Current Key Issues in Transcatheter Aortic Valve Replacement Undergoing a Paradigm Shift

TAVR with supporting evidence. Current Treatment Strategy Guided bySurgical Risk Score TAVR vs. SAVR or Standard Therapy According to Risk Scores Early in the introduction of TAVR, its clinical role was demonstrated among inoperable patients with severe AS (Society of Thoracic Surgeons [STS] score >15%) and those with high surgical risk (STS score, 10-15%) (Table 1).2-5 Among intermediate-risk patients (STS score, 4-10%) with severe AS, large trials reported that TAVR resulted in similar, or even better, outcomes in terms of the risks of death and disabling stroke, hemodynamic parameters, hospital stay, and quality of life, compared with SAVR (Table 1).6-8 These findings indicate that TAVR was a reasonable alternative to SAVR for intermediate-risk patients with severe AS. 2Subsequently, the attentions at the front line of clinical practice turned to low-risk patients, and several studies showed acceptable outcomes in the low-risk patients that render optimistic expectations (Table 1).9-11 Although the outcomes of TAVR in low-risk patients had been questioned, the Evolut Low Risk trial showed that TAVR with Evolut-R was non-inferior to SAVR in terms of a composite of death or disabling stroke at 24 months among more than 1,400 patients with an average STS score of 1.9%.12 N ew technologies, according to the Gartner hype cycle theory, have 5 phases from conceptual presentation to generalized adoption.1 The introduction and distribution of transcatheter aortic valve replacement (TAVR), or transcatheter aortic valve implantation (TAVI), demonstrated similar patterns (Figure 1), but since its emergence, TAVR has been attracting much attention as an alternative to surgical aortic valve replacement (SAVR).Given the potential benefits of this noninvasive procedure and the unmet clinical need in real-world practice, clinicians and researchers imposed huge expectations and enthusiasm on TAVR ("peak of inflated expectations"), which was then criticized for the risk of complications and uncertainties about device durability and long-term prognosis ("trough of disillusionment").These concerns were then rebutted with numerous studies from clinical trials and registries that reported favorable outcomes of TAVR, compared with SAVR ("slope of enlightenment"), and it is expected that ongoing trials with constructive discussion will clarify the optimal treatment strategy for applying TAVR in various AV diseases ("plateau of productivity").Currently, there are active debates regarding the clinical role, long-term durability, risk of complications, and expanding indications of TAVR in patients with low surgical risk, bicuspid AV, moderate aortic stenosis (AS) with heart failure (HF), and bioprosthetic valve failure.In this article, we summarize the current issues in TAVR, and review the expectations for expanding the clinical indications of