Abstract
Background
Peroral esophageal myotomy (POEM) is an endoscopic surgical operation for achalasia. Here, we analyze a single-series POEM learning curve and examine which preoperative patient factors are predictive of operative difficulty.
Methods
Two surgeons performed all POEM procedures conjointly. Nonlinear regression was used to determine the learning curve for procedure time. Preoperative patient characteristics were correlated with outcomes.
Results
Thirty-six POEM procedures were performed. Total operative time did not decrease over the course of the series (mean 112 ± 36 min). Time required to complete the procedural steps of submucosal access and myotomy did decrease with experience, both exhibiting a “learning rate” of seven cases. The incidence of inadvertent mucosal perforations and the number of clips required both decreased with experience. Postoperative Eckardt scores at 1-year follow-up decreased over the course of the series. Prior endoscopic treatment, symptom duration, and esophageal width were all independently predictive of longer procedure time. Preoperative symptom duration was also positively associated with inadvertent mucosal perforation and the number of clips required.
Conclusions
In this series, overall procedure time did not decrease with experience and may not be an important marker of procedural skill for POEM. Prior endoscopic treatment, longer symptom duration, and esophageal dilatation may result in increased operative difficulty during POEM.
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Acknowledgments
The authors would like to acknowledge Remedios Manuel, RN; Rowena Martinez, RN; and Colleen Krantz, RN for their help in coordinating the clinical aspects of this study.
Conflict of Interest
Olympus America, Inc. granted instruments used during the POEM procedures, but was not involved in the design, data collection, analysis, or manuscript preparation for this study. Nathaniel Soper is on the scientific advisory boards of TransEnterix and Miret Surgical, both of which are unrelated to this study. Ezra Teitelbaum, Fahd Arafat, Byron Santos, Peter Kahrilas, John Pandolfino, and Eric Hungness have no conflicts of interest or financial ties to disclose.
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Discussant
Dr. Giovanni Zaninotto (Padova, Italy): First of all, I would like to congratulate you and your coworkers for this excellent, detailed, and in-depth analysis of the learning curve for POEM and the patient factors that may influence it. POEM is an innovative procedure but is becoming widespread: it will stay side by side with the old, time-honored endoscopic and surgical procedures for achalasia, and we need to learn how to include it in our armamentarium. That is why I think your presentation will have a marked impact on the medical community and also why I have a few questions to ask.
You have clearly shown that the overall time taken to perform POEM does not become shorter, the more procedures an operator performs, and you said that the operating time alone may not be representative of a greater mastery of the operation. I have noted in the literature that the mean time reportedly taken by Japanese and Chinese authors is about 30–40 min shorter than yours.
All the Far Eastern authors had an operative endoscopic background, with a great deal of experience of operative endoscopy and mucosectomy: could it be that operators with a surgical background take longer to complete the procedure and/or have a longer learning curve?
My second question concerns the patient factors that influence the time it takes to perform POEM: can you tell us more about which steps in the procedure are most affected by these factors? I would expect previous endoscopic therapies to make the myotomy step more difficult and therefore longer, whereas a larger esophageal diameter may have more of an effect on the fashioning of the submucosal tunnel. Could you comment on that?
A third question is regarding the type of previous endoscopic therapy: did you find any difference between previous pneumatic dilations and previous Botox injections?
Finally, although this last question goes beyond the aim of your presentation, could you tell us anything about the outcome of POEM in type three achalasia patients? Do you achieve the same results as in types two and one? Will POEM be the optimal treatment for these difficult patients?
I would like to thank the Society for giving me the privilege of discussing this interesting presentation and the authors for allowing me to read their manuscript well in advance.
Closing Discussant
Dr. Ezra Teitelbaum: Dr. Zaninotto, thank you for your insightful questions. We use a technique, similar to the one developed by Dr. Haru Inoue, which utilizes an anterior myotomy. The practitioners of this technique with the most clinical experience, Dr. Inoue and Dr. Lee Swanstrom who are both surgeons, have reported operative times similar to ours, at approximately 2 h. Ren and colleagues reported a shorter mean operative time of 66 min in their series using a posterior myotomy technique but also experienced higher rates of pneumothorax and subcutaneous emphysema. It is unclear whether the differences in operative times between these series are due to technique or clinician background, but I think it should be emphasized that regardless of specialty and experience, any physician will need to develop new skills before performing POEM. For this reason, extensive preclinical laboratory training is required and we would recommend being proctored initially by an experienced practitioner.
To answer your second question, interestingly we have found that both prior endoscopic treatment and prolonged symptom duration have the biggest impact on the submucosal tunnel dissection, rather than the myotomy. Both seem to cause a thickening and scarring of the submucosa that is especially pronounced at the esophagogastric junction, making tunnel dissection more difficult and potentially increasing the likelihood of inadvertent mucosal perforation. Increased esophageal width, on the other hand, appears to make clip closure of the mucosotomy more difficult.
So far, our experience with patients who have undergone prior endoscopic therapy is limited to four patients. Two had prior Botox injections, one had multiple pneumatic dilations, and one had been treated with both modalities, so while it seems that both therapies cause scarring of the submucosa, it is too early for us to discern which is worse.
In response to your last question regarding achalasia subtype, we have performed POEM on six patients with type III achalasia. So far, all have done extremely well in regards to both resolution of dysphagia and chest pain. Although the procedure is most anatomically analogous to a Heller myotomy, it remains to be seen which types of patients do best after POEM specifically. As you allude to, assessment of long-term outcomes will be especially critical in patients with type III achalasia, a subset that has relatively poor outcomes when treated with either Heller myotomy or pneumatic dilation.
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Teitelbaum, E.N., Soper, N.J., Arafat, F.O. et al. Analysis of a Learning Curve and Predictors of Intraoperative Difficulty for Peroral Esophageal Myotomy (POEM). J Gastrointest Surg 18, 92–99 (2014). https://doi.org/10.1007/s11605-013-2332-0
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DOI: https://doi.org/10.1007/s11605-013-2332-0