A Comparison Of Myocardial Injury Between Monophasic And Biphasic Waveform Transthoracic Defibrillation

Objective: To compare the differences of myocardial injury between biphasic and monophasic waveform transthoracic defibrillation.Method: Thirteen healthly, adult and mongrel canines were randomly divided into monophasic waveform defibrillation group(n=7, A) and biphasic waveform defibrillation group(n=6, B). Ventricular fibrillation was induced electrically with catheter put through right external carotid vein into the right ventricle and defibrillation with the designated waveform and energy was performed after 15s. Changes of surface ECG lead II ST segment were recorded at 10s intervals for 30 s following termination of VF. Heart-type fatty acid-binding protein (H-FABP)concentration in peripheral blood before defibrillation and 0.5h,1h,2h after the restoration of sinus rhythm and cardiac troponin I (cTnI)concentration in peripheral blood before defibrillation and 4h,6h,8h after the restoration of sinus rhythm were measured by enzyme linked immunosorbent assay (ELISA); Cardiac pathological changes were observed after 72h.Result: In group A, ST segment depressed or elevated obviously in lead II electrocardiogram in 6 canines.In group B, ST segment depressed ramply in 1 canine, and returned to the baseline quickly, there was statistical significance between two groups(P=0.029). In both groups the level of H-FABP increased immediately after defibrillation, reached its peak time at 0.5h and declined thereafter. The level of H-FABP in group B was significantly lower than group A at 0.5h,1h (P <0.01) . However the level of H-FABP had no statistical significance after 2h (p> 0.05).The level of cTnI increased at 4h, and taken on upward trend , the level of cTnI in group B was significantly lower than group A at 8h (P <0.01). Compared with group A, pathological changes of cardiac injury significantly relieved in group B.Conclusion : Under the same defibrillation energy and number, the biphasic waveform defibrillation cause less severe myocardial injury than monophasic waveform defibrillation .