Peroral endoscopic myotomy (POEM) was performed first in 2008 by Professor Inoue.
Its use is now widespread as a first-line treatment for achalasia, with similar efficacy
to Heller’s myotomy.
1
There are 2 main technical approaches to performing myotomy: anterior or posterior
submucosal tunneling. They have similar efficacy and safety, according to recent meta-analysis
and randomized controlled trial, although posterior POEM seems to be faster to perform2,
3, 4 and is preferable after Heller’s myotomy.
According to anatomic studies,
5
it is believed anterior POEM at the 2 o’clock position results in myotomy of the “clasp”
muscular fibers seen endoscopically as the continuation of the inner esophageal circular
muscle fibers, whereas posterior POEM at the 5 or 6 o’clock position results in myotomy
of the “clasp” fibers with risk of damaging the inner gastric oblique “sling” fibers
(Figs. 1 and 2).
Figure 1
Modified posterior peroral endoscopic myotomy direction according to two penetrating
vessels and the sling fibers.
Figure 2
Inner oblique (sling) muscular fibers and circular (clasp) muscular fibers.
It is important to avoid a long myotomy (>3 cm) because this might be associated with
higher post-POEM gastroesophageal reflux disease (GERD)
6
; it is also important to preserve the sling fibers because they may help to prevent
GERD by maintaining the acuity of the angle of His.
Recently, Tanaka et al
7
,
8
described the presence of two penetrating vessels (TPVs) as a good landmark to end
the submucosal tunnel and guide the myotomy direction to spare the sling fibers during
posterior POEM, with the potential of reducing the incidence of post-POEM GERD (Figs. 3
and 4).
Figure 3
Two penetrating vessels.
Figure 4
Posterior myotomy direction according to two penetrating vessels.
We aimed to study and characterize the presence of the TPVs according to sling fibers
in a prospective Western cohort of patients undergoing posterior POEM. We show the
endoscopic and technical details in Video 1 (available online at www.VideoGIE.org).
Methods
Patients
We included all consecutive cases of patients with achalasia who underwent posterior
POEM from November 2018 to February 2020 at 2 institutions. Written informed consent
was obtained from each patient before the study.
POEM procedure
Posterior POEM was performed by 1 endoscopist actively looking for the TPVs as described
by Tanaka et al,
7
using a standard gastroscope, short transparent cap, Hybrid Knife T-Type (Erbe, Tübingen,
Germany), CO2 insufflation, and coagulation grasper when needed.
The procedures were performed with the patient under general anesthesia and lying
in the supine position. A longitudinal mucosal incision and submucosal tunneling were
performed at the 5 to 6 o’clock position until reaching the gastroesophageal junction
(GEJ). The GEJ was defined by a narrowing area followed by expansion of the submucosal
space, the distance from the incisors (similar to the GEJ on the luminal side), the
presence of spindle veins, and edema at the level of the luminal side of the GEJ.
In doubtful cases, transillumination using a parallel slim endoscope or X-ray was
used to confirm the GEJ’s position.
After the GEJ, we modified the direction of the tunnel by looking actively for the
TPVs, trying to preserve the sling fibers, as described by Tanaka et al.
8
Careful dissection was needed at this point. If the penetrating vessels were not detected,
the tunneling and subsequent myotomy at the gastric level were carried out at around
the 3 to 4 o’clock position (toward the lesser curvature).
Selective esophageal myotomy was followed by a 2- to 3-cm gastric myotomy. After the
myotomy, the mucosal incision was closed with clips.
Outcomes
Clinical, anatomic, and technical endoscopic data were collected prospectively from
all cases. The distance from the incisors and clock position of the first and second
penetrating vessel were collected.
TPVs were defined as branches from the left gastric artery found in the posterior
wall of the gastric cardia, with the first vessel found immediately after passing
the GEJ and the second a few centimeters distally, as described by Tanaka et al.
7
,
8
Results
Twenty-three posterior POEM procedures were performed. The patient group was 52% male
and 48% female, with a mean age of 57 years (range, 24-80). Technical and clinical
success rates were 100% (minimum 30-day follow-up).
Cases included 6 sigmoid esophagus, 4 with previous Heller myotomy, 7 with previous
balloon dilation, and 6 cases of type 3 achalasia. Mean procedural time was 68 minutes
(range, 40-112). TPVs were identified in 16 cases (69.57%). The first vessel was usually
found immediately after or 1 cm distal to the narrow GEJ, at the 6 o’clock position,
and the second vessel usually was 1.5 to 2 cm distal (to the first vessel), at the
5 or 4 o’clock position (Table 1). Sling fibers were seen as internal oblique fibers
running at the left side of the TPVs. Only the first penetrating vessel was identified
in 4 cases (17.39%). The sling fibers were identified in 6 cases (26.08%). TPVs or
sling fibers were detected in 18 cases (78.26%) and at least 1 penetrating vessel
or sling fibers in 21 cases (91.30%).
Table 1
Location of two penetrating vessels
Characteristics
Value
Mean height (range), cm
165 (151-185)
First penetrating vessel
Mean distance from incisors (range), cm
42.5 (40-48)
Clock position (%)
6 (100)
Second penetrating vessel
Mean distance from incisors (range), cm
44.3 (42-49)
Clock position (%)
4 (50)5 (50)
Mean distance between penetrating vessels (95% confidence interval), cm
1.8 (1.5-2.1)
All patients completed at least 3 months of follow-up (range, 3-16 months), with a
clinical symptom evaluation. All patients started proton pump inhibition per protocol
after the POEM procedure. Use was discontinued after clinical evaluation in all asymptomatic
patients.
Regarding GERD symptoms, most patients remained asymptomatic (82%), and 4 patients
presented at least mild GERD symptoms. Upper endoscopy was performed in 4 patients:
2 were negative, 1 patient presented Grade A esophagitis, and 1 patient presented
Grade C esophagitis. In the latter case, TPVs were not identified during POEM.
Conclusions
TPVs seem to be easy to identify in a Western population. They seem to be a good indicator
of the optimal distal extent of posterior POEM and to guide myotomy to preserve gastric
oblique fibers (sling fibers), potentially reducing the incidence of post-POEM reflux.
When TPVs or sling fibers are not identified, the tunneling and subsequent myotomy
at the gastric level at the 3 to 4 o’clock position (toward the lesser curvature)
might be equivalent.