BACKGROUND: Valve-in-valve transcatheter aortic valve replacement (VIV TAVR), while an approved option for high-risk patients, carries an increased risk for patient-prosthesis mismatch (PPM), particularly when performed in small surgical valves. Bioprosthetic valve fracture (BVF) and bioprosthetic valve remodeling (BVR) can mitigate PPM by either fracturing or remodeling the surgical valve thus allowing the implanted transcatheter heart valve (THV) to more optimally expand.
METHODS:In initial bench testing (pre 2018), Mosaic (Medtronic, Santa Rosa, CA) valves could be fractured, however, we now understand that the Mosaic valve can be manufactured with one of two different polymer rings: either Delrin (acetal homopolymer resin), in which case the ring can be fractured at approximately at 10-12 atmospheres, or PEEK (polyetheretherketone), in which case the ring cannot be fractured but it can be remodeled. Mosaic valves manufactured with PEEK will remodel/stretch in response to a high-pressure balloon inflation, with maximal expansion at 18-20 atmospheres. Unfortunately, there is no information readily available regarding which polymer is present in any given Mosaic valve.
RESULTS: The following case illustrates this important new information and how to perform VIV-TAVR in Mosaic valves. A 97-year-old woman was referred with low-flow, low-gradient aortic stenosis (mean gradient 29 mmHg which augmented to 49 mmHg with dobutamine) and a failed 23 mm Mosaic valve (true internal diameter 19mm) Anticipating either BVF or BVR, a larger 23 mm Sapien 3 Ultra (Edwards, Irvine, CA) was implanted (Figure A), which as expected, resulted in a constrained THV with severe PPM (residual mean gradient 26 mm). A 23 mm True balloon (Bard, Tempe, AZ) and high-pressure inflation was then initiated and steadily increased to ~12 ATM which if the Mosaic valve was made of Delrin fracture would have occurred. In this case, by 14 ATM there was no indication that fracture had occurred (sudden drop in indeflator pressure and/or an acute release of the waist of the true balloon) suggesting that this Mosaic valve was manufactured with PEEK. Knowing this prompted a continued increase in the indeflator pressure to 20 atm which resulted in a gradual expansion of the surgical valve ring until resolution of the ‘waist’ of the balloon was observed (Figure B). Final result was a perfectly expanded 23 Sapien with a final mean gradient of 3 mmHg (Figure 1A)
CONCLUSIONS: Knowledge by the Heart Team that Mosaic valves can respond differently to high-pressure balloon inflation by either fracturing or remodeling depending upon which polymer the annulus is manufactured with is essential to optimizing the hemodynamic results of VIV TAVR with this particular surgical valve.
