Coexistence of functional Kent and Mahaim-type tracts in the pre-excitation syndrome. Demonstration by catheter techniques and epicardial mapping.

An unusual patient with Ebstein's anomaly of the tricuspid valve and the Wolff-Parkinson-White syndrome is presented. Ventricular pre-excitation related to conduction over both a right posterior Kent bundle and Mahaim fibers coursing from the atrioventricular node to the right ventricle. Two types of supraventricular tachycardia were demonstrable. These were due to re-entry involving antegrade conduction over either the normal or Mahaim paths, and retrograde retrograde conduction via the Kent bundle. Surgical division of the Kent bundle has abolished the clinically debilitating arrhythmias.