closed by welding the ends the two rings are placed on top of each other as will appear from fig1 and they are mutually secured by means of a number of sutures not shown the lower ring is circumferentially expandable at least along sections thereof which correspond to the circumferentially expandable sections 25 by using a substantially cylindrical thread structure with projecting apices a reduction in weight is obtained as compared to a stent which is exclusively cylindrical with the same loop heights for all the loops the biological valve 6 was removed from a slaughtered pig of 100 kg the valve was cleaned before mounting in the stent 1 the cleaned valve has an outer diameter of 25 27 mm and the height of the three commissural points 5 is 8 mm the valve 6 is mounted in the stent by means of a suitable number of sutures to form the cardiac valve prosthesis 9 shown in fig2 the valve prosthesis produced is used for performing tests in pigs by implantation of cardiac valve prosthesis however the cardiac valve prosthesis for use in human beings has a corresponding form fig3 shows a partial view through the aorta 10 a balloon catheter 11 is introduced in the aorta according to the direction of an arrow 12 in the figure shown the balloon means 13 of the balloon catheter is led out of the protection cap 11a and is partly inflated through a fluid channel 15 which is led to the surface of.