Abstract: A heart valve stiffening ring of this disclosure includes a split ring that allows assembly over a channel-shaped heart-valve-orifice-forming angular heart valve body, with the split ring having an outer peripheral tapered thread, which allows adjustment of pressure between the split ring and the orifice-forming annular body. A solid ring or nut has complementary tapered threads to mate with the outer peripheral tapered thread of the split ring and is adjustable for tightening of interfit thereof to bring about correct pressure for desired tightening effect with a moment of inertia in bending of the outer channel to make the orifice stronger so that orifice outer diameter thereof can be a maximum value. The angle of taper is substantially 3 degrees with respect to the center line. This heart valve stiffening ring can be employed in place of a heart valve locking ring of U.S. Design Pat. No. 376,206-Reif issued Dec. 3, 1996.