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CHICAGO -- The latest trial in the PARTNER series of transcatheter aortic valve replacement (TAVR) trials affirms the technique's non-inferiority to surgery for patients with symptomatic aortic valve stenosis.

The first PARTNER study tested TAVR in patients who were too sick or too old for surgery, and those results confirmed the safety of replacing an aortic valve via catheter. Those results were quickly followed by a second study that compared TAVR with surgery in high-risk patients in whom surgery could safely be performed and again TAVR was found to be non-inferior.

This time around the PARTNER-2 investigators, again led by interventional cardiologists , of Columbia University, report that when TAVR was compared with surgery in intermediate-risk patients, there was no difference in the rate of death or stroke at 2 years.

The results were reported as a late-breaking clinical trial at the American College of Cardiology meeting here by Columbia University surgeon Craig R. Smith, MD, and simultaneously published online by .

All of the PARTNER studies used valve systems from Edwards Lifesciences and in this study the SAPIEN XT valve system was implanted, which has now been replaced in U.S. practice by the Sapien 3, more commonly referred to as the S-3 system.

The reassuring results do not, however, make a case for TAVR to replace surgery in all patients, since the intermediate risk patients in this trial, while considered lower risk than the patients in previous studies, are nonetheless "among the highest risk-quintile of patients with aortic stenosis who are candidates for surgery in the United States and elsewhere," Leon and colleagues noted.

Moreover, Valentin Fuster, MD, of Mount Sinai Heart, cautioned that aortic valve disease is complex covering a wide range of anatomy, most of which have not been included in the current TAVR studies. Fuster, who is Editor-in-Chief of the Journal of the American College of Cardiology, moderated the press conference where the PARTNER 2 results were discussed.

The investigators randomly assigned 2,032 patients, with symptomatic aortic stenosis, to 57 participating centers for either TAVR or surgery. Just over half of the patients in each arm were men and the average age was 82.

The primary endpoint was death or disabling stroke at 2 years. Among the 1,011 TAVR patients the rate of death or disabling stroke was lower than in the 1,021-patient surgery group, for a hazard ratio of 0.79, 95% CI 0.62-1.00, P=0.01.

In this trial, as in earlier studies, TAVR looked best when it was performed transfemorally -- so good that it may be superior to surgery, but the authors cautioned that this suggestions of superiority would need to be confirmed in a superiority trial. Results from transthoracic TAVR were problematic, and were sometimes worse than surgery. In the trial, 236 patients in the TAVR group had transthoracic access, of which 174 underwent transapical procedures.

"At 30 days , major vascular complications were more frequent in the TAVR group than in the surgery group, (7.9% vs 5.0%, P=0.008)," they wrote. On the upside, life-threatening bleeding, acute kidney failure, and new onset atrial fibrillation were more common with surgery and the differences were highly significant.

Fuster questioned the life-threatening bleeding events in the surgery arm, noting that it was much higher than he has seen in surgical aortic valve repair.

Smith said transfusion was used as a marker for bleeding, a decision that may have overstated the true bleeding risk, noting "it is not a term I would have chosen ... depending upon which side of the debate you stand, you may want to make it sound more alarming."/p>

As in earlier studies, there was a greater "increase in valve areas with TAVR than with surgery" and the most likely explanations for this difference were "valve-sizing differences and the ability of transcatheter valves to expand to the anatomical annulus size, which is not possible with a fixed-size surgical sewing ring."

The risk of paravalvular aortic regurgitation is known to be greater with TAVR, but in this latest trial the rate was less than 4% at 30 days, and "unlike findings in previous PARTNER trials, only moderate or severe, but not mild, paravalvular aortic regurgitation was associated with higher subsequent mortality."

Last fall some researchers reported a finding a subclinical valve-leaflet thrombosis which was detected using high-resolution imaging, but that was not assessed in this trial and is therefore a limitation.