Prosthetic valve and method of making a prosthetic valve

A prosthetic heart valve that can take a first form wherein the valve is open and a second form wherein the valve is closed, the valve comprising:

• a leaflet assembly having three leaflets attached to a supporting element at respective first and second commissures, the leaflets having a free margin that can move between a first position wherein the valve takes the first form and a second position wherein the valve takes the second form with each leaflet acting as a closure surface for the other leaflets, wherein
• the leaflets can form a coaptation height in a longitudinal direction of the valve of between 1 and 15 mm along the free margin without a pulsatile load on the valve and without requiring substantial extension of the leaflets, wherein
• the free margin of each leaflet has excess length relative to a minimum length needed to bridge a distance between the end of the leaflet's free margin at the first commissure to the end of the leaflet's free margin at the second commissure via the center of the valve, and wherein
• the leaflets comprise an elastic sheet material having an elongation at break of 10% or less.