Variation of QRS morphology of premature ventricular contractions originate from the left-ventricular outflow tract during ablation.

Idiopathic ventricular arrhythmias originating from the aortic sinus of Valsalva often show preferential conduction to the right-ventricular outflow tract, which may render radiofrequency ablation more difficult. We describe a patient with symptomatic premature ventricular contractions of left-ventricular outflow tract origin presenting with a variation of QRS morphology during ablation. The correlation between the characteristics of local voltage potentials and the real origin site of the ventricular arrhythmia is discussed.