Outcome of prolonged ventricular fibrillation and CPR in a rat model of chronic ischemic left ventricular dysfunction

Cardiopulmonary resuscitation ameliorates myocardial mitochondrial dysfunction in a cardiac arrest rat model

PURPOSE

Previous studies implicate that the mitochondrial injury may play an important role in the development of post-resuscitation myocardial dysfunction, however few of them are available regarding the ultrastructural alterations of myocardial mitochondria, mitochondrial energy producing and utilization ability in the stage of arrest time (no-low) and resuscitation time (low-flow). This study aimed to observe the dynamic changes of myocardial mitochondrial function and metabolic disorders during cardiac arrest (CA) and following cardiopulmonary resuscitation (CPR).

METHODS

A total of 30 healthy male Sprague-Dawley rats were randomized into three groups: 1) VF/CPR: Ventricular fibrillation (VF) was electrically induced, and 5 min of CPR was performed after 10 min of untreated VF; 2) Untreated VF: VF was induced and untreated for 15 min; and 3) Sham: Rats were identically prepared without VF/CPR. Amplitude spectrum area (AMSA) at VF 5, 10 and 15 min were calculated from ECG signals. The rats' hearts were quickly removed at the predetermined time of 15 min after beginning the procedure to gather measurements of myocardial mitochondrial function, high-energy phosphate stores, lactate, mitochondrial ultrastructure, and myocardial glycogen.

RESULTS

The mitochondrial respiratory control ratios significantly decreased after CA compared to sham group. CPR significantly increased respiratory control ratios compared with untreated VF animals. A significant decrease of myocardial glycogen was observed after CA, and a more rapid depletion of myocardial glycogen was observed in CPR animals. CPR significantly reduced the tissue lactate. The mitochondrial ultrastructure abnormalities in CPR animals were less severe than untreated VF animals. AMSA decayed during untreated VF; however, it was significantly greater in CPR group than the untreated VF group. In addition, AMSA was clearly positively correlated with ATP, but negatively correlated with myocardial glycogen.

CONCLUSION

Impairment of myocardial mitochondrial function and the incapability of utilizing glycogen were observed after CA. Furthermore, optimal CPR might, in part, preserved mitochondrial function and enhanced utilization of myocardial glycogen.

A Rat Model of Ventricular Fibrillation and Resuscitation by Conventional Closed-chest Technique

A rat model of electrically-induced ventricular fibrillation followed by cardiac resuscitation using a closed chest technique that incorporates the basic components of cardiopulmonary resuscitation in humans is herein described. The model was developed in 1988 and has been used in approximately 70 peer-reviewed publications examining a myriad of resuscitation aspects including its physiology and pathophysiology, determinants of resuscitability, pharmacologic interventions, and even the effects of cell therapies. The model featured in this presentation includes: (1) vascular catheterization to measure aortic and right atrial pressures, to measure cardiac output by thermodilution, and to electrically induce ventricular fibrillation; and (2) tracheal intubation for positive pressure ventilation with oxygen enriched gas and assessment of the end-tidal CO2. A typical sequence of intervention entails: (1) electrical induction of ventricular fibrillation, (2) chest compression using a mechanical piston device concomitantly with positive pressure ventilation delivering oxygen-enriched gas, (3) electrical shocks to terminate ventricular fibrillation and reestablish cardiac activity, (4) assessment of post-resuscitation hemodynamic and metabolic function, and (5) assessment of survival and recovery of organ function. A robust inventory of measurements is available that includes - but is not limited to - hemodynamic, metabolic, and tissue measurements. The model has been highly effective in developing new resuscitation concepts and examining novel therapeutic interventions before their testing in larger and translationally more relevant animal models of cardiac arrest and resuscitation.