The heart has four functioning one-way valves; the aortic, mitral, pulmonary and tricuspid valves. These valves allow a measured amount of blood to flow from chamber to chamber in the heart and finally out to the aorta. When these valves become diseased and stop functioning, a cardiac surgeon can replace the valve. Typically it is either the aortic or mitral valve that is replaced. Replacement is done with either a completely mechanical valve or a bioprosthetic valve. A mechanical valve is made from carbon alloys and a bioprosthetic valve originates from living tissue.
Blood Clots
If a valve is replaced by a mechanical valve, the patient will require life-long anticoagulation or blood-thinning medication. This is because the mechanical valve has a tendency to attract platelets which adhere to the valve and cause obstruction. This complication can be significantly reduced with anticoagulation medicines such as warfarin or coumadin. Bioprosthetic valves do not have a significant rate of blood clot formation and therefore do not require a patient to be on life-long anticoagulation therapy.
Structural Failure
While the mechanical valve does require anticoagulation, it has a much greater life span than the bioprosthetic valve and typically does not suffer structural failure. A bioprosthetic valve has an expected life span of approximately 10 to 15 years depending on the age of the patient at the time of the replacement, according to The Society of Thoracic Surgeons. In the review article "Complications of Bioprosthetic Heart Valves," researchers state that structural failure in bioprosthetic valves occurs in 15 percent of aortic replacements and 36 percent of mitral replacements.
Infection
A foreign body in the circulatory system is at high risk for infection. Infective endocarditis or infection of the heart valve is a dreaded complication and carries a mortality risk of 80 percent if found in the early post-operative period, according to "Complications of Bioprosthetic Heart Valves." Infection of the heart valve can cause heart failure, clots, fevers and bacteria in the blood. Infective endocarditis can be treated with antibiotics, but frequently the valve needs to be removed. This is a life-threatening condition.
References
- "The Principles and Practice of Medicine"; John Stobo, MD, David Hellmann, MD, Paul Ladenson, MD, Brent Petty, MD & Thomas Traill, FRCP. 1996
- The Society of Thoracic Surgeons: Mitral Valve Replacement
- "The Washington Manual of Surgery, Fifth Edition"; Mary Klingensmith, MD, Li Chen, MD, Sean Glasgow, MD, Trudie Goers, MD, Spencer Melby, MD. 2008
- "Durability of Bioprosthetic Cardiac Valves"Gerard P Aurigemma, MD, William H Gaasch, MD. January 25, 2000.
