Balloon-expandable valve implantation is limited by conduit or landing zone size. Stepwise balloon dilations can expand or fracture small conduits for 20–22 mm Melody valve placement. ^{Reference Hascoet, Martins and Baho1} The Melody can also be undersized for atrioventricular use in infants, but its expandability remains uncertain. ^{Reference Pluchinotta, Piekarski and Milani2} The Sapien S3 shows potential, though concerns persist about underexpansion and untested overexpansion. ^{Reference Maschietto, Prakash and Del Nido3}

MyVal OCTACOR valves (Meril) feature a two-row octagonal design, reducing foreshortening, and enabling further expansion. ^{Reference Kilic, Coskun, Mirzamidinov, Yilmaz, Yavuz and Sahin4} We tested 20 and 29 mm valves in 3D-printed silicone tubes using a low-pressure, water-perfused simulator with ultrasound and video monitoring, across diameters 4–6 mm below and above nominal (Vid. 1). Leaflet motion and Doppler flow were assessed.

The 20 mm valve showed mild asymmetric underexpansion but maintained laminar flow at 16 mm, improved at 18 mm, normalised at 22 mm, developed central regurgitation at 24 mm, and leaflet rupture with severe insufficiency at 27 mm (Figure 1, Vid. 2). All inflations were low-pressure. The 29 mm valve had laminar flow at 23 mm despite limited opening, which improved at 25 and 27 mm. Under 4 atm, the valve expanded to 32 mm and showed a mild central coaptation defect and insufficiency (Vid. 3). No further expansion was possible beyond 33 mm (Figure 2).

Figure 1.

20 mm MyVal OCTACOR valve under-expanded at 16 mm, then dilated at 18, 22, 24, and 27 mm.

Figure 2.

29 mm MyVal OCTACOR valve under-expanded at 23 mm, then dilated at 25, 27, 32, and 33 mm.

Pending clinical data, these findings suggest that MyVal OCTACOR valves may reduce the need for repeated open-heart surgeries by allowing multiple valve-in-valve procedures over a lifetime. This advantage appears more pronounced in smaller sizes (20 mm), while larger sizes (29 mm) show limited expansibility. Preserved function of the 20 mm valve across a wide range of diameters may support its use in the mitral position for small infants as an alternative to the Melody valve.