Increased Susceptibility of the Heart to Ventricular Fibrillation During Metabolic Acidosis

Alterations of acid-base balance, clearly defined as metabolic or respiratory in origin, were produced in anesthetized dogs; ventricular fibrillation thresholds were determined during these conditions. During metabolic acidosis, we found that the heart became more susceptible to ventricular fibrillation, as indicated by a decrease in the ventricular fibrillation threshold value. During metabolic alkalosis, the threshold to ventricular fibrillation increased. In contrast, similar variations in pH owing to respiratory acidosis and alkalosis did not affect the ventricular fibrillation threshold. Hyperventilation in dogs with metabolic acidosis, even though resulting in alkaline arterial blood pH, did not protect the hearts from the increased susceptibility to ventricular fibrillation which existed as long as a base deficit was present. These results indicate that the heart is more susceptible to ventricular fibrillation during acidosis caused by metabolic factors and that primary variations in carbon dioxide tension have no such effect. Our study on dogs, under controlled conditions, provides experimental evidence in support of clinical experience which suggests that metabolic acidosis predisposes the heart to ventricular fibrillation.