S422 Associations Between Endosonographic Characteristics of Lower Esophageal Sphincter and Post-Myotomy Response in Achalasia Patients

Introduction: Peroral endoscopic myotomy (POEM) has become the forefront of achalasia treatment. It is unclear whether anatomical parameters of lower esophageal sphincter (LES) play any predictive role for selecting myotomy orientation or in determining clinical response. We aim to study the prognostic values of LES anatomical evaluation by endoscopic ultrasound (EUS) in achalasia patients. Methods: We retrospectively reviewed medical records and EUS findings of achalasia patients treated with POEM during 2019-2020. Baseline thickness of anterior and posterior muscular layers of LES were measured. Difference of ≤0.6mm between anterior and posterior wall was considered symmetrical LES. Eckardt score were recorded at 1, 3, and 6-month post-POEM. Clinical response was defined as a score of ≤3. High-resolution esophageal manometry and time barium esophagogram (TBE) were performed at baseline and 1-month. Results: Consecutive 22 patients (14 F, age 48±19, achalasia type 1:2:3=6:13:3) were included as described in Table. EUS revealed asymmetrically thickened LES in 50% of patients (n=11; 7 with anterior thicker than posterior side) (Figure 1). Among endosonographic parameters, thickness of muscular layers of anterior LES significantly correlated with pre-POEM manometric findings and TBE (Table). All patients underwent POEM (all with full thickness myotomy; 14 were posterior approach). Among patients with asymmetrical LES (n=11), there was no statistically significant difference of clinical response between myotomy at the thickened side (n=4) versus the contralateral (non-thickened) side (P=0.226). All patients who reached the 6-month endpoint (n=16) had good clinical response with 50% had complete resolution of symptoms; Eckardt score=0. LES pressure and integrated relaxation pressure (IRP) significantly improved at 1-month (P=0.023 and P=0.001, respectively) with LES pressure ≤15 mmHg in 94% and normalized IRP in 75%. TBE at 1-month post POEM (n=13) revealed >50% reduction in barium height on 5-minute film in 70% of the patients. Conclusion: Anatomical variation of LES is common in achalasia patients. Although the thickness of the anterior LES was associated with higher LES pressure, integrated relaxation pressure, and barium height, myotomy can be performed at any orientation. A hundred percent clinical response of POEM regardless of myotomy approach reiterates the efficacy of this therapeutic modality in patients with achalasia.Figure 1.: Endosonographic appearances of (A) symmetrically non-thickened LES and (B) Asymmetrically thickened muscularis mucosae and muscularis propria of the anterior wall of LES (yellow arrow)Table 1.: Demographic Data, Endosonographic Findings And Correlation With Pre-POEM Physiologic Study; BMI: Body mass index, LESP: lower esophageal sphincter pressure, IRP: Integrated relaxation pressure, TBE Height: Barium height on 5-minute film of Time barium esophagogram, MM: Muscularis mucosae, MP: Muscularis propria, *p<0.05