SNOWMASS, COLO. – The number of transcatheter aortic valve replacements (TAVRs) performed annually in the United States is forecast to rocket up from 75,000 in 2019 to 100,000 in 2020 in response to the procedure’s recent approval in low-surgical-risk patients with symptomatic aortic stenosis, Michael J. Mack, MD, said at the annual Cardiovascular Conference at Snowmass sponsored by the American College of Cardiology.
Bruce Jancin/MDedge News
Dr. Michael J. Mack
“In 2020, TAVR seems like a tsunami that’s totally overwhelming SAVR [surgical aortic valve replacement]. And the question is, after the wave hits shore, is there going to be anything left in the surgical arena?” asked Dr. Mack, who is medical director of cardiothoracic surgery and chairman of the Baylor Scott & White The Heart Hospital – Plano (Tex.) Research Center.
He answered his own question with a quote from Mark Twain: “Reports of my death are greatly exaggerated.”
The trend is clear: TAVR will take over the market for isolated aortic valve replacement in much the same way that endovascular abdominal aortic aneurysm repair (EVAR) has come to dominate open surgical repair by an 80:20 margin. And By one estimate, it could include some 270,000 individuals per year in North America and the European Union (Eur Heart J. 2018 Jul 21;39[28]:2635-42).
But there’s no need to shed a tear at the prospect of SAVR surgeons standing in unemployment lines. They will continue to have their hands full performing combined SAVR plus coronary artery bypass graft (CABG) procedures, SAVR plus mitral or tricuspid valve operations, and Bentall procedures, Dr. Mack predicted.
Who should get SAVR for aortic stenosis in 2020? For starters, he said, the sorts of patients who were excluded from the major TAVR-versus-SAVR randomized trials. The low-surgical-risk trials were restricted to patients who had symptomatic aortic stenosis involving a tricuspid valve, no left ventricular outflow tract calcium, no or minimal coronary artery disease (CAD), a relatively normal left ventricular ejection fraction, and an aortic valve anatomy suitable for TAVR. And, 92% of study participants were over age 65 years.
Dr. Mack called the evidence for the safety and effectiveness of TAVR “the most robust evidence base in the history of medical devices,” backed by nine U.S. trials and 8,000 randomized patients during the last dozen years. He has played a major role in developing that evidence base, having served most recently as cochair of the landmark PARTNER 3 trial, which demonstrated superiority for TAVR over SAVR in low-surgical-risk patients. But the evidence base doesn’t apply to patients not enrolled in the trials. So for the foreseeable future, patients younger than age 65 years should probably stick with SAVR, mainly because of the still-open question of tissue valve durability and TAVR’s high rate of associated conduction system impairment and need for new pacemaker implantation. Younger patients find permanent pacemakers particularly problematic, he noted.
Others who should stick with surgery include patients with bicuspid valves, especially when aortopathy is present, individuals with low-lying coronary arteries, patients with heavy calcium deposits at the left ventricular outflow tract, those with infective endocarditis or rheumatic valve disease, and patients with structural valve deterioration after a valve-in-valve TAVR.
“Once you get beyond the first valve-in-valve, the outcomes are not going to be good. Those patients should preferentially be considered for surgery. The results for valve-in-valve have been very disappointing, with a 33% all-cause mortality at 3 years in the PARTNER Aortic Valve-in-Valve Registry,” according to the surgeon.
In patients with aortic stenosis and CAD, the clinical decision making should be based on the coronary disease. In a patient with triple-vessel disease, diabetes, and/or a high Syntax score for whom the collaborative multidisciplinary heart team would recommend surgical revascularization if aortic stenosis wasn’t present, the most appropriate option is SAVR plus CABG. On the other hand, if the CAD is amenable to percutaneous coronary intervention (PCI) and the Syntax score is low, TAVR plus PCI is a safe and solid strategy, he continued.
In addition to the unresolved issue of tissue valve durability, another unanswered question pushing against universal adoption of TAVR involves the clinical implications of bioprosthetic valve leaflet thrombosis and the optimal antithrombotic therapy, both early and late. Leaflet thrombosis post-TAVR is common – as well as post-SAVR with bioprosthetic valves, albeit less so – but the lesions often come and go. Although there is a theoretical concern that they might be a precursor to leaflet destruction, at this point, their clinical significance remains unclear. In the recent GALILEO trial, TAVR patients randomized to low-dose rivaroxaban (Xarelto) plus aspirin showed fewer leaflet motion abnormalities and less leaflet thickening than did those on dual-antiplatelet therapy, but a significantly higher all-cause mortality (N Engl J Med 2020 Jan 9;382:120-9).
“I know that nowhere else in the body is thrombus a good thing, so thrombus in the valve can’t be a good thing. The only question is, how bad is it? And right now all we know is, some of our treatments for it are worse than the disease,” the surgeon commented.
Dr. Mack indicated that, at this time, clinical decision making in aortic stenosis should begin on the basis of patient age, which influences the key decision of whether to opt for a mechanical versus tissue replacement valve. For patients aged 50-70 years, shared decision making between the heart team and patient is appropriate. The evidence suggests SAVR with a mechanical valve is the better option, but many patients in this intermediate age group loathe the ideal of lifelong oral anticoagulation and favor a tissue valve.
For patients under age 50 years, the best evidence indicates that SAVR with a mechanical valve is clearly the best option; however, most young patients are instead opting for a tissue valve, even after being cautioned about the lingering uncertainty surrounding tissue valve durability, be it SAVR or TAVR. For patients over age 70 years, a tissue valve is the best choice based on the outcomes in PARTNER 3 and other low-surgical-risk trials. If the patient is younger than 65 years and wants a tissue valve, Dr. Mack thinks the best evidence-based option is SAVR. Above age 80 years, TAVR is the clear choice. Age 65-80 years is shared–decision making territory regarding TAVR versus SAVR.
Dr. Mack reported serving as a consultant to Gore and receiving research grants from Abbott Vascular, Edwards Lifesciences, and Medtronic.