Mitochondrial function and high energy compounds in myocardium during ventricular fibrillation

The purpose of this study was to learn the functional status of myocardial mitochondria and level of high energy compounds at different times after the onset of ventricular fibrillation in the absence of coronary perfusion and cardiac massage. Male Yorkshire swine were anesthetized with Halothane, intubated, ventilated and the exposed heart fibrillated by electric shock. Acceptor control ratios with glutamate, beta OH butyrate and succinate dropped only 5 to 10% in the first 5 min, but fell to 60% of normal by 10 min; mitochondrial 0₂ uptake values fell more rapidly. Lactic acid rose tenfold by 5 min and at 10 min showed a 16 fold increase. Creatine phosphate fell to 0 within 5 min, but ATP values fell only 50% in 5 min and rather slowly within the next 5 min. Myocardial cytochrome oxidase levels fell 25% in 5 min and 50% in 10 min. It was possible to electrically reestablish sinus rhythm with ease after 3 min but with difficulty after 5 in. While various biochemical alterations may cause this difficulty, loss of mitochondrial integrity does not appear to be a major factor.