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Figure 2 Incomplete cavotricuspid isthmus (CTI) block during coronary sinus pacing after ablation. (A) The activation wavefront originated in the coronary sinus ostium region with splitting of two wavefronts. (B) One activation wavefront propagated upward in the anterior septal wall to the roof, and the other wavefront proceeded downward in the posteroseptal wall to the CTI. (C) The upper wavefront crossed over the crista terminalis, and the lower wavefront traveled through the CTI. (D) Both wavefronts collided in the low anterolateral wall. The second component of virtual electrograms (virtual 7 to 11) showed an rS pattern.