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Heart Transplants

Lewis

Lewis

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This is in 2 posts
A heart transplant, or a cardiac transplantation, is a surgical transplant procedure performed on patients with end-stage heart failure or severe coronary artery disease. The most common procedure is to take a working heart from a recently deceased organ donor (cadaveric allograft) and implant it into the patient. The patient's own heart may either be removed (orthotopic procedure) or, less commonly, left in to support the donor heart (heterotopic procedure); both are controversial solutions to one of the most enduring human ailments. Post-operation survival periods now average 15 years.[1]
The world's first human heart transplant was performed by Christiaan Barnard on a man called Louis Washkansky in 1967.[2] The first successful human heart transplant in the United States was performed at Maimonides Medical Center.[3] Worldwide there are 3,500 heart transplants performed every year; about 800,000 people have a Class IV heart defect and need a new organ.[4] This disparity has spurred considerable research into the use of non-human hearts since 1993. It is now possible to take a heart from another species (xenograft), or implant a man-made artificial one, although the outcome of these two procedures has been less successful in comparison to the far more commonly performed allografts. Engineers want to fix the remaining problems with the manufactured options in the next 15 years.[1]

Contraindications

Some patients are less suitable for a heart transplant, especially if they suffer from other circulatory conditions unrelated to the heart. The following conditions in a patient would increase the chances of complications occurring during the operation:

Procedures

Pre-operative

A typical heart transplantation begins with a suitable donor heart being located from a recently deceased or brain dead donor, also called a beating heart cadaver. The transplant patient is contacted by a nurse coordinator and instructed to attend the hospital in order to be evaluated for the operation and given pre-surgical medication. At the same time, the heart is removed from the donor and inspected by a team of surgeons to see if it is in a suitable condition to be transplanted. Occasionally it will be deemed unsuitable. This can often be a very distressing experience for an already emotionally unstable patient, and they will usually require emotional support before being sent home. The patient must also undergo many emotional, psychological, and physical tests to make sure that they are in good mental health and will make good use of their new heart. The patient is also given immunosuppressant medication so that their immune system will not reject the new heart.
Operative


Schematic of a transplanted heart with native lungs and the great vessels.


Once the donor heart has passed its inspection, the patient is taken into the operating room and given a general anesthetic. Either an orthotopic or a heterotopic procedure is followed, depending on the condition of the patient and the donor heart.
Orthotopic procedure

The orthotopic procedure begins with the surgeons performing a median sternotomy to expose the mediastinum. The pericardium is opened, the great vessels are dissected and the patient is attached to cardiopulmonary bypass. The failing heart is removed by transecting the great vessels and a portion of the left atrium. The pulmonary veins are not transected; rather a circular portion of the left atrium containing the pulmonary veins is left in place. The donor heart is trimmed to fit onto the patient's remaining left atrium and the great vessels are sutured in place. The new heart is restarted, the patient is weaned from cardiopulmonary bypass and the chest cavity is closed.
 
Heterotopic procedure

In the heterotopic procedure, the patient's own heart is not removed before implanting the donor heart. The new heart is positioned so that the chambers and blood vessels of both hearts can be connected to form what is effectively a 'double heart'. The procedure can give the patients original heart a chance to recover, and if the donor's heart happens to fail (e.g. through rejection), it may be removed, allowing the patient's original heart to start working again. Heterotopic procedures are only used in cases where the donor heart is not strong enough to function by itself (due to either the patient's body being considerably larger than the donor's, the donor having a weak heart, or the patient suffering from pulmonary hypertension).
Post-operative

The patient is taken into the ICU to recover. When they wake up, they will be transferred to a special recovery unit in order to be rehabilitated. How long they remain in hospital post-transplant depends on the patient's general health, how well the new heart is working, and their ability to look after their new heart. Doctors typically like the new recipients to leave hospitals soon after surgery because of the risk of infection in a hospital (typically 1 – 2 weeks without any complications). Once the patient is released, they will have to return to the hospital for regular check-ups and rehabilitation sessions. They may also require emotional support. The number of visits to the hospital will decrease over time, as the patient adjusts to their transplant. The patient will have to remain on immunosuppressant medication to avoid the possibility of rejection. Since the vagus nerve is severed during the operation, the new heart will beat at around 100 beats per minute unless nerve regrowth occurs.
The patient will be monitored to detect rejection of the heart by the body. This surveillance can be performed via frequent biopsy or a gene expression blood test known as AlloMap Molecular Expression Testing. Typically, biopsy is performed immediately post transplant and then AlloMap blood testing is performed once the patient is stable. The transition from biopsy to AlloMap could occur as soon as 55 days post transplant.
'Living organ' transplant

Doctors made medical history in February 2006, at Bad Oeynhausen Clinic for Thorax- and Cardiovascular Surgery, Germany, when they successfully transplanted a 'beating heart' into a patient.[5] Normally a donor's heart is injected with potassium chloride in order to stop it beating, before being removed from the donor's body and packed in ice in order to preserve it. The ice can usually keep the heart fresh for a maximum of four[6] to six hours with proper preservation, depending on its starting condition. Rather than cooling the heart, this new procedure involves keeping it at body temperature and connecting it to a special machine called an Organ Care System that allows it to continue beating with warm, oxygenated blood flowing through it. This can maintain the heart in a suitable condition for much longer than the traditional method.
Complications

Post-operative complications include infection, sepsis, organ rejection, as well as the side-effects of the immunosupressive medication. Since the transplanted heart originates from another organism, the recipient's immune system may attempt to reject it. Immunosupressive drugs reduce that risk, but may have some unwanted side effects, such as increased likelihood of infections or nephrotoxic effects. Many recent advances in reducing complications due to tissue rejection stem from mouse heart transplant procedures.[7]
Prognosis

The prognosis for heart transplant patients following the orthotopic procedure has greatly increased over the past 20 years, and as of June 5, 2009, the survival rates were as follows.[8]

  • 1 year: 88.0% (males), 86.2% (females)
  • 3 years: 79.3% (males), 77.2% (females)
  • 5 years: 73.1% (males), 69.0% (females)
In a November 2008 study conducted on behalf of the U.S. federal government by Dr. Eric Weiss of the Johns Hopkins University School of Medicine, it was discovered that heart transplants — all other factors being accounted for — work better in same-sex transplants (male to male, female to female). However, due to the present acute shortage in donor hearts, this may not always be feasible.
As of August 2009, Tony Huesman was the world's longest living heart transplant recipient, having survived for 31 years with a transplanted heart. Huesman received a heart in 1978 at the age of 20 after viral pneumonia severely weakened his heart. Huesman died on August 10, 2009 of cancer.[9] The operation was performed at Stanford University under American heart transplant pioneer Dr. Norman Shumway.[10]
Another noted heart transplant recipient, Kelly Perkins, climbs mountains around the world to promote positive awareness of organ donation. Perkins is the first heart transplant recipient to climb to the peaks of Mt. Fuji, Mt. Kilimanjaro, the Matterhorn, Mt. Whitney, and Cajon de Arenales in Argentina in 2007, 12 years after her transplant surgery. Dwight Kroening is yet another noted recipient promoting positive awareness for organ donation. Twenty-two years after his heart transplant, he is the first to finish an Ironman competition.[11]
Fiona Coote was the second Australian to receive a heart transplant in 1984 (at age 14) and the youngest Australian. At 24 years since her transplant she is also a long-term survivor and is involved in publicity and charity work for the Red Cross, and promoting organ donation in Australia.
 
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