RESUMO
INTRODUCTION: Endpoints confirming block in the critical isthmus in sinus rhythm and with pace mapping have not been established. METHODS AND RESULTS: A 44-year-old man with a history of Tetralogy of Fallot presented with recurrent ventricular tachycardia (VT). Entrainment mapping was consistent with a macroreentrant circuit rotating in a clockwise fashion under the pulmonic valve. After termination of the VT in a critical isthmus located on the conal free wall, a pace map proximal to the site of successful ablation was consistent with a change in QRS morphology. This change in QRS morphology suggested critical isthmus block and successful ablation, which was confirmed by noninducibility with programmed stimulation. CONCLUSION: Evidence of conduction block can be used as an additional endpoint for successful ablation of VT.
