How is a catheter used to replace a pulmonary valve?

During a catheter-based pulmonary valve implantation in the heart, a large catheter (a flexible tube) is placed in a central vein, usually in the leg, and advanced to the heart and the existing pulmonary valve. Separate wire cages (called stents) are usually inserted into a tube that was previously placed during open-heart surgery. Stents are very stiff and protect the tube from compressing the new valve. The current valve used in the United States comes from a cow’s jugular vein and is sewn into a stent. It looks and functions very much like a human valve.
This valve is placed the same way other stents are placed: the stent/valve is threaded to the procedure site in the heart via a catheter. A balloon at the end of the catheter is inflated to expand the stent/valve into place. Then the balloon is deflated and the catheter is removed, leaving only the stent/valve in the body. The new valve opens completely to let blood flow out freely and closes to prevent blood from leaking back into the heart.
Because of the large catheters placed in the vein, patients are usually watched in the hospital for a couple of days following the procedure to make sure the site where the catheter was inserted is healing well and will not bleed, as well as to make sure the changes to the blood circulation are tolerated well. Children and adults undergoing this procedure can usually return to normal activity within a few days.