Mechanical (Prosthetic) Valves
There are a number of different brands (St. Jude, ATS, On-X, Carbomedics, Medtronic, etc.), although all have in common at least one artificial valve leaflet that opens and closes passively with the flow of blood across the prosthesis. Most fit into the category of bileaflet (two artificial leaflets) valves housed within a circular stent, and associated sewing ring, which is used to secure the prosthesis to the aortic valve ring at the time of valve replacement. The durability with all available mechanical prosthesis is very good with very few valves requiring replacement later.
Because the artificial valve leaflets act as a foreign prosthetic surface inside the circulation, it is mandatory that recipients are placed on anti-coagulants (Warfarin, Coumadin), in order to prevent blood clots forming on the valve prosthesis, which could prevent the leaflets from opening, or break off and travel to other sites in the body, e.g. the brain (by which they would cause a stroke or localised damage to the brain). Patients with mechanical valves must remain on Warfarin life long, and have blood tests performed every two to four weeks, to ensure their blood is prevented from clotting “to the correct degree”.
Certain other factors can interact with the Warfarin dosage, and these includes dietary factors, administration of other medications or drugs, and other intercurrent illness. Whilst taking Warfarin or Coumadin, there is a small ongoing risk of blood clot migration problems (embolisation), as well as bleeding risks associated with being on Warfarin. Other major operations which may need to be performed at a later date (non-cardiac operations), can be performed, although there is a documented increase in risk of complications, because patients are on Warfarin.
Applicable Age Range (20 – 75)
- Durability – These valves are the most durable of all available prostheses, with 20 year freedom from re-operation of 90%.
- Easy Insertion – These valves can be inserted easily in a reasonably straightforward manner.
- Availability – “on shelf”.
- Warfarin necessity life long.
- Ongoing hazard of Warfarin and other valve-related complications.
- Increased risk for subsequent non-cardiac surgery.