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CHICAGO -- Transcatheter aortic valve replacement (TAVR) again demonstrated non-inferiority to surgery, but this time the comparison was in a lower risk population.

At 2 years, rates of death or disabling stroke were similar between TAVR recipients and surgery patients (P=0.001 for non-inferiority) in the PARTNER 2 trial. Event rates were no different between groups (19.3% for TAVR versus 21.1% for surgery; hazard ratio [HR] 0.89, 95% confidence interval [CI] 0.73-1.09).

TAVR via transfemoral access, compared with surgery, was associated with a lower rate of either outcome however (16.8% versus 20.4%, HR 0.79, 95% CI 0.62-1.00). Trans-thoracic TAVR did not exhibit a similar advantage, according to , of New York Presbyterian/Columbia University Medical Center, and colleagues.

"Our findings of the noninferiority of TAVR to surgery were robust, with similar between-group outcomes for the end points of death and stroke and with consistency across all the subgroups tested," the authors reported online in the New England Journal of Medicine as well as in a presentation at the American College of Cardiology (ACC) 2016 Scientific Sessions on Tuesday morning.

Of note, "the possible superiority of TAVR over surgery in the transfemoral-access cohort is a new finding for balloon-expandable transcatheter valves. It requires prospective evaluation in a suitably powered superiority study. If this finding is confirmed, it probably reflects increased operator experience and the effect of a low-profile enhanced TAVR system combining to reduce procedure-related complications," Leon's group wrote.

For , of Royal Brompton Hospital in London, PARTNER 2 appeared to confirm that TAVR is the "treatment of choice" in most patients with aortic stenosis who are at high risk for early death and major complications from conventional surgery.

Nevertheless, Moat suggested, cost remains a crucial question.

"In previous trials, TAVR has been shown to be cost-effective. It is uncertain whether this finding will still hold true in low-risk patients (in whom the cost of conventional surgery is substantially less) unless the current device costs are reduced," he wrote in an accompanying editorial.

, of The Mount Sinai Hospital in New York, also told 番茄社区app that "we see many patients with aortic valve stenosis that are not amenable to TAVR not because they are very high risk" -- but because of other complicating factors.

Bicuspid aortic valves, valve incompetence, and calcification near the valve remain challenges no matter the patient's surgical risk profile, suggested Fuster, and that appears to be the case for about 25 to 30% of aortic valve stenosis cases.

Even so, Fuster -- who was not involved in the study -- maintained that Leon's trial was "impressive" and indicated that TAVR is moving closer to people with low surgical risk.

The randomized, prospective study included 2,032 patients in cohort A with severe aortic stenosis who fit a intermediate-to-high risk clinical profile while remaining in the highest quintile of risk. TAVR was performed using the SAPIEN XT valve system, with 76.3% of the TAVR group receiving the intervention via transfemoral access, and 23.7% via transthoracic access.

Patients receiving TAVR also had more pronounced improvement in aortic valve area after intervention, as well as reduced rates of acute kidney injury (3.8% versus 6.2%, P=0.02), severe bleeding (17.3% versus 47.0%, P<0.001), and new-onset atrial fibrillation (11.3% versus 27.3%, P<0.001).

In contrast, surgery conferred fewer major vascular complications (8.6% versus 5.5% for TAVR, P=0.006) and less paravalvular aortic regurgitation (P<0.001).

"The risks of all major complications with TAVR affecting late mortality were lower in this trial than in earlier randomized trials," according to Leon and colleagues.

Even so, they acknowledged that even longer-term data -- through 10 years -- will be needed to assess the durability of bioprosthetic transcatheter valves. Five-year findings from earlier PARTNER studies "indicate no evidence of important premature or accelerated structural valve deterioration," however.

The investigators also noted that their conclusions were limited by their sole use of the SAPIEN XT. "Further technological advances may favorably influence the outcomes with TAVR in the future, and the SAPEIN XT valve that was used in this trial has already been replaced by the SAPIEN 3 valve system."

Moat agreed, writing that "new TAVR devices with lower-profile delivery systems have increased the proportion of patients who can be treated with a transfemoral approach and have significantly reduced the incidence of moderate or severe paravalvular leak. Furthermore, the use of cerebral-protection devices may reduce embolic risk among patients undergoing TAVR."

Yet technological advances do go both ways, the editorialist suggested, as surgery with the use of sutureless devices has "reduced the invasiveness of surgery and enlarged the post implantation valve area" as well.

For now, the message remains clear that for patients at intermediate-t0-high risk, "TAVR is noninferior to surgery in terms of early and midterm mortality and is likely to be superior if the patient has vascular anatomy and vessels that are healthy enough to be treated with the use of a transfemoral approach," he concluded.

Moat pointed to SURTAVI and UK TAVI as new studies to watch out for when it comes to TAVR outcomes in intermediate-risk patients.