| PurposeLow temperature can cause a certain degree of damage to human organs and tissues,but low temperature has little effect on myocardial damage.In this study,two-dimensional spot tracking technology was applied to evaluate the change rule of left ventricular myocardial injury in rabbits with time under low temperature,which not only provided a non-invasive method for the evaluation of left ventricular myocardial injury in workers and guards under low temperature,but also provided a detailed experimental basis for relevant studies.MethodsThirty healthy New Zealand rabbits were selected,male or female,body weight 3-3.5kg,and randomly divided into three groups,the control group and the low-temperature groups A and B,10 in each group.The control group was placed at a room temperature of 22-25 ° C,and the low-temperature groups A and B were placed in a freezer at-25 ~30° C for 4h and 8h,respectively.Use8% barium sulfide to remove rabbit body and limb hair,and use medical tape to fix 5 layers of gauze and cotton on the experimental rabbit(heat preservationeffect),put it in the freezer,leave a certain gap in the freezer to ensure the experimental rabbit Required oxygen.With GE Vivid 7 color ultrasound imaging system,10 s probe(10MHz),all rabbits were anesthetized with sodium pentobarbital(1.5%,2ml/kg),connected to the synchronized electrocardiogram,left lying position,conventional echocardiography The left ventricle diameter at the end of systole(LAESd)and the left ventricle diameter at the end of diastole(LVEDd)were measured.Biplane Simpson method was used to measure left ventricular ejection fraction(LVEF).TDI records the mitral annulus septal lateral motion spectrum,and measures the systolic motion velocity(Sm),early diastolic motion velocity(Em),and late diastolic motion velocity(Am).Collect two-dimensional dynamic images of the four,three,and two-cavity hearts at the apex,and two-dimensional dynamic images of the basal,middle,and apical segments in the left ventricular short axis,each with 5 cardiac cycles,and offline into the Echo PAC workstation for analysis.Select a clear two-dimensional image,manually outline the endocardium,adjust the diameter of the region of interest to the satisfaction of each segment,obtain the SL,SC,SR and curves of the myocardium of each segment,record the overall and horizontal longitudinal peak strain(SL),Peak radial strain(SR)and circumferential strain peak(SC),and then record the peak systolic longitudinal strain rate(Sr L S),early diastolic longitudinal strain rate(Sr L E),late diastolic longitudinal strain rate(Sr L A)Peak radial strain rate(Sr R S)during systole,peak radial strain rate(Sr R E)during early diastole,peak radial strain rate(Sr R A)during late diastole,peak peripheral strain rate(Sr C S)during systole,early diastole The peak circumferential strain rate(Sr C E)and the peak post-diastolic circumferential strain rate(Sr C A)were all averaged over 5cardiac cycles.Five rabbits in each group were randomly selected and subjected to femoral arterial and venous puncture under ultrasound guidance.Blood samples were taken for detection of serum aspartate aminotransferase(AST),serum phosphocreatine kinase(CK),and Enzymes(CKMB),high-sensitivity troponin T(HS-TNT).After ultrasound examination and blood sampling,the experimental rabbits were euthanized by air embolization of the ear veins.The left ventricular anterior papillary muscles and wall myocardium were taken for fixation,dehydration,embedding,sectioning and HE staining.ResultCompared with the control group,the basal segment,middle segment,apical segment and overall levels SL,Sr L S,Sr L E,and Sr L A in the low-temperature group B were statistically significant(all P <0.01);the basal segment and the middle segment in the low-temperature group B,Apical segment and overall level SL,Sr L S,Sr L E,Sr L A are statistically significant(all P <0.01);basal segment,middle segment,apical segment and overall level SC,Sr C S,Sr C E,low temperature group B Sr C A and SR,Sr R S,Sr R E,and Sr R A are statistically significant(all P <0.05);the overall level SL,apical level SL,overall level Sr L S,overall level Sr L E,overall level Sr L A in the hypothermic A group,Basal level Sr L A,intermediate level Sr L E,intermediate level Sr L A,apical level Sr L S,apical level Sr L E,apical level Sr L A,overall level SC,apical level SC,overall level Sr C S,overall level Sr C E,overall Level Sr C A,basal level Sr C E,basal level Sr C A,apical level Sr C S,global level SR,apical level SR,global level Sr R S,global level Sr R E,global level Sr R A,basal level Sr R A,intermediate level Sr R E,intermediate level Sr R A,apical level Sr R S,apical level Sr R A differences were statistically significant(all P <0.05).With the extension of low temperature time,the shape of longitudinal strain curve is gradually flat and the peak value is delayed.Compared with the control group,the differences in LAESd,LVEDd,LVEF,Sm,Em,and Am in the low-temperature group B were statistically significant(all P <0.05);compared with the control group and the low-temperature group A,the differences in LAESd and LVEF All have statistical significance(all P<0.05).Compared with the control group,there was no statistically significant difference in LAESd,LVEDd,LVEF,Sm,Em,and Am in the hypothermic A group(all P> 0.05).Compared with the control group,the AST,CK,CK-MB,HS-TNT of the low-temperature A and B groups were all increased,and the increase of the low-temperature B group was obvious,with significant statistical significance(P <0.01);compared with the low-temperature A group In comparison,the AST,CK,CK-MB,and HS-TNT of the low-temperature group B all increased,with significant statistical significance(all P <0.01).In this experiment,the overall left ventricular level SL was negatively correlated with AST,CK,CKMB,HS-TNT,with statistical significance(r = 0.851,P <0.01;r = 0.852,P <0.01;r = 0.841,P <0.01;r = 0.842,P <0.01).ConclusionThe application of 2d-sti technology can accurately evaluate the degree of left ventricular myocardial injury in low temperature environment,which is of great significance for guiding clinicians to conduct timely intervention treatment. |
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