast injury was observed by conventional echocardiography and two-dimensional speckle tracking imaging(2D-STI),in order to understand the characteristics of left ventricular changes after chest blast injury,to evaluate the changes of left ventricular function.The use of ultrasound technology to make a timely and accurate diagnosis of heart damage,to provide a clear imaging basis for the successful treatment of chest blast injury.Methods: Fifty healthy New Zealand white rabbits were randomly divided into injury group(45 rabbits)and normal group(5 rabbits).The rabbits in the injury group were randomly divided into three groups at different distances(14 cm,10 cm,6 cm)from the explosion source.The rabbits were placed in a specific blasting environment and were detonated in the chest area by instantaneous electric detonators at different distances to make animal models of light,moderate and severe chest blast injuries,and were respectively labeled A,B and C groups.Conventional echocardiography was performed on four groups of rabbits to observe the cardiac structure and function of the injury.Conventional echocardiographic parameter measurement: left ventricular fractional shortening(FS)was measured by M-mode ultrasound.The pulse wave Doppler(PW)was used to place the sampling point on the apex of the apical four-chamber coronal plane at the mitral valve orifice.The mitral valve peak-Tissue Doppler(TDI)mode,the sampling point on the mitral annular wall at the partition,measuring the maximum early diastolic velocity e,calculate and record the E / e ratio.Clearly recorded apical four-chamber heart section,the left ventricular end-diastolic volume(LVEDV),left ventricular end-systolic volume(LVESV),left ventricular ejection fraction(EF)and left ventricular stroke volume(LVSV)were calculated by Simpson's method.Each data is taken three times the average value measured.In 2D-STI mode were recorded and stored apex four-chamber heart,apical two-chamber heart,left ventricular long axis of view and short-axis view of the clear two-dimensional images,dynamic storage of 3-5 cardiac cycle two-dimensional images.The images were sent to a QLAB workstation and CMQ mode was selected for offline analysis.The left longitudinal global longitudinal strain(GLS)and the global circumferential strain(GCS)were analyzed and recorded.The longitudinal strain(Bas-GLS,Mid-GLS,Ap-GLS)and the circumferential strain(Bas-GCS,Mid-GCS,Ap-GCS)of each segment of left ventricular were measured.After the experiment,pathological examination was performed to observe the pathological features of myocardial injury.Results: 1.Conventional echocardiography results: A group of myocardial echo uniform,no significant segmental motor abnormalities.In group B,the movement of myocardial segments was less coordinated and the amplitude of activity was slightly weaker.In group C,some segments of myocardium were uncoordinated and the amplitude of activity was significantly decreased.A group of rabbits pericardial cavity no significant effusion.A small amount of pericardial effusion occurred in 3 rabbits in group B.C group of 11 experimental rabbit pericardial effusion.A group of eight rabbits showed mild mitral regurgitation.B group of 10 rabbits two,tricuspid valve moderate reflux,five experimental rabbit two,tricuspid valve appeared mild to moderate reflux.13 rabbits in Group C showed moderate and severe tricuspid regurgitation.The experimental rabbits in each group did not find obvious perforation of atrial septum and ventricular septum,rupture of free wall and so on.There were no significant differences in EF,EDV,ESV,SV,FS,E / e in group A compared with those in normal group(P> 0.05).The differences of EF,ESV,FS and E / e in group B were statistically significant Significance(P <0.05).There was no significant difference in EDV and SV between group B and control group(P> 0.05).The EF,EDV,ESV,SV,FS and E / e in group C were significantly lower than those in group C(P <0.05).Compared with group C,the differences of EF,ESV,FS and E / e in group A were statistically significant(P <0.05).A group of EDV,SV no significant difference(P> 0.05).The E / e in group B was significantly lower than that in group C(P <0.05).There was no significant difference in EF,EDV,ESV,SV and FS between group B and group C(P> 0.05).Compared with group A,the difference of ESV and E / e in group B was statistically significant(P <0.05).There was no significant difference in EF,EDV,SV and FS between group A and group B(P> 0.05).2.2D-STI parameters results: 2.1 Longitudinal strain of myocardial: Compared with the normal group,the Bas-GLS,Mid-GLS and GLS in group A decreased(P <0.05),while there was no significant difference in Ap-GLS between group A and normal group(P> 0.05).The LS and GLS of each segment in group B and C were lower than those in normal group(P <0.05).LS and GLS in segments A and B were significantly different from those in group C(P <0.05).The GLS?Bas-GLS and Ap-GLS in group B were lower than those in group A(P <0.05).There was no significant difference in Mid-GLS between groups A and B(P> 0.05).2.2 Circumferential strain of myocardium: Compared with normal group,Bas-GCS of group A was decreased(P <0.05),while there was no significant difference of Mid-GCS,Ap-GCS and GCS with normal group(P> 0.05),the CS and GCS in each group were significantly lower in group B and group C(P <0.05).There were significant differences in CS,GCS and C between the two groups(P <0.05).Ap-GCS in group B was lower than that in group A(P <0.05).There was no significant difference in GCS?Bas-GCS and Mid-GCS between groups A and B(P> 0.05).Conclusion: 1.Conventional echocardiography after moderate and severe chest detonation can be manifested as segmental wall movement disorders,pericardial effusion and cardiac dysfunction,etc,and light detonation injury heart morphology and function change is not obvious.2.2D-STI was used to assess the changes of LS and CS in some segments after chest burst injury,and LS was more sensitive than CS in the detection of myocardial abnormalities.3.2D-STI earlier than conventional echocardiography,sensitive diagnosis of left ventricular myocardial segment abnormalities.