Association of an accessory atrioventricular pathway and ipsilateral bundle branch block.

We performed electrophysiological study and radionuclide phase imaging in a patient with intermittent Wolff-Parkinson-White syndrome type A and left bundle branch block. The presence of a left-sided accessory pathway was proven by eccentric retrograde atrial activation. Phase-imaging revealed delayed left ventricular phase angles when left bundle branch block was present in the electrocardiogram. There was an advance of early phase angles at the ventricular insertion of the accessory pathway as well as delayed phase angles in the rest of the left ventricle when the pre-excitation pattern was seen electrocardiographically.