Background: Peroral endoscopic myotomy (POEM) is a standard treatment option in achalasia. The endoluminal functional lumen imaging probe (FLIP) system utilizes impedance planimetry to measure diameter and distensibility at the esophagogastric junction (EGJ) in real-time. Most reports of the intraoperative FLIP experience focus on the 8 cm balloon. The 16 cm balloon catheter also provides topographical assessments in addition to EGJ metrics. The aim of this study is to characterize the findings and utility of the 16 cm balloon during POEM.
Methods: We conducted a retrospective review of consecutive patients who underwent POEM with intraoperative FLIP with the 16 cm balloon between January 2020 to September 2023. Operative reports were collected, analyzed, and data including myotomy length and EGJ metrics were recorded. Diameter and distensibility index pre and post myotomy were compared at 60 mL volume. Topographical assessments were used to guide the length of myotomy. Post myotomy FLIP measurements were used to gauge adequacy of myotomy. Follow-up occurred between 3-6 months and FLIP metrics from postoperative endoscopies were assessed and recorded when available.
Results: In total, 100 patients (57 females, mean age 56.1 years) who underwent POEM with intraoperative FLIP with the 16 cm catheter were enrolled. Preoperative diagnoses included the following: Achalasia (82 patients, with 11 type I, 49 type II, 22 type III), Esophagogastric outflow obstruction (15 patients), and hypercontractile esophagus (3 patients). 3 patients had an epiphrenic diverticulum. 37 patients had prior interventions (11 pneumatic dilation, 11 large caliber hydraulic balloon dilation, 15 botulinum injection to GEJ (approximately 1 year prior), and 13 prior myotomy). Spastic reactive contractile response patterns were noted in the body in 25 cases. Spastic activity above the myotomy was noted in 10 cases with previous myotomy and above the epiphrenic diverticulum in 2 cases. The median EGJ-diameter and EGJ-distensibility were 7.2 mm (IQR: 3.7) and 0.9mm²/mmHg (IQR: 1.2) pre-myotomy and 12.0 mm (IQR: 2.2) and 3.2 mm²/mmHg post myotomy (IQR: 1.6) (Figure 1). The mean myotomy length was 8.2 cm (range 3-15 cm) with 10 cases receiving a myotomy of 4 cm or less, guided by FLIP. 74 (74.0%) cases had a documented post myotomy EGJ-distensibility >2.0 mm²/mmHg. Additional myotomy after the post myotomy FLIP was performed in 20 cases to either extend the myotomy based on panometry or to increase the distensibility. The 3-6 month post POEM mean EGJ-diameter and EGJ-distensibility were 13.2 mm and 5.3 mm²/mmHg, respectively.
Conclusions: Intraoperative FLIP assessments using a 16 cm balloon may allow a tailored myotomy length and ability to gauge adequacy of myotomy. This may be particularly useful in cases of prior intervention, abnormal anatomy, or spastic activity.

Figure 1. The distributional characteristics of (a) EGJ-diameter and (b) EGJ-distensibility index are displayed at a balloon distension volume of 60 mL.

Ashton Ellison

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