Background: There has been recent enthusiasm regarding the potential for endoscopic augmentation of the lower esophageal sphincter (LES). Hypotheses: Endoscopically-delivered expandable prostheses can be reliably and durably placed at the LES; plus, they can be titrated in number and easily removed.
Methods: Farm pigs (n=18) or Sinclair mini-swine (n=15) were studied for short-term or chronic studies, respectively. All animals had esophagogastroscopy under a general anesthetic for the placement of up to 13 hydrogel prostheses. The expanding prostheses were placed into the submucosal plane at the LES using an overtube-trocar delivery system. Surveillance endoscopy followed at intervals of 7 and 14 days (short-term) or up to 168 days (chronic). Pronounced intraluminal mucosal projection and/or fluoroscopy were used as in-vivo confirmation of successful delivery and retention. Histopathology was performed on all sacrificed animals (n=19.) Twelve prostheses were removed from 4 animals at 7, 14, or 168 days, using directed monopolar cautery and suction.
Results: Successful delivery of prostheses occurred in 99% of attempts (160/162.) Upon sacrifice, or at six months surveillance endoscopy, 84% of delivered prostheses remained undisturbed at the LES. Most "lost" prostheses passed uneventfully through the digestive tract within the first week- only one prosthesis was lost after 8 weeks of surveillance. No animal experienced a significant infection, although it is speculated that early loss of prosthesis may be due to bacterial contamination and ejection. There was no observable difficulty in delivering up to 13 prostheses throughout the region of the LES. Prosthesis extraction was considered simple, with complexity comparable to the endoscopic banding of non-bleeding varices. Histopathology specimens demonstrated well-encapsulated hydrogel prostheses surrounded by chronic and stable-appearing fibrotic reactions. No pathologic evidence of infection was demonstrated. Muscular wall thickness of the esophagus was unaffected at the regions of hydrogel prosthesis.
Conclusions: The endoscopic delivery of submucosal hydrogel prostheses in swine is safe and durable. Luminal projection occurs without damage to the underlying esophagus. Multiple prostheses can be readily placed, and these prostheses can be readily removed. Human safety and functional studies are underway.