| Summary: | Objective To investigate the change of left ventricular systolic function in rabbits at low temperature by using two-dimensional speckle-tracking technique. Methods Thirty New Zealand rabbits were randomly and equally divided into control group, hypothermia for 4 h(group A) and for 8 h(group B) groups. After routine cardiac measurements were performed firstly, then tissue Doppler imaging (TDI) was carried out to record peaks in the S, E and Aspectra of the septal side of the mitral valve, followed by speckle-tracking imaging (STI) to obtain global peak longitudinal strain (SL), circumferential strain (SC) and radial strain (SR), and the peak values in the basal, medium and apical segments. The indexes of myocardial enzyme spectrum were detected by hematology, and the changes of myocardial pathology were observed by HE staining. Results Significant differences were seen in the conventional ultrasound parameters, such as left ventricular end-systolic diameter (LAESd), left ventricular end-diastolic diameter (LVEDd), left ventricular ejection fraction (LVEF), peak systolic velocity (Sm), peak early diastolic velocity (Em), and peak end diastolic velocity (Am) between the control group and group B(P < 0.05). Compared with the control group, the global SL, SC and SR and the values in apical segment were obviously decreased in group A, and the above global values and those in basal, medium and apical segments were all reduced in group B(P < 0.05). The global SL and SR values and those in the 3 segments were notably lower in group Bthan group A(P < 0.05). The serum levels of aspartate aminotransferase (AST), creatine kinase (CK), creatine kinase isozyme (CK-MB), and high-sensitivity cardiac troponin T(HS-TNT) were significantly increased in groups Aand Bthan the control group (P < 0.05). HE staining showed that partially broken myocardial fibers, disintegrated cardiomyocytes, dissolved nuclei, lightly stained chromatin, and Alot of inflammatory cells were seen in group B. Conclusions With the extension of low temperature time, the myocardial tissue shows damage at different degrees. Two-dimensional speckle-tracking technology can find declined left ventricular function earlier than LVEF and TDI.
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