Effect of Digitalis on Atrioventricular Conduction and Circus-Movement Tachycardias in Patients with Wolff-Parkinson-White Syndrome

During regular driving of the right atrium using the single-test stimulus method, atrioventricular conduction and initiation of tachycardias were studied in six patients with the Wolff-Parkinson-White syndrome (W-P-W), before and 45 min after the administration of ouabain (0.75-1.5 mg into the right atrium). Following ouabain (1) all patients showed shortening of the refractory period of their anomalous pathway; (2) at least five of them showed lengthening of the refractory period of the A-V nodal-His pathway; and (3) all patients showed prolongation of the A-V nodal transmission time (prolongation of the A-H interval). In four patients who suffered from circus-movement tachycardias these changes resulted in two patients in marked shortening of the range of premature beat intervals during which a tachycardia could be initiated and complete inability to initiate a tachycardia in the other two. These results suggest that digitalis can be of prophylactive value in patients with the Wolff-Parkinson-White syndrome and circus-movement tachycardias.