Relationship of Hypoxia to Arrhythmia and Cardiac Conduction Hemorrhage

The relationship between hypoxia, arrhythmia, and hemorrhage of the conducting system was studied in the experimental laboratory by rendering several different groups of rats and dogs hypoxic, and by the histological examination of the area of the atrioventricular node and bundle of His in sections obtained from the hearts of these animals. Sixty-one per cent of rats aged two weeks or older developed arrhythmias and had hemorrhage. None of 10 baby rats presented changes when submitted to the same type of experiment. Hemorrhage was present in only 40 per cent of asphyxiated dogs and in 40 per cent of the dogs that were made hypoxic during cardiopulmonary bypass; 75 per cent of dogs which underwent total mitral valvular replacement and expired in acute pulmonary edema 3 to 10 days postoperatively presented a similar type of lesion. In most cases, the administration of oxygen sufficed to reverse the electrocardiographic changes back to normal.Hypoxia is suggested as the primary cause for these changes, on the basis of previous clinical and experimental work and the information collected from these experiments. The importance of a possible species difference was suggested when attempts were made to correlate the results in rats, dogs, and humans.