Right-sided substrate eliminated by transmural ablation from the left atrial septum in a patient with atrioventricular nodal reentrant tachycardia

Key Teaching Points•Ablation in the left atrium is required when conventional right-sided ablation fails to eliminate typical or atypical atrioventricular nodal reentrant tachycardia (AVNRT) (∼1%).•Although left inferior extension of the slow pathway is considered a main reason for indispensable ablation of the inferior (posterior) part of the mitral annulus, the reasons and mechanisms for failure of right-sided ablation seem not to be focused on and may not have been adequately discussed in previous studies.•Even if a leftward extension of the slow pathway does not exist, left atrial ablation may be effective in eliminating the substrate of AVNRT to overcome the close proximity between the fast and slow pathways within the right atrium and the high risk of atrioventricular block. •Ablation in the left atrium is required when conventional right-sided ablation fails to eliminate typical or atypical atrioventricular nodal reentrant tachycardia (AVNRT) (∼1%).•Although left inferior extension of the slow pathway is considered a main reason for indispensable ablation of the inferior (posterior) part of the mitral annulus, the reasons and mechanisms for failure of right-sided ablation seem not to be focused on and may not have been adequately discussed in previous studies.•Even if a leftward extension of the slow pathway does not exist, left atrial ablation may be effective in eliminating the substrate of AVNRT to overcome the close proximity between the fast and slow pathways within the right atrium and the high risk of atrioventricular block.