Wednesday, August 16, 2017

HEART VALVE TRANSPLANTATION

The human heart has 4 chambers, which consist of 2 atria and 2 ventricles, one on each side. The upper chamber is the atrium and the lower one is the ventricle. Between each atrium and ventricle is a valve that keeps the blood flowing in the forward direction. Deoxygenated blood is brought to the right atrium, which then flows into the right ventricle, directed by the tricuspid valve. It then flows into the lungs via the pulmonary artery so that it can get oxygenated. The pulmonary valve controls the blood flow from the right ventricle into the lungs. Oxygen rich blood then flows to the left atrium and then into the left ventricle, directed by the mitral valve. The left ventricle, which is the largest and strongest of the four chambers, will then pump the blood into the aorta via the aortic valve to be distributed to the rest of the body.

Heart valves may need to be replaced if a child is born with a congenital defect or in diseased states such as infective endocarditis or mechanical abnormalities that might cause a valve to malfunction, sometimes seen after a heart attack. Options available to replace heart valves include artificial mechanical valves or those obtained either from an animal source such as the pig or from a human donor. Human heart valves can be obtained from hearts that are being replaced after a heart transplant or after a person agrees to becoming a tissue donor upon his death.

In adults, the most common heart valve operations are aortic and mitral valve replacements. A mechanical heart valve is made of synthetic but durable and long lasting materials and is expected to last a person’s lifetime. Persons receiving this kind of valve almost always will require blood thinning medications in order to avoid blood clots from developing and causing malfunction of the valve. These medications also prevent blood clots from getting dislodged and travelling to the brain causing a stroke or to the heart causing a heart attack. The disadvantage of taking a blood thinner is the increased risk of excessive bleeding.

Tissue valves are created from animal tissues (such as pig heart valves and cow valves made from the pericardium of a cow’s heart) and usually last 10-20 years. They do not require blood thinning medications long term. A human donor valve is the least common choice for heart valve replacement today and is also expected to last between 10 and 20 years without requiring blood thinners.

Donation of heart valves fall under the category of tissue donation. Most people are aware that organ donation can save upto 8 lives. Tissue donation can enhance or save over 50 individuals. Each year, approximately 30,000 tissue donors provide lifesaving tissue for transplantation. Over 1.5 million patients are helped with tissue donation every year in the US. Tissues commonly donated include corneas, heart valves, skin, bone, blood vessels and tendons.

Age criteria for heart valve recovery include donors being between newborns to 60 years of age. Valves can be recovered within 15 hours if the body is not refrigerated or within 24 hours if the body is refrigerated within 12 hours of death. After removal, recovery professionals carefully inspect the valves for any abnormality before processing and storage. Processed and packaged heart valves are stored in minus 100 degrees Centigrade or cooler and have an expiration date of 5 years.

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