Diagnosis of dual accessory pathways by ajmaline test

In a patient with the Wolff-Parkinson-White syndrome, the existence of dual accessory pathways, both right-sided, was suspected during ajmaline test and confirmed during electrophysiologic study. The first accessory pathway was manifest in sinus rhythm while the second was obscured and revealed during low right atrial pacing. Ajmaline abolished conduction over the first pathway which most probably had a long refractory period allowing manifestation of the second pathway which had a very short refractory period. A longer conduction time over the second accessory pathway was suggested to explain its concealment during sinus rhythm.