maybe this will help Deb
maybe this will help Deb
Valve Replacement
If valve disease is very severe, then the only alternative that provides the patient with a reasonable prognosis is surgical replacement. The surgeon cuts out the leaflets and may modify the annulus. Then a replacement cardiac valve prosthesis (types discussed briefly below) is sewn into position. These valves fall into two main categories; bioprosthetic and mechanical. Bioprosthetic valves are usually formed of either a porcine (pig) aortic valve or from the pericardium (fibrous sac that surrounds the heart) of a cow (bovine) that has been chemically treated. The chemical treatment prevents the host's body from destroying the valve via an immune response. Bioprosthetic valves have the advantage that they do not require that the patient take any chronic drug therapy, and when they do fail they provide ample warning time. However, these tissue valves do not last forever. Their service life is dependent on the age of the patient, patient health and other factors we don't yet understand. This means that patients receiving a bioprosthetic valve face the possibility of requiring a replacement reoperation. For this reason bioprosthetic valves are usually implanted into older patients, generally 60+, and sometimes young women of childbearing age. Bioprosthetic valves currently in use include the Carpentier-Edwards pericardial, Carpentier-Edwards porcine, Hancock II and others.
Mechanical valves are very durable - in most cases they will last as long as needed - but cause other problems. Because they are made of rigid man-made materials, they damage the blood as it flows past. Also, some blood may clot on the surface of the valve, and if it breaks free may cause heart attack or stroke. To reduce the incidence of this, patients who receive mechanical valves take anticoagulation drugs chronically to reduce the ability of their blood to clot. The drug is called sodium warfarin (commercially called Coumadin® by DuPont-Merck) and must be monitored carefully to ensure that the patient doesn't receive too much or too little. The problem with anticoagulant therapy is that is makes the patient a borderline hemophiliac. As a result, patients often have to curtail some physical activities to reduce the chance of an injury. Since the blood's ability to clot is reduced, a bruise or bad cut can be life threatening. The most popular mechanical valves are made of pyrolitic carbon and have names such as St. Jude Bileaflet, Medtronic-Hall tilting disk and Starr-Edwards ball-and-cage, among others. The best valve for any individual is determined by the patient's age, sex, level of physical activity and personal preference. Unfortunately the perfect cardiac replacement valve has not yet been invented, but the existing devices provide people suffering from severe heart valve disease an opportunity to enjoy a high quality of life.
