The appearance of ventricular preexcitation during exercise testing reproduced by dobutamine administration.

A 33-year-old woman presented with exercise-related palpitations after an apparently successful catheter-ablation of overt midseptal accessory pathway. Post procedure, the electrocardiogram at rest was normal, while the progressive appearance of delta-wave during treadmill stress testing was recorded. In addition, the occurrence of ventricular preexcitation was reproduced by controlled administration of dobutamine. Detailed understanding of the unusual pathway electrophysiology resulted in specific planning of the second procedure. In the basal state, pacing maneuvers did not demonstrate any evidence of pathway conduction. However, during infusion of dobutamine bidirectional conduction in the right anterior pathway was restored, enabling definitive cure by radiofrequency.