Excitability curves of physiological and pathological dog auricle in the intact animal.

Abstract

Summary1. Three types of excitability curves of the dog auricle are described which were obtained by the method of permanent electrode implantation on either right or left auricle of the dog heart. 2. A normal curve can always be obtained within the first 12 hours after the operation. It consists of an absolute refractory period, a relative refractory period with a smoothly declining slope and a constant threshold level averaging 0.6 m. amp. 3. After 24 hours altered curves of two types appeared (a) one that showed a normal refractory period but a high diastolic threshold level. The elevated threshold was believed due to separation of the electrodes from the myocardium by fibrin deposit. (b) A curve with an abnormal refractory period as well as an elevated diastolic threshold. These latter were found to be associated with pathological changes in the myocardium under the electrodes as well as with the presence of epicardial fibrinosis.