This paper presents a method for assisting the placement of stented aortic valve prosthesis during minimally invasive off-pump transcatheter aortic valve implantation (TAVI) under live 2-D X-ray fluoroscopy guidance. The proposed method includes a dynamic overlay of an intra-operative 3-D aortic root mesh model and an estimated target area of valve implantation onto live 2-D fluoroscopic images. This is based on a template-based tracking procedure of a pigtail catheter without further injections of contrast agent. Minimal user-interaction is required to initialize the algorithm and to correct fluoroscopy overlay errors if needed. Retrospective experiments were carried out on ten patient datasets from the clinical routine of the TAVI. The mean displacement errors of the updated aortic root mesh model overlays are less than 2.0 mm without manual overlay corrections. The results show that the guidance performance of live 2-D fluoroscopy is potentially improved when using our proposed method for the TAVIs.