Historical notes: The road to peroral endoscopic myotomy

Submucosal endoscopy with saftey valve mucosal flap was developed in the animal laboratory of the Mayo Clinic Developmental Endoscopy Unit. This concept, and ultimately clinical technique, was an outgrowth of earlier efforts to improve endoscopic excision of mucosal disease by manipulating the submucosa. The ability of the mucosa to readily separate from the submucosa (delaminate) was the critical observation that was refined into a method transforming the submucosa into a working space while allowing the overlying mucosal flap to serve as a protective barrier.