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Characteristics of virtual unipolar electrograms for detecting isthmus block during radiofrequency ablation of typical atrial flutter

Yenn-Jiang Lin, MD^*, Ching-Tai Tai, MD^*,*, Jin-Long Huang, MD, Tu-Ying Liu, MD^*, Pi-Chang Lee, MD^*, Chih-Tai Ting, MD, PhD and Shih-Ann Chen, MD^*

^* Division of Cardiology, Department of Medicine, National Yang-Ming University School of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan
Taichung Veterans General Hospital, Taichung, Taiwan

View larger version (92K): [in a new window]   Figure 1 Complete cavotricuspid isthmus block during coronary sinus (CS) pacing after ablation. (A) After ablation, the activation wavefront originated in the CS ostium region blocked at the ablation line and propagated upward the septal wall. (B) The activation wavefront activated the roof and crossed the top of the crista terminalis. (C) The activation wavefront activated the high anterolateral wall and propagated downward. (D) The activation wavefront activated the low anterolateral wall and ended at the ablation line. The second component of virtual electrograms (virtual 6 to 10) at the ablation line showed an Rs pattern.

View larger version (74K): [in a new window]   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.

View larger version (82K): [in a new window]   Figure 3 Complete cavotricuspid isthmus (CTI) block and transcristal conduction during coronary sinus pacing after ablation. (A) The activation wavefront originated in the coronary sinus ostium (CSO) region and split into two wavefronts. (B) One wavefront propagated upward in the septal wall to the roof, and the other wavefront crossed the gap of the crista terminalis. (C) The upper wavefront crossed over the top of crista terminalis, and the lower wavefront activated the CTI opposite the pacing site. (D) The upper wavefront propagated downward in the anterolateral wall. The second component of virtual electrograms (virtual 10 to 12) showed an rSR pattern.