Per-oral endoscopic myotomy (POEM) is a minimally invasive therapy for achalasia. The procedure has demonstrated high technical and clinical success with lower adverse events. Different types of knives have been used for cutting and coagulation during the procedure; however, exchanging accessories is sometimes needed to perform all the stages of POEM. To overcome this disadvantage, the investigators aim to evaluate a single device that integrates in its tip bipolar radiofrequency and microwave, the Speedboat Ultraslim (Creo Medical, UK) for cutting and coagulation during POEM procedure. Some of the promise's advantages derived from its use are: (1) less inflammation, (2) clear differentiation between layers, (3) the use of a single device for the procedure. This single-center, prospective, interventional study will include patients with achalasia submitted to POEM procedure, with or without fundoplication (POEM-F). All stages (mucosal incision, submucosal tunneling, myotomy) of POEM will be performed using the Speedboat ultraslim flexible catheter. Technical and clinical success, along with safety will be the primary endpoints; while, post-procedure reflux symptoms and quality of life will be assessed as secondary outcomes with reflux severity index (RSI) and the Northwestern Esophageal Quality of Life (NEQOL), respectively.