1 Transcatheter aortic valve implantation in symptomatic severe aortic stenosis: where do we stand?rnAortic stenosis occurs in 2％-9％ of patients over the age of 65, the most common cause being degenerative[1,2] The preferred treatment in symptomatic severe aortic stenosis(SAS) is surgical aortic valve replacement (SAVR), but in the elderly, the surgical risk can be greater than the benefit.[3]Since Alain Criblier performed the first percutaneous tran?scatheter aortic valve implantation (TAVI) in 2004, many studies have demonstrated that this technique is non-inferior to SAVR and superior to medical therapy in inoperable pa?tients with symptomatic SAS.[4] TAVI is a great progress in the management of SAS because it is safer than SAVR in the elderly, in whom symptomatic SAS is very frequent.According to the current guidelines, this is a class I recom?mendation of treatment in patients with symptomatic SAS who are not suitable for SAVR, as assessed by the Heart Team.[3,5] At the same time, there are some situations in which TAVI is difficult to perform: any unfavorable vascu?lar access to the aorta, size of the aortic annulus out of range for TAVI, short distance between the coronary ostia and aortic valve annulus, degree and pattern of calcification unfavorable to TAVI, bicuspid aortic valve, aortic or left ventricular thrombosis, suspicion of aortic valve endocardi?tis, aneurysm of the ascending aorta, concomitant severe mitral valve and severe tricuspid valve disease, and coro?nary artery disease requiring coronary revascularization by coronary artery by-pass grafting. In these situations, the in?dication is to perform SAVR, but in most cases, the surgical risk is very high.