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Those considering transcatheter valve-in-valve (ViV) implantation for a patient's failing surgical aortic valve should be on the lookout out for prosthesis-patient mismatch, researchers said, because it could raise the risk for complications.

A surgical valve that was already too small upon placement may partly explain poor survival following a subsequent ViV procedure: 30-day mortality rates were 10.3% for those with existing severe prosthesis-patient mismatch versus 4.3% for those without (P=0.01), according to Philippe Pibarot, DVM, PhD, of Canada's Institut Universitaire de Cardiologie et de Pneumologie de Québec, and colleagues.

Death climbed to 19.3% and 10.9%, respectively, at 1 year (P<0.001). Statistical adjustment confirmed an almost-doubling in mortality risk when ViV was performed on someone with mismatch (OR 1.88, 95% CI 1.07-3.28), they reported in.

Their data came from 1,168 patients in the international VIVID registry, 7.6% of whom had pre-existing severe prosthesis-patient mismatch.

"Pre-existing prosthesis-patient mismatch of the failed surgical valve is strongly and independently associated with increased risk for mortality following ViV implantation," they wrote. "These findings also support the systematic integration of the assessment of pre-existing prosthesis-patient mismatch in the risk stratification and decision-making processes before ViV implantation. This can easily be achieved by calculating the predicted indexed EOA [effective orifice area]."

Moreover, mismatched patients were more likely to have high residual gradients a year after the procedure (47.5% versus 29.6%, P=0.001).

"The ViV procedure generally improves the hemodynamic and clinical status of patients who have acquired dysfunction resulting from structural valve degeneration. However, prosthesis-patient mismatch is a nonstructural 'iatrogenic' complication that is characterized by a prosthetic valve with normal function but that is too small in relation to the body size and thus to the cardiac output requirements of the patient," Pibarot's group wrote.

"Hence, given that the stent and internal orifice diameter of surgical bioprosthetic valves are generally not expansible, the ViV procedure cannot correct pre-existing prosthesis-patient mismatch, and in fact, this procedure may even worsen the prosthesis-patient mismatch. Indeed, the implantation of a transcatheter heart valve within a severely mismatched bioprosthetic valve may further reduce the already limited valve orifice area available for flow," they noted.

Mismatch is a major contributor to leaflet mechanical stress, which in turn may factor into structural degeneration of the bioprosthetic valve. For the purposes of the study, the authors defined severe prosthesis-patient mismatch as predicted indexed EOA smaller than 0.65 cm²/m² if BMI is <30 and smaller than 0.6 cm²/m² if BMI is at least 30.

Susheel Kodali, MD, and Vinayak Bapat, MD, both of Columbia University Medical Center/New York-Presbyterian Hospital in New York City, suggested doing transcatheter aortic valve replacement upfront in lieu of surgery to lower the likelihood of mismatch.

"Although efforts should be made to avoid surgical prosthesis-patient mismatch, this will not be feasible in all cases," they acknowledged in an accompanying editorial. "The question remains what to do when patients with severe prosthesis-patient mismatch present with bioprosthetic valve failure."