Abstract: During the defibrillation of monophasic and bipliasic in 30 pigs, three methods for the e-valuation of myocardial injury were used：pathological examination, defibrillation electrocardiogram recording，and creatine phosphokinase （CPK） and CPK-MB detection before and after defibrillation. Through visual observation and microscope examination, monophasic and biphasic shocks may cause endocardial edema, thrombosis, localized fragmentation of myocardium and retrograde changes. But the result in biphasic shock was better than monophasic’s. Soft myocardium and endocardium with thrombi was detected in 4 pigs （9-12 shocks,20-50J）. Fragmentation of myocardium was observed in the surface of 5 pigs’ defibrillation （5 shocks, 360J）. In the biphasic and monophasic defibrillation, retrograde changes were detected in 2 pigs.ST-T seg-ment changed in electrocardiogram in 4 pigs and blockade appeared between ventricle and auricle in 2 pigs after monophasic shock. In biphasic shock，2 pigs and 1 pig obtained respectively. Be-cause CPK and CPK-MB varied in large range,the dates were not evaluated. This results suggest that the biphasic shock cause lower myocardial.injury than monophasic shockdo,with heat and electricity as possible causative factors. When the total energy is same，the defibrillation with high energy and little times can cause bigger myocardial injury than the defibrillation with low energy and more times；the injury may be healed.

Key words: Biphasic shock , Defibrillation , Myocardial injury , Pathologic examination , Electrocardiogram recording