ACC 2019: TAVI moves to the mainstream with new findings in low-risk patients

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Evidence for the use of transcatheter aortic valve replacement (TAVI) as standard therapy is mounting, with the release of data from two major new studies that demonstrate its role in low-risk patients. Both were presented at late breaking trial sessions at the American Congress of Cardiology annual scientific session (ACC 19) in New Orleans, USA (16–18 March) and simultaneously published in the New England Journal of Medicine. The studies increase the prospect that its use will be approved in these patients.
PARTNER 3 found a significantly lower risk of death, stroke and rehospitalisations at one year with transfemoral valve replacement than with open surgery among patients who had severe aortic stenosis and who were at low risk for surgery. And the Evolut Low-Risk trial determined that, for patients with severe aortic stenosis at low surgical risk, TAVI with a self-expanding bioprosthesis was non-inferior to surgical aortic valve replacement for death or disabling stroke at two years.
PARTNER 3 randomly assigned 950 patients 1:1 either to surgery or to transfemoral placement of a balloon expandable valve (Sapien 3, Edwards LifeSciences). Average age was 73 years, and 30% of patients were female. The primary endpoint was a composite of death, stroke, and rehospitalisations at one year. Among the secondary endpoints were new onset atrial fibrillation, need for new permananent pacemaker, and length of stay.
Michael Mack (Baylor Scott & White Health Heart Hospital, Plano, TX, USA) and his co-investigators describe the findings as robust. Multiple sensitivity analyses confirmed that TAVI via the transfemoral route with a Sapien 3 balloon expandable system was superior to surgery for a composite endpoint of death, stroke, or rehospitalisations at one year (8.5% vs. 15.1%, respectively). TAVI was also associated with a significantly lower rate of new onset atrial fibrillation than surgery at 30 days (5% vs. 39.5% in surgical patients, hazard ratio [HR] 0.10, p<0.001), a shorter index hospitalisation (three days vs. seven days, respectively, p<0.001), and a lower risk of a poor treatment outcome (death or a low Kansas City Cardiomyopathy Questionnaire [KCQQ] score, 3.9% vs. 30.6%, respectively, p<0.001). In addition, patients who had transcatheter treatment had more rapid improvement in New York Heart Association (NYHA) class, six-minute walk test distance, and Kansas City Cardiomyopathy Questionnaire score than patients who had surgery.
Mack et al also point out that complications shown to be more frequent with TAVI than surgery in previous trials occurred with similar frequency in both groups in the PARTNER 3 study. However, they acknowledged that, with only one year of follow-up data, the trial does not address the issue of long-term structural valve deterioration: “Definitive conclusions regarding the advantages and disadvantages of TAVI as compared with surgery (with either bioprosthetic or mechanical valves) depend on long-term follow-up. In this trial involving younger, low-risk patients, the protocol requires clinical and echocardiographic follow-up to continue for at least 10 years.”
Evolut was a multinational randomised non-inferiority clinical trial that compared the safety and efficacy of transcatheter aortic valve replacement with surgical replacement in 1,468 patients with severe aortic stenosis considered to be low risk at 30 days for surgery. Randomisation was 1:1, and the patients assigned to transcatheter replacement were treated with either CoreValve, Evolut R, or Evolut Pro (Medtronic); the surgical valve was determined at surgeons’ discretion. Patients were evaluated at baseline, discharge, one, six, 12, 18, and 24 months. Primary safety and efficacy endpoints were a composite of death from any cause or disabling stroke at two years.
Mean age of patients was 74 years and 34.9% were female, with no demographic differences between the two treatment cohorts. At two years, the incidence of death or disabling stroke was 5.3% in the transcatheter group and 6.7% in the surgery group. The 24-month estimated incidence of death from any cause was 4.5% in both groups, and disabling stroke was 1.1% in the TAVI group and 3.5% among patients who had surgery. No significant treatment by subgroup interactions were observed for the primary endpoint.
Writing in the NEJM, researchers Jeffrey J. Popma (Beth Israel Deaconess Medical Centre, Boston, MA, USA) et al conclude: “Our study showed that among patients deemed to be at a low risk for death from surgery, TAVR [transcatheter aortic valve replacement] with a self-expanding supra-annular bioprosthesis was non-inferior to surgery with respect to the risk of death or disabling stroke at 24 months. The estimated 24-month incidence of death from any cause was low (4.5%) in both groups, a finding that reinforced the fact that our study included healthier patients with severe aortic valve disease.”
TAVI was also associated with a lower risk of disabling stroke, acute kidney injury, bleeding events and atrial fibrillation than surgery, but with a higher incidence of aortic regurgitation (3.5% vs. 0.5%) and pacemaker use (17.4 vs. 6.1%). Both therapies provided functional improvement at 12 months, but transcatheter replacement led to better recovery at 30 days. At 12 months, patients who underwent TAVI had lower aortic valve gradients than those who had surgery (8.6mmHg vs. 11.2mmHg) and larger effective orifice areas (2.3cm2 vs. 2cm2).
Speaking to Cardiovascular News, Popma describes the valve haemodynamics as “spectacular”, and said there was a trade-off with pacemaker rates, which he expects to fall: “We only had about 25% of patients who were treated with our newest generation device, and we are still evolving to do better and we will do better with lowering the pacemaker rate, no question.”
He hails the trials as “an overwhelmingly positive day for TAVI. This is a huge advance forward. Both sets of trials had phenomenal results; they had spectacular surgery and TAVI beat that with both of them. Both of these valves perform exceedingly well versus surgery in a low-risk population of patients.” He says a cross-trial comparison is difficult, but that although both studies had differing primary endpoints and were set to do different things, there was no real difference between them.
Mack told Cardiovascular News the findings would change risk assessment: “The criteria will now switch from risk for surgery to risk for TAVI, which will primarily be anatomical problems. Patients most appropriate for surgery will be bicuspid aortic valves, low-lying coronary arteries, inadequate femoral access and significant left ventricular outflow tract calcium. Most younger patients (<65 years) will still stay with surgery until long term durability questions are answered. I would guess that within a few years, approximately three out of four patients will be treated with TAVI.”
And he predicts a change in the recommendations for low-risk patients: “With two randomised trials both being positive, I think it is highly likely that they [transcatheter valves] will be approved later this year.”
His comments are echoed by the investigators of a third study—LRT 1, a prospective multicenter investigator-initiated trial which found that TAVI using commercially available valves is safe and effective in low-risk patients, with low adverse event rates and excellent valve haemodynamics at one year. Ron Waksman (MedStar Washington Hospital Center, Washington DC, USA) presented the data at Cardiovascular Research Technologies (CRT) 2019 (2–5 March, Washington DC, USA), and recommended that if its findings were corroborated by the PARTNER 3 and Evolut trials “TAVI should be approved for low-risk patients”.

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