SPONTANEOUS INCESSANT AV REENTRANT TACHYCARDIA RELATED TO LEFT-BUNDLE-BRANCH BLOCK AND CONCEALED LEFT-SIDED ACCESSORY AV PATHWAY

Three patients in whom permanent AV reentrant tachycardia became the c linical manifestation of Wolff-Parkinson-White syndrome are described. The substrate for the arrhythmia was created by coexistence of a conc ealed left-sided accessory pathway and an ipsilateral bundle branch bl ock. Pharmacologic therapy in all three patients failed to control the tachycardia, which in two cases led to severe left ventricular failur e. After successful radiofrequency ablation of the accessory pathway ( in two) or AV junction (in one), left ventricular function gradually r eturned to normal.