The tissue component of bioprosthetic valves is treated ex vivo in such a way as to greatly reduce the immune reactivity. It's practically not a consideration.

The tissue component of bioprosthetic valves is treated ex vivo in such a way as to greatly reduce the immune reactivity. It's practically not a consideration. Mechanical prosthetic heart values are generally favoured only in older patients where re-operation is not likely to be required. The reason being that bioprosthetic valves have a more limited long-term durability. So why not always use mechanical valves? Their clotting risk is considerably higher and so they require higher intensity anticoagulant therapy - along with all of the attendant complications of that...