THE ACTION OF CARDIAC GLYCOSIDES ON THE REFRACTORY PERIOD OF HEART TISSUES

¹ Department of Physiology and Pharmacology, National Institute of Cardiology, México, D. F.

The action of two cardiac glycosides, digitoxin and ouabain, were studied as to their effect on the refractory period of the auricle, ventricle and auriculoventricular propagation tissue in the dog heart under different experimental conditions.

These cardiac glycosides decreased the refractory period of the auricular muscle when this tissue maintained its vagal innervation and an appropriate method of anesthesia was used. In the denervated heart or heart-lung preparation, these cardiac glycosides increased considerably the refractory period of the auricular muscle.

The refractory period of the auriculo-ventricular propagation tissue was progressively increased to the point of complete auriculo-ventricular block.

These cardiac glycosides, in doses within what is considered the therapeutic range, decreased the refractory period of the ventricular muscle. In the toxic phase, the refractory period of the ventricular muscle continued to decrease until exposed to concentrations close to those which would initiate ventricular fibrillation.

The mechanisms by which digitalis decreases the ventricular rate in auricular fibrillation are discussed.

The need is pointed out for referring to the specific action of these pharmacological agents on specific physiological properties of the different tissues of the heart, and not to generalize for the whole heart results obtained on one tissue.

This article has been cited by other articles:

				H. S. Friedman, M. Win, A. Hussain, and A. Sinha Effects of Cardiac Glycosides on Atrial Contractile Dysfunction After Short-term Atrial Fibrillation Chest, October 1, 2000; 118(4): 1116 - 1126. [Abstract] [Full Text] [PDF]