Low Risk Transcatheter Aortic Valve Replacement: Taking the Plunge and Embracing a Paradigm Shift

The landscape of managing patients with severe aortic stenosis (AS) has remarkably changed with the development of transcatheter aortic valve replacement (TAVR).TAVR was initially validated in inoperable patients with severe AS demonstrating superiority in comparison with use of medical therapy [1,2].Technological advances and procedural simplification led to expansion to those at high surgical risk and subsequently intermediate surgical risk [3][4][5][6].Societal guidelines have supported the use of TAVR as standard of care in these patients (Table 1) [7,8].Most recently, TAVR was studied in severe AS patients with low surgical risk using both the self-expanding supra-annular bioprosthesis (CoreValve, Evolut R, Evolut PRO; Medtronic) [10] and the balloon-expandable valve (SAPIEN 3; Edwards Lifesciences Corp., CA, USA) [9] in comparison with those undergoing surgical aortic valve replacement (SAVR).Both studies were multicenter, randomized and noninferiority clinical trials.The Evolut Surgical Replacement and Transcatheter Aortic Valve Implantation in Low Risk Patients trial randomized 1468 patients with a mean age of 74 years and found an estimated incidence of the primary end point, defined as a composite of all-cause mortality or disabling stroke at 24 months, in 5.3% of patients undergoing TAVR versus 6.7% of patients undergoing SAVR (posterior probability of noninferiority >0.999) [10].In terms of safety, patients who underwent TAVR, as opposed to SAVR, had a lower incidence of disabling stroke, bleeding complications, acute kidney injury and atrial fibrillation and a higher incidence of moderate or severe aortic regurgitation and pacemaker implantation at 30 days.The placement of aortic transcatheter valves (PARTNER) 3 trial randomized 1,000 patients with a mean age of 73 years and found the incidence of the composite end point, defined as all-cause mortality, stroke, or rehospitalization, to be significantly lower at 12 months among patients who underwent TAVR in comparison to SAVR (8.5 vs 15.1%; p < 0.001 for noninferiority; p = 0.001 for superiority) [9].Moreover, those who underwent TAVR had a lower risk for new-onset atrial fibrillation, poor treatment outcome and shorter index hospitalization with no significant between-group differences in major vascular complications, new permanent pacemaker insertions, or moderate or severe paravalvular regurgitation compared with those who underwent SAVR.As a result of these trials, TAVR was approved for use in low risk patients with severe AS by both the Centers for Medicare and Medicaid and US FDA.In the background of these landmark studies, the number of TAVR procedures performed in the USA has now surpassed the number of isolated SAVR [11].With the addition of low risk severe AS patients to this pool, the volume of TAVR is expected to rapidly increase and likely surpass all aortic valve procedures of any type in 2020 [12].To put this into perspective, Thourani et al., described almost 80% of 141,905 SAVR patients between 2002 and 2010 to be of low surgical risk [13].In the future, a large proportion of these patients may instead undergo TAVR.Additionally, recent studies have suggested that the need for TAVR may significantly increase for reasons outside of expansion into territory of which SAVR was previously the gold standard, including an underdiagnosis of severe AS in the community, a rising burden of disease, and possible benefit in patients with moderate AS.D'Arcy et al., reported identification of new valvular heart disease in half of primary care participants aged ≥65 years old when