Mechanical and Biological Heart Valves
Writer: Prof. Dr. Yavuz Besogul
For patients with significant valve disease, surgical treatment options include valve repair or replacement. The choice between repair and replacement is affected by a number of factors, including age, type of valve disease, and other medical conditions. When valve replacement is performed, there are options for mechanical or tissue heart valves. These two classes of valves bring different characteristics and each has advantages and disadvantages.
Mechanical heart valves
Mechanical heart valves are made of materials such as titanium and carbon. They usually consist of a metal ring surrounded by two leaflets and a loop of knitted fabric that is sewn to the heart in place of the original valve. Several different models are available for aortic and mitral replacement surgeries. The main advantage of mechanical valves is that they are very durable. However, these valves provide a surface on which blood clots can easily form. As a result, anyone implanted with a mechanical valve must take blood-thinning medication for life to prevent the development of blood clots that can cause a heart attack or stroke.
Biological or bioprosthetic valves
Tissue valves, also known as biological or bioprosthetic valves, are composed of animal or human tissue. Valves are derived from animal tissue, such as porcine (pig), bovine (cow), and equine (horse) models, and are secured with a protective solution that can then be mounted on a flexible frame to aid deployment during surgery. As with mechanical valves, the base of a tissue valve is usually surrounded by a ring of knitted fabric sewn to the heart.
In addition to animal-derived valves, a human tissue valve from a donor human heart, known as an allograft or homograft, can also be used as a replacement valve. Tissue valves can be used in open-heart surgery or a minimally invasive aortic operation known as transcatheter aortic valve implantation (TAVI). Advantages of tissue valves over mechanical valves include avoiding lifelong warfarin therapy to prevent the development of blood clots. One disadvantage is their relatively poor durability compared to mechanical valves, with many requiring rework within 10 to 20 years.