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Figure 5 Left atrial activation maps acquired during tachycardia in Patient 6, who had a left atriotomy. (A) Posteroanterior (PA) projection, which demonstrates a re-entrant loop around an area of low voltage in the posterior wall. (B) Anteroposterior (AP) view of the same tachycardia, demonstrating a second limb of the circuit involving the mitral annulus. A bystander region is present between the mitral annulus and an area of low voltage in the septum with wavefront collision (double lines). MV = mitral valve.