SNOWMASS, COLO. – There are now more transcatheter aortic valve replacements performed each year than surgical ones in the United States, a disparity that may grow vastly larger.
That’s if the results of the two pivotal randomized trials comparing transcatheter aortic valve replacement (TAVR) and surgical aortic valve replacement (SAVR) in low-surgical-risk patients scheduled for presentation at the annual scientific session of the American College of Cardiology in March turn out to show TAVR outcomes are equivalent or superior to SAVR.
And that just might be the scenario, provided the eye-popping results already reported from another, much smaller study – the Low Risk TAVR study, a 200-patient, prospective, nonrandomized, observational study – are at all reflective of what’s to come when the pivotal PARTNER 3 and EVOLUT R trials are released at the ACC meeting in New Orleans, Michael J. Mack, MD, said at the Annual Cardiovascular Conference at Snowmass sponsored by the American College of Cardiology.
“The TAVR train has left the station on the way to low risk, and I don’t really see it coming back,” said Dr. Mack, medical director for cardiothoracic surgery at Baylor Scott & White Health in Dallas.
He wasn’t part of the Low Risk TAVR study, in which 200 low-surgical-risk patients with symptomatic severe aortic stenosis underwent TAVR with contemporary devices at 11 centers and were matched to 719 historical control SAVR patients at the same centers. But he called the study results “pretty spectacular”: zero 30-day all cause mortality in the TAVR group versus 1.7% with SAVR, no in-hospital strokes with TAVR versus a 0.6% rate with SAVR, and similar permanent pacemaker implantation rates of 5.0% with TAVR and 4.5% with SAVR.
Also, the TAVR group had a mere 3.0% rate of new-onset atrial fibrillation, a 2-day hospital length of stay, and a 0.5% incidence of greater-than-mild paravalvular leak at 30 days (J Am Coll Cardiol. 2018 Oct 30;72:2095-105).
The two major trials due to report 1-year outcomes at the ACC meeting in March are similarly designed. The PARTNER 3 trial includes 1,000 low-surgical-risk patients with a mean age of 73 years and a predicted 30-day surgical mortality risk of 1.9%. Seventy-one percent of them were New York Heart Association (NYHA) Class II at enrollment. Participants were randomized to TAVR with the Edwards Lifesciences Sapien 3 valve or to SAVR, with the primary outcome being a composite of all-cause mortality, stroke, and rehospitalization 1 year post procedure. The EVOLUT R trial is similar, except the TAVR valve is the Medtronic CoreValve.
Both trials will continue to follow patients annually for 10 years in order to address the still-open issue of TAVR and SAVR valve durability. Also, the Food and Drug Administration has mandated that 4D CT imaging substudies be conducted in 800 of the combined 2,000 participants in the two trials in order to provide new insight into the issue of subclinical valve leaflet thrombosis, which was detected in 14% of participants in the Low Risk TAVR study 30 days post procedure.
“The clinical impact and need for anticoagulant therapy are currently unknown. However, clot anywhere else in the body doesn’t do good things, so it’s hard to imagine it’s helping here. Pretending it doesn’t exist isn’t going to make the problem go away,” Dr. Mack said.
The 4D CT imaging substudy results are expected to be presented later this year at the Transcatheter Cardiovascular Therapeutics conference in San Francisco.
In 2017, 51,064 TAVR procedures for symptomatic severe aortic stenosis were done in the United States, compared with 41,490 SAVRs. The past several years have seen a decreasing proportion of TAVRs being done in high-surgical-risk patients and a growing proportion in intermediate-risk patients.
Even if PARTNER 3 and EVOLUT R prove to be resoundingly positive for TAVR in low-risk patients, however, SAVR is not going to vanish, according to Dr. Mack. He cited four factors working against universal adoption of TAVR: the uncertainty surrounding valve durability, which will take years to resolve; the issue of TAVR valve leaflet thrombosis and the for-now theoretic possibility that all TAVR patients might need to receive postprocedure oral anticoagulation; the high rate of new permanent pacemaker implantation associated with TAVR, which Dr. Mack called the procedure’s Achilles heel; and the total absence of high-quality data on TAVR in patients with bicuspid aortic stenosis.
Even though TAVR for diseased bicuspid valves is not off-label therapy – the FDA’s indication for TAVR is for native valve aortic stenosis – patients with bicuspid valves weren’t included in any of the randomized trials, he explained.
Younger patients are likely to stick with SAVR for the foreseeable future, regardless of the outcomes of PARTNER 3 and EVOLUT R, according to the surgeon, because of the unresolved issue of valve durability, as well as TAVR’s greater associated need for a permanent pacemaker, both significant considerations in individuals with a life expectancy of another 20-30 years.
There are now roughly 600 TAVR centers and 1,150 SAVR centers nationally. One of the hot topics in the field stems from the fact that half of these TAVR centers do only one TAVR per week or less. That’s concerning in light of a recent New York State study showing a clear association between operator volume and outcomes.
“The more you do, the better your outcomes are, similar to many other procedures in medicine,” Dr. Mack commented.
On the other hand, it’s unlikely that patients who present to one of the roughly 550 SAVR-only centers are truly getting informed consent as to their options, he added.