A nonreentrant arrhythmia due to a dual atrioventricular nodal pathway.

A 33-year-old woman presented with an atypical arrhythmia. The electrophysiologic study revealed dual atrioventricular nodal pathways. The difference in conductivity of these tracts enabled simultaneous atrioventricular conduction with a double ventricular response to a single atrial impulse. This disturbance is uncommon. Lack of awareness of the existence of dual nodal pathway can cause diagnostic difficulties and therapeutic errors.