A heart transplant, or a cardiac transplant, is a surgical transplant procedure performed on patients with end-stage heart failure or severe coronary artery disease when other medical or surgical treatments have failed. As of 2016, the most common procedure is to take a functioning heart (with or without transplantation of a lung or lungs; a cadaveric donor cardiectomy) from a recently deceased organ donor (the cadaveric allograft), and implant it into the patient. The patient's own heart is either removed (the cardiectomy for the recipient) and replaced with the donor heart (orthotopic procedure) or, much less commonly, the recipient's diseased heart is left in place to support the donor heart (heterotopic, or "piggyback," transplant procedure). Approximately 3500 heart transplants are performed every year in the world, more than half of which occur in the US. Post-operation survival periods average 15 years. Heart transplantation is not considered to be a cure for heart disease, but a life-saving treatment intended to improve the quality of life for recipients.
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History
One of the first mentions of the possibility of heart transplantation was by American medical researcher Simon Flexner, who declared in a reading of his paper on "Tendencies in Pathology" in the University of Chicago in 1907 that it would be possible in the then-future for diseased human organs substitution for healthy ones by surgery -- including arteries, stomach, kidneys and heart.
Not having a human donor heart available, James D. Hardy of the University of Mississippi Medical Center transplanted the heart of a chimpanzee into the chest of a dying Boyd Rush in the early morning of Jan. 24, 1964. Hardy used a defibrillator to shock the heart to restart beating. This heart did beat in Rush's chest for 60 to 90 minutes (sources vary), and then Rush died without regaining consciousness. Although Hardy was a respected surgeon who had performed the world's first human-to-human lung transplant a year earlier, author Donald McRae states that Hardy could feel the "icy disdain" from fellow surgeons at the Sixth International Transplantation Conference several weeks after this attempt with the chimpanzee heart. Hardy had been inspired by the limited success of Keith Reemtsma at Tulane University in transplanting chimpanzee kidneys into human patients with kidney failure. The consent form Hardy asked Rush's step sister to sign did not include the possibility that a chimpanzee heart might be used, although Hardy stated that he did include this in verbal discussions.
Norman Shumway is widely regarded as the father of heart transplantation, although the world's first human-to-human heart transplant was performed by South African cardiac surgeon Christiaan Barnard utilizing the techniques developed and perfected by Shumway and Richard Lower. Barnard performed the first transplant on Louis Washkansky on December 3, 1967, at the Groote Schuur Hospital in Cape Town, South Africa. Adrian Kantrowitz performed the world's first pediatric heart transplant on December 6, 1967, at Maimonides Hospital in Brooklyn, New York, barely three days after Christiaan Barnard's pioneering operation. Since the 19-day-old infant died little more than six hours after receiving the heart, this operation was considered a failure. Norman Shumway performed the first adult heart transplant in the United States on January 6, 1968, at the Stanford University Hospital. A team led by Donald Ross performed the first heart transplant in the United Kingdom on May 3, 1968.
Worldwide, more than 100 transplants were performed by various doctors during 1968. Only a third of these patients lived longer than three months.
The next big breakthrough came in 1983 when cyclosporine entered widespread usage. This drug enabled much smaller amounts of corticosteroids to be used to prevent many cases of rejection (the "corticosteroid-sparing" effect of cyclosporine).
On 9 June 1984 "JP" Lovette IV of Denver became the world's first successful pediatric heart transplant. Columbia-Presbyterian Medical Center surgeons transplanted the heart of 4-year-old John Nathan Ford of Harlem into 4-year-old JP a day after the Harlem child died of injuries received in a fall from a fire escape at his home. JP was born with multiple heart defects. The transplant was done by a surgical team led by Dr. Eric A. Rose, director of cardiac transplantation at NewYork-Presbyterian Hospital. Drs. Keith Reemtsma and Fred Bowman also were members of the team for the six-hour operation.
Worldwide, about 3,500 heart transplants are performed annually. The vast majority of these are performed in the United States (2,000-2,300 annually). Cedars-Sinai Medical Center in Los Angeles, California, currently is the largest heart transplant center in the world, having performed 132 adult transplants in 2015 alone. About 800,000 people have NYHA Class IV heart failure symptoms indicating advanced heart failure. The great disparity between the number of patients needing transplants and the number of procedures being performed spurred research into the transplantation of non-human hearts into humans after 1993. Xenografts from other species and artificial hearts are two less successful alternatives to allografts.
The ability of medical teams to perform transplants continues to expand. For example, Sri Lanka's first heart transplant was successfully performed at the Kandy General Hospital on July 7, 2017.
During heart transplant, the vagus nerve is severed, thus removing parasympathetic influence over the myocardium. However, some limited return of sympathetic nerves has been demonstrated in humans.
Contraindications
Some patients are less suitable for a heart transplant, especially if they suffer from other circulatory conditions related to their heart condition. The following conditions in a patient increase the chances of complications;
Absolute contraindications:
- Advanced kidney, lung, or liver disease
- Active cancer if it is likely to impact the survival of the patient
- Life-threatening diseases unrelated to heart failure including acute infection or systemic disease such as systemic lupus erythematosus, sarcoidosis, or amyloidosis
- Vascular disease of the neck and leg arteries.
- High pulmonary vascular resistance - over 5 or 6 Wood units.
Relative contraindications:
- Insulin-dependent diabetes with severe organ dysfunction
- Recent thromboembolism such as stroke
- Severe obesity
- Age over 65 years (some variation between centers) - older patients are usually evaluated on an individual basis.
- Active substance abuse, such as alcohol, recreational drugs or tobacco smoking (which increases the chance of lung disease)
Patients who are in need of a heart transplant but do not qualify, may be candidates for an artificial heart or a left ventricular assist device (LVAD).
Complications
Post-operative complications include infection, sepsis, organ rejection, as well as the side-effects of the immunosuppressive medication. Since the transplanted heart originates from another organism, the recipient's immune system typically attempts to reject it. The risk of rejection never fully goes away, and the patient will be on immunosuppressive drugs for the rest of his or her life, but these may cause unwanted side effects, such as increased likelihood of infections or development of certain cancers. Recipients can acquire kidney disease from a heart transplant due to side effects of immunosuppressant medications. Many recent advances in reducing complications due to tissue rejection stem from mouse heart transplant procedures. Surgery death rate is 5-10% in 2011.
People who have had heart transplants are monitored in various ways to test for the development of rejection.
Prognosis
The prognosis for heart transplant patients following the orthotopic procedure has increased over the past 20 years, and as of June 5, 2009, the survival rates were:
- 1 year: 88.0% (males), 86.2% (females)
- 3 years: 79.3% (males), 77.2% (females)
- 5 years: 73.2% (males), 69.0% (females)
In 2007, researchers from the Johns Hopkins University School of Medicine discovered that "men receiving female hearts had a 15% increase in the risk of adjusted cumulative mortality" over five years compared to men receiving male hearts. Survival rates for women did not significantly differ based on male or female donors.
Source of the article : Wikipedia
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