麻豆传媒

PARIS -- Transcatheter replacement of failing bioprosthetic aortic valves is usually successful but likely should be left to the most expert hands, researchers suggested.

In a global registry of valve-in-valve procedures, 87.5% of the fairly high-risk cohort saw a reduction in symptom severity to New York Heart Association class I or II.

Survival rates were similar to what would be expected from transcatheter aortic valve implantation (TAVI) in native valves, Danny Dvir, MD, of Washington Hospital Center in Washington, D.C., and colleagues reported here at the EuroPCR meeting.

However, "the valve-in-valve procedure, although feasible, is technically demanding, includes several safety concerns, and should probably be reserved for highly experienced centers," Dvir said at a press conference.

Those hazards included:

• A high rate of initial device malposition, at 11.1%
• Clinically-evident ostial coronary obstruction in 1.9%, with five deaths among the eight cases
• Need for an emergent surgery in 1.9%

Bioprosthetic valves typically last 10 to 15 years, and when they do fail the "redo" operation is high-risk, Dvir explained.

TAVI is considered a less invasive and possibly safer alternative, but the data on that has only come from small case series.

Dvir's registry study included all 420 such procedures done at 54 centers in North America, Australia, Europe, the Middle East, and New Zealand.

The reason for bioprosthetic valve failure was fairly split among mechanisms, with 40% stenotic, 30% having regurgitation, and the rest with a moderate and comparable degree of both problems.

All-cause mortality at 30 days after the valve-in-valve procedure was:

• 10.9% for patients whose valves had failed due to stenosis
• 4.1% for patients who needed a replacement due to valve regurgitation
• 6.7% for patients with both mechanisms of valve failure

Cardiovascular mortality rates at 30 days were 9.8%, 3.3%, and 5.8%, respectively (P=0.08 for difference among groups).

The strongest predictor of 1-year survival after the valve-in-valve procedure was mechanism of valve failure. The difference in risk between stenosis as the mechanism of valve failure compared with regurgitation or both, was 3.7- and 7.1-fold, respectively.

The stroke rate was low, at around 2%.

But a common problem was modestly-elevated gradients in blood flow across the valve after the replacement procedure, suggesting narrowing or blockage in flow. Pressure differences were more than 20 mmHg in 29% of cases and more than 40 mmHg in 3%.

Whether these gradient elevations are meaningful isn't clear yet, Dvir noted.

"The impact on valve viability should be evaluated in the long term," he said at a press conference.

The risk of this kind of blockage appeared 2.1-fold lower with the Medtronic CoreValve than with the Edwards Sapien valve (approved in Europe but not the U.S. or Canada).

The problem appeared largely with Sapien valves 20 mm or less in internal diameter.

That hints at the probable reason for the difference between the valves. The functional part of the Sapien valve is in the level of the annulus of the native valve, whereas it sits higher in the CoreValve bioprosthesis, Dvir pointed out.

"New transcatheter aortic valve replacement devices dedicated for valve-in-valve procedures should be developed, enabling treatment of small bioprosthetic valves with improved efficacy and safety," Dvir said.

Clinical trials would be nice, too, but there may not be the patient numbers to support them, he noted.

For now, "people need to know their valves," argued study discussant John Webb, MD, of the University of British Columbia in Vancouver. Many interventionalists don't have a good understanding of surgical valves, although this impacts the size of the bioprosthesis that can go inside and likely contributed to the "disturbingly" high rate of malposition, he said.

And those surgical valves are what usually need replacing, since TAVI is new enough that almost none have worn out yet.

The internal diameter of the Sapien valve is likely smaller, though dimensions are usually reported in terms of the external diameter, which may account for the difference in elevated gradients between stent types, he noted.

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