Achalasia is a relatively rare esophageal motility disorder resulting from a nonrelaxing lower esophageal sphincter (LES) and loss of normal peristalsis. The primary symptoms — dysphagia and regurgitation — can lead to chronic inflammation and potentially to dysplasia and carcinoma.
Heller myotomy has long been considered the most durable and effective therapy for achalasia. Now performed laparoscopically, it has become less invasive, although access to the esophagus for that component of the myotomy requires extensive dissection.
More recently, peroral endoscopic myotomy (POEM) has emerged as an endoscopic alternative to surgical myotomy. Early studies have shown that POEM is at least as safe and effective as surgery, with shorter procedure and recovery times and fewer serious complications.
"It was a technique from the animal lab that matured into a clinical method," says Christopher J. Gostout, M.D., of Mayo Clinic in Rochester, Minn. "With the development of natural orifice transluminal endoscopic surgery (NOTES) in 2004, a great deal of research in animal laboratories was focused on developing endoscopic versions of laparoscopic procedures."
In fact, submucosal endoscopy with mucosal safety flap is the result of work that began a decade ago in the animal laboratory of Mayo's Developmental Endoscopy Unit. The aim was to use the submucosa as a work space for endoscopic interventions with the overlying mucosa serving as a protective conduit. The technique allowed safer off-set entry into the mediastinum and peritoneal cavity, making therapeutic endoscopy procedures like POEM possible.
In 2008 in Japan, Haruhiro Inoue, M.D., used the submucosal tunnel approach to perform the first human endoscopic myotomy for achalasia. His technique — injecting saline into the submucosal space, creating a mucosotomy, developing a tunnel along the right wall of the esophagus extending about 4 centimeters into the stomach, then meticulously dissecting the circular muscle layer and closing the mucosotomy site with clips — is still the one most commonly performed today, though Western endoscopists often perform blunt tunnel dissection with a small, soft balloon instead of the dedicated endoscopic submucosal dissection (ESD) knife used in Asia.
Dr. Gostout notes that aside from the lack of external incisions and resulting trauma, a chief advantage of endoscopic myotomy is that dissection occurs from the inside out. "Cutting from the outside in is more dangerous because if the lining of the stomach or esophagus is perforated, the result is infection and possibly fistula," he says. "In POEM, the mucosal lining remains intact and the overlying mucosa serves as a protective flap and bandage."
POEM remains an evolving technique. Dr. Inoue and others continue to perform a partial-thickness myotomy — dissecting only the circular muscle layer and preserving the outer longitudinal esophageal muscles. But Mayo Clinic and a few other centers now perform a modified POEM that duplicates surgical full-thickness myotomy with Dor fundoplication.
Dr. Gostout says this hybrid procedure — a collaboration between endoscopists and thoracic surgeons — offers patients and physicians the best of both worlds. "For thoracic surgeons, the easiest part of Heller myotomy is cutting the muscles on the surface of the stomach; the most difficult is dissecting up into the chest cavity. So in the hybrid POEM, the endoscopist extends the procedure as far into the stomach as possible and if it looks satisfactory — there is currently debate about how much of the gastric side should be cut — then the surgeon performs the anti-reflux procedure."
Patients benefit from a significant reduction in the risk of reflux — a frequent complication of myotomy resulting from disruption of the LES and phrenoesophageal attachments. "Everybody is recognizing the heartburn problem," Dr. Gostout says. "We have good PPIs, but to be dependent on them for the rest of your life is just trading one problem for another."
Although few serious procedure-related adverse events have been reported, potential complications include branch bleeding off the left gastric artery and inadvertent coagulation injury to the mucosal flap during ESD of the tunnel, with accompanying risk of fistula and abscess. "We're dutiful about watching the mucosa, and if there appears to be an inadvertent injury we immediately seal the area with mucosal clips," Dr. Gostout says.
The universally reported greater than 90 percent success rate of POEM is similar to that of laparoscopic Heller myotomy, but interventional endoscopic expertise is essential for successful outcomes, even with less-complex circular muscle myotomy.
Dr. Gostout notes, "It's not for everyone, digging into the wall of the esophagus, staring at the muscle layer and wondering where to go if you make a mistake."
Bonin EA, et al. A comparative study of endoscopic full-thickness and partial-thickness myotomy using submucosal endoscopy with mucosal safety flap (SEMF) technique. Surgical Endoscopy. 2012;26:1751.
Li QL, et al. Peroral endoscopic myotomy for the treatment of Achalasia: A clinical comparative study of endoscopic full-thickness and circular muscle myotomy. Journal of the American College of Surgeons. In press.