Figure 5: Electrograms During Lateral Mitral Isthmus Ablation
Left: During left atrial appendage (LAA) pacing post endocardial lateral mitral isthmus ablation, coronary sinus (CS) activation is distal to proximal suggesting persistent conduction across the lateral mitral isthmus
Middle: During LAA pacing post additional ablation along the perceived endocardial course of the ligament of Marshall to the junction of the left pulmonary veins, the stimulus-to-electrogram interval on the CS electrodes has increased but the CS activation pattern appears fused with CS 5-6, CS 3-4 and CS distal activated almost simultaneously, suggesting slowed but persistent conduction across the lateral mitral isthmus
Right: During LAA pacing post additional ablation within the CS, the stimulus-to-electrogram interval on the CS electrodes increases further and the CS activation pattern is now clearly proximal to distal consistent with block across the lateral mitral isthmus