Effects of different resuscitation modalities on post-resuscitation myocardial apoptosis in porcine models of cardiac arrest

Abstract

Objective To confirm whether in post-resuscitation myocardial dysfunction involved in myocyte apoptosis mechanism in porcine model of cardiac arrest and apoptosis index varied from different modalities of cardiopulmonary resuscitation or not.Methods A total of 22 WZSP inbred small swine were randomly (random number) divided into sham operation group (SHAM) (n =6),defibrillation first group (DF,n =8) and chest compression first group (CF,n =8).Eight minutes after ventricular fibrillation was set up,standard CPR was carried out subsequently after defibrillation in porcine models of cardiac arrest in DF group and defibrillation after standard CPR in CF group,and hemodynamics were monitored.Twentyfour hours after restoration of spontaneous circulation (ROSC),animals were sacrificed,and myocardial specimens were examined with electron microscopy,Western blot,quantitative RT-PCR,and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay.The experimental data were analyzed by SPSS 17.0.Student's t test was employed for comparisons between two groups.Differences within groups at different time intervals were compared with repeated measures ANOVA.A two-tailed value of P ＜ 0.05 was considered statistically significant.Results Myocardial function was significantly impaired after ROSC.Levels of Bcl-2,Bax and caspase-3 protein was markedly increased in the CF and DF groups than those in the SHAM group (P ＜ 0.05) at 24 h after ROSC,while Bcl-2/Bax was significantly reduced in the CF and DF group compared with the SHAM group (P ＜ 0.05),and much more apoptotic cells were observed in cardiac arrest animals in comparison with sham-operation animals (P ＜ 0.05).Six hours after ROSC,hemodynamic indicators improved significantly in group DF than those in group CF,but Bcl-2,Bax and caspase-3 protein levels and apoptotic index were not significantly different bewteen the DF group and CF group (P ＞ 0.05).Conclusions Caspase-3-mediated apoptosis might be one of the main pathological mechanisms of postresuscitation myocardial injury in a porcine model of cardiac arrest,but there was no statistically significant difference in apoptosis index between two resuscitation modalities,showing no one modality was superior over another. Key words: Apoptosis; Cardiopulmonary resuscitation; Postresuscitation myocardial dysfunction; Casoase-3 ; Bcl-2/Bax