Sternotomy/Thoracotomy implantation [5]:
Ball mechanical valve – based on the blood flow direction the ball present in the contraption will move and change its direction. The valve will open when the aortic pressure increases causing the ball to be pushed away from the heart causing the blood to flow into the aorta. This in turn will cause pressure drop in the ventricles causing the ball to be sucked backwards. There is no central blood flow through this type of valve. In order for the blood to push the ball to allow blood flow, the heart has to apply greater pressure than in the normal conditions. There will be damage to the blood corpuscles which might even cause their death upon collision. Figure: Caged-ball valve. [5] Figure: (a) Hufnagel–Lucite valve, (b) Starr–Edwards, (c) Smeloff–Cutter,
(d) McGovern–Cronie, (e) DeBakey–Surgitool and (f)
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They are having the advantage of showing functioning like that of the normal human heart along with reduced blood clotting. Rejection rate of the graft is low because the tissue extracted has been treated to minimize the possibilities of surface antigen formation Table 1: classification of biological heart valve substitutes according to implantation procedure [8]
Allograft heart valves: [8] [10]
They are extracted from human heart donors and show high resistance to infections, geometric conformation compatibility, and low risk of anticoagulant complications.
Xenograft heart valves: [11]
They are collagen extracts from animal sources such as horse, pigs, cows, etc and can be derived from various locations such as the small intestine, external heart layers or the lower skin layers. They are treated with chemicals to increase durability and reduce rejection rate due to surface antigen formation. The main disadvantage is its wear ability which will lead to replacement requirement with time in like in the case of mechanical heart valves.
Auto graft