Prior treatment does not influence the performance or early outcome of per-oral endoscopic myotomy for achalasia.
Jones EL, Meara MP, Pittman MR, Hazey JW, Perry KA. Prior treatment does not influence the performance or early outcome of per-oral endoscopic myotomy for achalasia. Surg Endosc. 2016 Apr; 30(4):1282-6.