A) Esophageal Complications
The proximity of the esophagus to the posterior wall of the left atrium (LA) limits power delivery and hence the quality of lesion. There is no consensus on the best RF setting to create effective transmural lesions on the posterior wall while minimizing risk of esophageal thermal injury. Conventionally, the preferred ablation strategy over the posterior wall is a low power setting (ranging from 20-30 W). However, several studies have shown safety of HPSD technique with regards to esophageal complications. In a study utilizing late gadolinium enhancement magnetic resonance imaging (LGE MRI) to assess extent and persistence of esophageal thermal injury post AF ablation, moderate to severe esophageal enhancement was seen in 14.3% patients undergoing AF ablation with both HPSD (50 W/ 5 s) and LPLD (<35 W for 10 to 30 s) ablation strategies on same day LGE MRI.32 There were no atrioesophageal fistulas noted even with use of CF catheters in the HPSD group underlining the importance of appropriate titration of ablation parameters on the posterior wall (i.e., short duration of 5 s or less, and reduced CF on the posterior wall to 10 to 15 g).32 Posterior wall applications using 45-50 W for 2-10 s have been noted to be safe in a multicenter study by Winkle et al.31 In a study including 10,284 patients from 4 experienced centers, 1 atrioesophageal fistula (0.0087%) occurred in 11,436 HPSD ablations performed using 45–50 W for 2-10 s on the posterior wall, while 3 atrioesophageal fistulas (0.12%) occurred in 2,538 LPLD ablations using 35 W on the posterior wall for 20 s (p = 0.021). Notably, the researchers reported that 2 of the 3 atrioesophageal fistulas in the 35 W group did not undergo esophageal temperature monitoring. In another retrospective study including 76 AF patients, there was a trend towards less esophageal heating with HPSD technique (45 W for 6 s on the posterior wall with CF 8-15 g & 50 W for 6 s on the anterior wall with CF 10-20 g) compared to LPLD technique (30 W for 30 s with CF 10-30 g) with the incidence of esophageal heating being 51.2% in the HPSD group and 74.3% in the LPLD group (p = 0.0578).30