Changes of cardiac function and myocardial ultrastructure after crush injury in rabbits

Objective To explore the mechanism of myocardial secondary injury and cardiac dysfunction after crush injury in rabbits. Methods Forty-two New Zealand rabbits were randomly divided into control group (6 rabbits) and crush injury group (36 rabbits that received pressure of 20kg for 6h), and crush injury group were subdivided into instant group, 6, 12, 24, 48 and 72h group after pressure relief with 6 rabbits in each group according to pressure relief time. The cardiac function changes in different time periods were detected by the multi-functional composite echocardiography, and the myocardial ultrastructural changes in different time periods were observed under electron microscope. Results The systolic indexes such as left ventricular ejection fraction (EF), left ventricular circumference shortening (CS), ventricular wall thickening and cardiac output per minute and diastolic function indexes such as peak flow velocity during rapid filling phase, peak flow velocity during slow filling phase, E/A ratio and diastolic filling rate were progressively reduced at respective time points after pressure relief, especially EF and CS. All the indexes for cardiac function were reduced to negative peak level 12-24h after pressure relief (P < 0.01); the myocardial ultrastructural changes were obvious, particularly 24h after injury. Conclusions Crush injury may result in secondary injury to the myocardium and cardiac dysfunction, and the peak phase of cardiac injury was during 12-24h after pressure relief. Multi-functional composite cardiac echocardiography can accurately, objectively and rapidly assess the myocardium damage after crush injury.