Evolut low-risk trial
The Evolut trial enrolled 1,414 patients with low surgical risk who were randomly assigned to TAVR, a self-expanding supra-annular CoreValve Evolut R PRO, or surgery.
By 4 years, the primary endpoint of all-cause mortality or disabling stroke had occurred in 10.7% of the TAVR group and 14.1% in the surgery group (hazard ratio, 0.74; P = .05), representing a 26% relative reduction with TAVR.
The absolute difference between treatment arms for the primary endpoint continued to increase over time: 1.8% at 1 year, 2.0% at 2 years, 2.9% at 3 years, and 3.4% at 4 years.
Rates of the primary endpoint components were all-cause mortality 9.0% with TAVR vs. 12.1% with surgery (P = .07); and disabling stroke was 2.9% with TAVR) vs. 3.8% for surgery (P = .32). Aortic valve rehospitalization was 10.3% with TAVR vs. 12.1% with surgery (P = .27).
The composite of all-cause mortality, disabling stroke, or aortic valve rehospitalization was significantly lower with TAVR, compared with surgery (18.0% vs. 22.4%; HR, 0.78; P = .04).
New permanent pacemaker implantation was significantly higher in the TAVR group (24.6% vs. 9.9%).
Indicators of valve performance including aortic valve reintervention (1.3% TAVR vs. 1.7% surgery); clinical or subclinical valve thrombosis (0.7% TAVR vs. 0.6% surgery); and valve endocarditis (0.9% TAVR vs. 2.2% surgery) were similarly low between groups, the authors report.
TAVR patients had sustained improvement in hemodynamics as measured by echocardiography, with significantly lower aortic valve mean gradients (9.8 mm Hg TAVR vs. 12.1 mm Hg surgery) and greater effective orifice area (2.1 cm2 TAVR vs. 2.0 cm2 surgery).
At 4 years, 84.7% of TAVR patients and 98.4% of surgery patients had no or trace paravalvular regurgitation, and there was no difference between groups in moderate or greater paravalvular regurgitation (0.4% TAVR vs. 0.0% surgery).
“The Evolut valve has shown a superior performance to surgery,” Dr. Reardon concluded. “It has less structural valve deterioration, less severe patient prosthetic mismatch, and superior hemodynamics, compared to surgery. All these factors are translating into a widening difference in clinical event curves year on year with the Evolut valve vs. surgery.”
Why the difference between trials?
The big question is why the early benefit seen with TAVR vs. surgery in both trials was attenuated by 5 years in PARTNER-3 but seemed to become greater each year in the Evolut trial. There were no definite explanations for these observations, but several possibilities were suggested.
Dr. Leon noted that with trials of intervention vs. surgery, it is common for the intervention group to do better in the beginning and for surgery to catch up a bit in later years. “So, it is not that much of a surprise to see outcomes plateauing in PARTNER-3.”
But he also suggested some other factors that may have played a role, one of which was the COVID pandemic.
“During the 2-year COVID period more than 75% of the deaths and strokes in the trial occurred in the TAVR patients,” he said. “Surgery patients were getting more anticoagulation because they had more paroxysmal [atrial fibrillation]. We know that COVID is a stimulus of thrombogenic events so in an odd way we think there may have been some cardioprotective effects from anticoagulation therapy in the surgery group.”
He also pointed out that though hospitalization and strokes were slightly lower with TAVR vs. surgery in the PARTNER-3 trial, mortality was slightly greater in the TAVR group.
“There was a 2:1 ratio in the TAVR and surgery groups in noncardiovascular deaths which influenced the all-cause mortality numbers,” he noted.