Further Hazards of Mismatched Surgical Aortic Valve Prostheses

January 18, 2018

QUEBEC CITY — The mortality risk posed by transcatheter valve-in-valve (ViV) procedures goes up when the failed prosthesis from prior surgical aortic valve replacement (AVR) was mismatched in size compared with the patient's body surface area, suggests a registry analysis.[1]

Such prosthesis–patient mismatch (PPM), when post-AVR hemodynamics aren't sufficient for the patient's cardiac output demands, is already known to compromise the structural integrity of the AVR prosthesis and worsen clinical outcomes, observe the authors of the new analysis, published January 15 in JACC: Cardiovascular Interventions.

Their new observations suggest that this prosthesis mismatch at surgical AVR, should that valve ever fail, can also worsen survival after a future transcatheter ViV procedure that might otherwise have been the best treatment option.

Severe PPM at surgical AVR in the current series of more than 1000 patients undergoing a later transcatheter ViV procedure was associated with significant increases in 30-day and 1-year mortality compared with ViV procedures when there hadn't been such mismatch.

"When you do a valve-in-valve procedure, the prosthesis within which you're putting the valve has an important impact on the hemodynamic, functional, and clinical outcomes," lead author, Dr Philippe Pibarot (Institut Universitaire de Cardiologie et de Pneumologie de Québec, QC) told theheart.org | Medscape Cardiology.

In patients suspected of having surgical prosthetic valve failure who are evaluated by echocardiography, he said, it's important to determine whether any increased transvalvular gradient is due to degenerative disease or perhaps to PPM.

"If you have a severe regurgitation or severe stenosis, the valve-in-valve will help," Pibarot said. But options are more limited if it's a functioning but mismatched valve.

"If it's pure mismatch, or predominantly mismatch, then we have to consider that the treatment may actually be futile, or eventually harmful."

The message for surgeons with patients undergoing AVR, he said, is to choose a prosthetic valve that will optimize cardiac output by having the largest effective orifice area (EOA) possible for the size of the patient, the latter measured as body surface area.

As more surgeons have learned this, and with improvement in the design and selection of commercial prosthetic valves, the prevalence of new cases of PPM has declined, according to Pibarot.

"Having said that, there are many people out there with severely mismatched valves that were implanted a long time ago. So we still have a large population to treat with valve-in-valve where we can have this situation."

Surgeons choosing a prosthesis for AVR, according to an accompanying editorial,[2] must make sure the surgical outcome allows for a transcatheter ViV procedure in the future, should one be needed.

"This means ensuring PPM is minimized, and larger surgical prostheses (23 mm or larger) are utilized except in rare circumstances," write Drs Susheel K Kodali and Vinayak N Bapat (Columbia University Medical Center/New York–Presbyterian Hospital, NY).

If it's not possible to use a larger prosthesis, then transcatheter AVR, which is less likely than surgical AVR to result in PPM, "should be considered" for the initial procedure, they write. 

In the current series of 1168 patients in the Valve-in-Valve International Data (VIVID) registry, the report states, 7.6% had severe PPM at surgical AVR, defined as a prosthesis with an indexed EOA less than 0.65 cm2/m2 for patients with a BMI less than 30 kg/m2 and less than 0.6 cm2/m2 for those with a BMI of 30 kg/m2 or greater (consistent with Valve Academic Research Consortium 2 criteria).

Table. Unadjusted Outcomes of Transcatheter ViV Procedures by ProsthesisPatient Mismatch Status

Endpoint Severe PPM (%) No or Moderate PPM (%) P Value
Elevated post-ViV gradient 47.5 29.6 0.001
30-d mortality 10.3 4.3 0.01
1-y mortality 28.6 11.9 <0.001

 

The hazard ratio (HR) for 1-year post–ViV-procedure mortality for severe PPM at the prior surgical AVR was 1.88 (95% CI, 1.07–3.28; P=0.03) compared with no mismatch or only moderate mismatch, after adjustment for surgical prosthesis valve size as listed on the label, Society of Thoracic Surgeons risk score, renal failure, diabetes, and whether the surgical valve was stented or stentless.

In some cases, Pibarot said, a conventional transcatheter ViV procedure isn't a good option because of, for example, the presence of both severe disease and PPM.

For such patients considered too high-risk for another surgery, he said, operators are increasingly performing a ViV procedure that widens the final EOA by using a high-pressure noncompliant balloon that can fracture the constrictive stent frame of the implanted prosthetic valves.

But "if you have severe prosthesis–patient mismatch, and you're not sure you can fracture the stent, it's not a good candidate for a valve-in-valve."

The editorial agrees that fracturing the surgical valve to facilitate expansion of the surgical valve at a ViV procedure is an option. "However, the safety and feasibility of this procedure is not well established," and the effect of high-pressure balloon inflation on the long-term durability of transcatheter heart valve leaflets is not known.

Pibarot discloses receiving research grants from Edwards Lifesciences and Medtronic; none of the other authors have disclosed relevant financial relationships. Kodali discloses serving on a steering committee for Edwards Lifesciences and Medtronic, on a scientific advisory board for Dura Biotech and Thubrikar Aortic Valve, and as a consultant for Biotrace Medical and Claret Medical. Bapat discloses consulting for Edwards Lifesciences and Medtronic.

Follow Steve Stiles on Twitter: @SteveStiles2. For more from theheart.org, follow us on Twitter and Facebook.

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