New Concepts in the Approach to Digitalis Therapy for Atrial Fibrillation

¹ Cardiovascular Section, Department of Medicine, Hahnemann Medical College

It has been the purpose of this presentation to bring into sharp focus the precise electrophysiologic mechanisms that may be associated with atrial fibrillation. an approach to the interpretation of these serious cardiac mechanisms has been outlined. Irregularity of the ventricular rate in the presence of atrial fibrillation may be due to a combination of the following electrophysiologic events in the atrioventricular junction: (1) physiologic effective refractory period of the A-V node junctional tissues; (2) interference of subsidiary escape or accelerated A-V nodal pacemakers; (3) concealed A-V conduction in to the A-V junction; (4) entrance block into the A-V nodal tissues, and (5) exit block in the lower regions of the A-V nodal tissues.

Finally, digitalis should be withheld in the presence of independent activation of atria and ventricles due to advanced entrance or exit block, and accelerated nodal rhythm (70-130/min.) A trial of intravenous acetyl strophanthidin (0.5 mg.) may be required when the accelerated nodal rate is greater than 130/min., with intermittent periods of A-V dissociation.