Digitalis in the pre-excitation syndrome. Analysis during atrial fibrillation.

The effect of digitalis in 21 patients with Wolff-Parkinson-White syndrome was anlayzed with respect to the ventricular response during atrial fibrillation and antegrade and retrograde refractory periods of accessory pathways. Digitalis shortened the cycle length of the most rapid ventricular response (shortest R-R) (i.e., increased the ventricle response) in 6/21 patients, increased the cycle length in 7/21 patients, had no effect on the cycle length in 5/21, and could not be determined in 3/21. Digitalis could be directly related to the onset of ventricle fibrillation resulting from atrial fibrillation in 9/21 patients. Each of these patients had shortest R-R intervals (220 msec or less) during atrial fibrillation in the control data. The results of this study indicate that no a priori prediction about the effect of digitalis on the antegrade conduction of accessory pathways can be made. By elective induction of atrial fibrillation it is possible to separate WPW patients into groups at high and low risk for developing ventricular fibrillation with the administration of digitalis.