Dual loop reentrant tachycardia with a combination of a localized reentry and a macro-reentry.

A 78-year-old woman presented 2 years after mitral valve replacement for rheumatic mitral stenosis with cardioversion-resistant atrial tachycardia (AT). Dual-loop AT was identified by activation mapping with the Rhythmia™ system (Boston Scientific, Marlborough, MA, USA) and confirmed by entrainment-mapping; one circuit with localized re-entry turned around the scar on the posterior left atrium and the other circuit, which was macro re-entrant, turned around the left superior pulmonary vein (LSPV) using the PV-carina, the ridge beween the left atrial appendage and the LSPV, and the roof. The two wavefronts fused on the posterior wall close to the LSPV. Radiofrequency ablation of an area of slow conduction on the posterior wall changed the tachycardia to roof-dependent AT which was then terminated by completion of a roof line. <Learning objective: In this case report, we demonstrate the importance of using both conventional entrainment mapping methods and a novel ultra-high density mapping system to precisely understand the mechanism and appropriately terminate the complex atrial tachycardia in patients with prior atrial fibrillation ablation.>.