Effect of Hypothermia on Experimentally Produced Arrhythmias

The effect of hypothermia on experimentally produced rapid arrhythmias in the dog was studied. Rapid ectopic rhythms were produced in open-chest and "intact" animals by application of aconitine solution to the right atrial wall. In all experiments, a beneficial cardiac effect was obtained: marked slowing of the ventricular rate occurred in all cases, and in approximately half of the cases sinus rhythm was restored. On rewarming, although the heart rate increased, the sinus rhythm acquired during hypothermia persisted in most instances. The blood pressure fell when a rapid arrhythmia was produced. A further drop was observed in approximately half the cases during hypothermia. In the remaining cases no change, or a slight rise in blood pressure, occurred during cooling. The results obtained in the experimental animal would appear to have a bearing on the therapy of certain refractory arrhythmias in the human subject.