Background Esophageal myotomy using submucosal endoscopy with mucosal safety flap (SEMF) has been proposed as a new treatment of achalasia. In this technique, a partial-thickness myotomy (PTM) preserving the longitudinal outer esophageal muscular layer is advocated, which is different from the usual full-thickness myotomy (FTM) performed surgically. The aim of this study was to compare endoscopic FTM and PTM and analyze the outcomes of each method after a 4 week survival period. Methods Twenty-four pigs were randomly assigned into group A (FTM, 12 animals) and group B (PTM) to undergo endoscopic myotomy. Lower esophageal sphincter (LES) pressure was assessed using pull-through manometry. For statistical analysis we compared the average esophageal sphincter pressure values at baseline, after 2 weeks, and after 4 weeks between groups A and B. The P value was set as <0.05 for significance. Results Eighteen animals were included for statistical analysis. Mean (SD) LES pressures were similar between groups A and B (nine animals each) at baseline [group A = 23 (10.4) mmHg; group B = 20.7 (8.7) mmHg; P = 0.79], after 2 weeks [group A = 19 (7.7) mmHg; group B = 21.8 (8.4) mmHg; P = 0.79], and after 4 weeks [group A = 22.6 (10.2) mmHg; group B = 20.7 (9) mmHg; P = 0.82]. LES pressures were significantly reduced in three animals after 4 weeks: one animal (1%) in group A and two animals (2.5%) in group B. An extended myotomy (3 cm below the cardia) was achieved in three animals and was responsible for the significant drop in LES pressure seen in the two animals from group B. Conclusion Esophageal myotomy using SEMF is a feasible yet challenging procedure in pigs. Full-thickness myotomy does not seem to be superior to partial-thickness myotomy as demonstrated by pull-through manometry. Endoscopic esophageal myotomy results are greatly influenced by obtaining adequate myotomy extension into the gastric cardia.
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