A Novel Criterion for Conduction Block After Catheter Ablation of Right Atrial Tachycardia After Mitral Valve Surgery

BACKGROUND: One operative approach to the mitral valve, the superior transseptal incision, is proarrhythmic because of extensive atriotomies. The objective of this study is to describe complex atrial tachycardias (ATs) that occur after this approach and propose methods to verify lines of block as an end point for catheter ablation. METHODS AND RESULTS: Of the 69 patients who had electrophysiological studies for AT after mitral valve surgery, 20 patients had prior superior transseptal incisions. Of these, 14 had complex ATs involving the lateral right atrium (RA). There were 9 dual-loop, 4 single-loop, and 1 focal tachycardias. Lateral wall ablation was performed either by creating a linear lesion from the lateral atriotomy to the inferior vena cava, superior vena cava, or tricuspid annulus or by ablating focally in the lateral RA. After a single ablation procedure, conduction block in the lateral wall was verified in 10 of 14 patients using 1 of 2 distinct patterns of block. One pattern consisted of late activation in an anterolateral corridor of the RA, and a second pattern consisted of wide-spaced double potentials. Recurrent conduction through the lateral wall lesions was associated with intraprocedural and late recurrences of ATs. CONCLUSIONS: The optimal end point for ablating ATs after mitral valve surgery with the superior transseptal approach is to establish lines of block that can be recognized by characteristic patterns of activation in the lateral RA. A novel criterion for lateral conduction block after catheter ablation is identification of a late-activated corridor in the anterolateral RA.