Transcatheter aortic valve replacement in low risk patients: a review of PARTNER 3 and Evolut low risk trials
Transcatheter aortic valve replacement (TAVR) has become a mainstay in treatment for patients with severe aortic stenosis who are considered high-risk surgical candidates. The use of TAVR in low-risk patients with severe aortic stenosis is being explored as an alternative to surgical aortic valve replacement (SAVR). Recent results from the Medtronic Evolut Low Risk trial and the Placement of Aortic Transcatheter Valves (PARTNER) 3 trial shed light on the use of TAVR in low-risk surgical candidates. The Evolut Low Risk trial compared TAVR with a self-expanding supra-annular bioprosthesis to SAVR in 1468 patients with severe aortic stenosis who were low surgical risk. Patients with a mean age of 74 and a mean Society of Thoracic Surgeons (STS) risk score of 1.9% were randomized to either TAVR or SAVR groups. Using the composite end point of death or disabling stroke at 24 months, the study found an incidence of 5.3% in the TAVR arm and 6.7% in the surgical arm. The Evolut Low Risk trial thus concluded that TAVR was statistically noninferior but not superior to SAVR (difference, −1.4 percentage points; 95% Bayesian credible interval for the difference, −4.9 to 2.1; posterior probability of noninferiority, >0.999). The PARTNER 3 trial assigned 1,000 patients with severe aortic stenosis and low surgical risk to either TAVR with transfemoral placement of balloon expandable valve or SAVR. Patients with a mean age of 73 and a mean STS score of 1.9% were randomized to either TAVR or SAVR groups. With respect to the primary endpoint of composite death from any cause, stroke, or rehospitalization, the study found an occurrence of 8.5% in TAVR and 15.1% in SAVR, confirming both noninferiority and superiority in the TAVR group [absolute difference, −6.6 percentage points; 95% confidence interval (CI), −10.8 to −2.5; P<0.001 for noninferiority; hazard ratio, 0.54; 95% CI, 0.37 to 0.79; P=0.001 for superiority]. Both the Evolut low risk trial and the PARTNER 3 trial provide evidence that the use of TAVR extends beyond the scope of high and intermediate risk surgical patients and is at the very least equivalent to SAVR in the treatment low-risk surgical candidates when using a transfemoral approach in patients without bicuspid aortic valves. In this article we provide an extensive review on the Evolute low risk and PARTNER 3 trials, including a discussion on clinically relevant outcomes.