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Figure 7 Left atrial horizontal position: pre-/postablation recordings, gross lesions and fluoroscopic image. The catheter was placed in a horizontal position superior to the mitral ring under the pulmonary veins (PV). Note the location of the coronary sinus catheter in relation to the ablation catheter. The distal and most proximal electrodes, 1 and 24, are both near the transeptal insertion site at the foramen ovale. The portion of the catheter positioned closer to the mitral ring (electrodes 7 to 13) recorded larger ventricular electrograms. The depolarization wavefront propagates from the septal region to the most distal recording within the left atrial appendage (LAA) in 50 ms. After radiofrequency ablation, the local electrogram amplitude decreased significantly. In addition, the recordings from electrodes 8 to 24 became fragmented, and the conduction time from the earliest to the latest electrode increased to 90 ms, 40 ms longer than preablation. These observations correspond to the linear contiguous lesions in the gross pathological photograph. MV = mitral valve.
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