Atrial linear ablations in pigs. Chronic effects on atrial electrophysiology and pathology.

BACKGROUND: Generation of long and continuous linear ablations is required in a growing number of atrial arrhythmias. However, deployment and assessment of these lesions may be difficult, and there are few data regarding their short- and long-term effects on atrial electrophysiology and pathology. METHODS AND
RESULTS: A nonfluoroscopic mapping and navigation technique was used to generate 3-dimensional (3D) electroanatomic maps of the right atrium in 8 pigs. The catheter was then used to deliver sequential radiofrequency (RF) applications (power output gradually increased until 80% reduction in the amplitude of the unipolar electrogram) to generate a continuous lesion between the superior and inferior venae cavae. The animals were remapped 4 weeks after ablation during septal pacing. Lesion continuity was confirmed in all cases by the following criteria: (1) activation maps indicating conduction block [significant disparities in activation times (52.0+/-16.0 ms) and opposite orientation of the activation wave front on opposing sides of the lesion], (2) evidence of double potentials (interspike time difference of 52.3+/-17.1 ms), and (3) low peak-to-peak amplitude of the bipolar electrograms (0.7+/-0.6 mV) along the lesion. At autopsy, all lesions were continuous and transmural, averaged 50.5+/-6.7 mm, and were characterized histologically by transmural fibrosis throughout the length of the lesion.
CONCLUSIONS: Long linear atrial ablation, created by sequential RF applications (using unipolar amplitude attenuation as the end point for energy delivery), results in long-term continuous and transmural lesions. Lesion continuity is associated with evidence of conduction block in the 3D activation maps and the presence of double potentials and low electrogram amplitude along the lesion.