Background Aortic dilatation was frequently observed in patients with atrial fibrillation (AF) and non-pulmonary vein (PV) triggers are important for mapping and ablation of AF. We hypothesized that the aortic encroachment area over left atrium (LA) could contribute to the local substrate characteristics. Methods We studied 32 consecutive patients of AF (age = 57.34 ± 8.07, male = 30), including 26 paroxysmal and 6 persistent AFs. Anatomic relationship between LA and aorta, and electrophysiological characteristics of the encroachment areas were investigated. IRB approval was taken. Results The LA bipolar voltage (mean 0.49 ± 0.26 mV) was lower at aortic encroached area compared to global LA (mean 1.52 ± 0.48 mV) and it was statistically significant (p < 0.001). There was a linear correlation between the voltages of LA and distance from the aorta to the aortic encroachment area of LA (p < 0.001, R = 0.616). Non-PV triggers were observed in 34.37% (n = 11) of total patients. The initiation of AF in aortic encroached area was seen in 45.45% (n = 5) of non-PV trigger and 15.62% of total patients. All the patients were followed up for 6 months and 4 (14.81%) out of 27 patients without trigger at aortic encroached site of LA and 1 (20%) out of 5 patients with trigger at aortic encroached site of LA had recurrence of AF. Conclusion The aorta contributed to low voltages on its encroachment area over the anterior wall of LA. Non-pulmonary vein triggers originating from the aortic encroachment area were found in 15.62% of total patients. Careful evaluation of the anatomical relationship between LA and aorta is important during AF ablation for a better long term outcome.
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