[The effect of ouabain on sinus node function and intracardiac conduction (author's transl)]

The effect of 0.5 mg Ouabain (O) i.v. on sinus node function and on intracardiac conduction was studied by His bundle electrography and atrial stimulation. 7 patients with normal sinus node function and av conduction (group I), 5 patients with sick sinus syndrome (group II), and 5 patients with av block of changing degree (group III) were examined. 2 additional patients had simultaneous sinus node dysfunction and av block (group II/III). The sinus node recovery time was prolonged in 6 patients, the av block was located proximal to the His bundle in 4 patients and distal to the His bundle in 3 patients. The spontaneous sinus rate decreased in group I and remained unchanged in group II and III after O. The PA interval increased slightly after O in groups II and III, the AH interval during sinus rhythm was prolonged after O in groups II and III and in the whole group together. During atrial pacing, the stimulus-His-time was increased in each group when compared at identical stimulation rates. In 4 of 7 patients av block type Wenckebach appeared at a lower stilmulation rate after O. The HV interval remained unaltered after O, the sinus node recovery time varied after O. Phenytoin had no positive effect on the changes observed after O. Unwanted actions of O such as increased bradycardia or increased av conduction disturbances were not observed. O appears to be reasonably safe in most patients with sick-sinus syndrome and changing av block.