出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/12/12 19:44:33」(JST)
An artificial heart is a device that replaces the heart. Artificial hearts are typically used to bridge the time to heart transplantation, or to permanently replace the heart in case heart transplantation is impossible. Although other similar inventions preceded it going back to the late 1940s, the first artificial heart to be successfully implanted in a human was the Jarvik-7, designed by Robert Jarvik and implemented in 1982.
An artificial heart is distinct from a ventricular assist device designed to support a failing heart. It is also distinct from a cardiopulmonary bypass machine, which is an external device used to provide the functions of both the heart and lungs and are only used for a few hours at a time, most commonly during cardiac surgery.
A synthetic replacement for the heart remains one of the long-sought holy grails of modern medicine. The obvious benefit of a functional artificial heart would be to lower the need for heart transplants, because the demand for organs always greatly exceeds supply.
Although the heart is conceptually a pump, it embodies subtleties that defy straightforward emulation with synthetic materials and power supplies. Consequences of these issues include severe foreign-body rejection and external batteries that limit patient mobility. These complications limited the lifespan of early human recipients to hours or days.
A heart-lung machine was used in 1953 during a successful open heart surgery. Dr. John Heysham Gibbon, the inventor of the machine, performed the operation and developed the heart-lung substitute himself.
Although Jarvik created the idea and rough draft for the artificial heart, his models were not created of a material that the human body would accept. Dayton, Ohio's Ival O. Salyer, along with various colleagues, developed a polymer material that the human body would not necessarily reject.
On July 3, 1952, 41-year-old Henry Opitek, suffering from shortness of breath, made medical history at Harper University Hospital at Wayne State University in Michigan. The Dodrill-GMR heart machine, considered to be the first operational mechanical heart, was successfully used while performing heart surgery.[1][2]
Dr. Forest Dewey Dodrill, working closely with Dr. Matthew Dudley, used the machine in 1952 to bypass Henry Opitek's left ventricle for 50 minutes while he opened the patient's left atrium and worked to repair the mitral valve. In Dr. Dodrill's post-operative report, he notes, "To our knowledge, this is the first instance of survival of a patient when a mechanical heart mechanism was used to take over the complete body function of maintaining the blood supply of the body while the heart was open and operated on."[3]
The scientific interest for the development of a solution for heart disease developed in different research groups worldwide.
In 1949, a precursor to the modern artificial heart pump was built by doctors William Sewell and William Glenn of the Yale School of Medicine using an Erector Set, assorted odds and ends, and dime-store toys. The external pump successfully bypassed the heart of a dog for more than an hour.[4]
American ventriloquist and inventor Paul Winchell invented an artificial heart with the assistance of Dr. Henry Heimlich (the inventor of the Heimlich Maneuver) and held the first patent for such a device. The University of Utah developed a similar apparatus around the same time, but when they tried to patent it, Winchell's heart was cited as prior art. The university requested that Winchell donate the heart to the University of Utah, which he did. There is some debate as to how much of Winchell's design Dr. Robert Jarvik used in creating Jarvik's artificial heart. Dr. Heimlich states, "I saw the heart, I saw the patent and I saw the letters. The basic principle used in Winchell's heart and Jarvik's heart is exactly the same." Jarvik denies that any of Winchell's design elements were incorporated into the device he fabricated for humans which was successfully implanted into Barney Clark in 1982.
On December 12, 1957, Dr. Willem Johan Kolff, the world's most prolific inventor of artificial organs, implanted an artificial heart into a dog at Cleveland Clinic. The dog lived for 90 minutes.
In 1958, Domingo Liotta initiated the studies of TAH replacement at Lyon, France, and in 1959–60 at the National University of Córdoba, Argentina. He presented his work at the meeting of the American Society for Artificial Internal Organs held in Atlantic City in March 1961. At that meeting, Dr. Liotta described the implantation of three types of orthotopic (inside the pericardial sac) TAHs in dogs, each of which used a different source of external energy: an implantable electric motor, an implantable rotating pump with an external electric motor, and a pneumatic pump.[5][6]
In 1964, the National Institutes of Health started the Artificial Heart Program, with the goal of putting a man-made organ into a human by the end of the decade.[7]
In February 1966, Dr. Adrian Kantrowitz rose to international prominence when he performed the world's first permanent implantation of a partial mechanical heart (left ventricular assist device) at Maimonides Medical Center.[8]
In 1967, Dr. Kolff left Cleveland Clinic to start the Division of Artificial Organs at the University of Utah and pursue his work on the artificial heart.
Over the years, more than 200 physicians, engineers, students and faculty developed, tested and improved Dr. Kolff's artificial heart. To help manage his many endeavors, Dr. Kolff assigned project managers. Each project was named after its manager. Graduate student Robert Jarvik was the project manager for the artificial heart, which was subsequently renamed the Jarvik 7.
In 1981, Dr. William DeVries submitted a request to the FDA to implant the Jarvik 7 into a human being. On December 2, 1982, Dr. Kolff implanted the Jarvik 7 artificial heart into Barney Clark, a dentist from Seattle who was suffering from severe congestive heart failure. While Clark lived for 112 days tethered to an external pneumatic compressor, a device weighing some 400 pounds (180 kg), during that time he suffered prolonged periods of confusion and a number of instances of bleeding, and asked several times to be allowed to die.[9]
On April 4, 1969, Domingo Liotta and Denton A. Cooley replaced a dying man's heart with a mechanical heart inside the chest at The Texas Heart Institute in Houston as a bridge for a transplant. The patient woke up and recovered well. After 64 hours, the pneumatic-powered artificial heart was removed and replaced by a donor heart. However thirty-two hours after transplantation, the patient died of what was later proved to be an acute pulmonary infection, extended to both lungs, caused by fungi, most likely caused by an immunosuppressive drug complication.[10]
The original prototype of Liotta-Cooley artificial heart used in this historic operation is prominently displayed in the Smithsonian Institution's National Museum of American History "Treasures of American History" exhibit in Washington, D.C.[11]
The eighty-fifth clinical use of an artificial heart designed for permanent implantation rather than a bridge to transplant occurred in 1982 at the University of Utah. Artificial kidney pioneer Dr. Willem Johan Kolff started the Utah artificial organs program in 1967.[12] There, physician-engineer Dr. Clifford Kwan-Gett invented two components of an integrated pneumatic artificial heart system: a ventricle with hemispherical diaphragms that did not crush red blood cells (a problem with previous artificial hearts) and an external heart driver that inherently regulated blood flow without needing complex control systems.[13] Independently, ventriloquist Paul Winchell designed and patented a similarly shaped ventricle and donated the patent to the Utah program.[14] Throughout the 1970s and early 1980s, veterinarian Dr. Donald Olsen led a series of calf experiments that refined the artificial heart and its surgical care. During that time, as a student at the University of Utah, Dr. Robert Jarvik combined several modifications: an ovoid shape to fit inside the human chest, a more blood-compatible polyurethane developed by biomedical engineer Dr. Donald Lyman, and a fabrication method by Kwan-Gett that made the inside of the ventricles smooth and seamless to reduce dangerous stroke-causing blood clots.[15] On December 2, 1982, Dr. William DeVries implanted the artificial heart into retired dentist Dr. Barney Bailey Clark (born January 21, 1921), who survived 112 days with the device, dying on March 23, 1983. Bill Schroeder became the second recipient and lived for a record 620 days.
Contrary to popular belief and erroneous articles in several periodicals, the Jarvik heart was not banned for permanent use. Today, the modern version of the Jarvik 7 is known as the SynCardia temporary CardioWest Total Artificial Heart. It has been implanted in more than 800 people as a bridge to transplantation.
In the mid-1980s, artificial hearts were powered by dishwasher-sized pneumatic power sources whose lineage went back to Alpha-Laval milking machines. Moreover, two sizable catheters had to cross the body wall to carry the pneumatic pulses to the implanted heart, greatly increasing the risk of infection. To speed development of a new generation of technologies, the National Heart, Lung, and Blood Institute opened a competition for implantable electrically powered artificial hearts. Three groups received funding: Cleveland Clinic in Cleveland, Ohio; the College of Medicine of Pennsylvania State University (Penn State Hershey Medical Center) in Hershey, Pennsylvania; and AbioMed, Inc. of Danvers, Massachusetts. Despite considerable progress, the Cleveland program was discontinued after the first five years.
Polymeric trileaflet valves ensure unidirectional blood flow with a low pressure gradient and good longevity. State-of-the-art transcutaneous energy transfer eliminates the need for electric wires crossing the chest wall.
On July 19, 1963, E. Stanley Crawford and Domingo Liotta implanted the first clinical Left Ventricular Assist Device (LVAD) at The Methodist Hospital in Houston, Texas, in a patient who had a cardiac arrest after surgery. The patient survived for four days under mechanical support but did not recover from the complications of the cardiac arrest; finally, the pump was discontinued, and the patient died.
On April 21, 1966, Michael DeBakey and Liotta implanted the first clinical LVAD in a paracorporeal position (where the external pump rests at the side of the patient) at The Methodist Hospital in Houston, in a patient experiencing cardiogenic shock after heart surgery. The patient developed neurological and pulmonary complications and died after few days of LVAD mechanical support. In October 1966, DeBakey and Liotta implanted the paracorporeal Liotta-DeBakey LVAD in a new patient who recovered well and was discharged from the hospital after 10 days of mechanical support, thus constituting the first successful use of an LVAD for postcardiotomy shock.
In June 1996, a 46-year-old Taiwanese American Mr. Yao ST received the world's first total artificial heart implantation done by Dr. Jeng Wei at Cheng-Hsin General Hospital[16] in the Republic of China (Taiwan). This technologically advanced pneumatic Phoenix-7 Total Artificial Heart was manufactured by a Taiwanese dentist Kelvin K. Cheng, a Chinese physican T. M. Kao and colleagues at the Taiwan TAH Research Center in Tainan, Republic of China (Taiwan). With this experimental artificial heart, the patient's BP was maintained at 90-100/40-55 mmHg and cardiac output at 4.2-5.8 L/min. After 15 days of bridging, Mr. Yao received combined heart and kidney transplantation. As of March 2013[update], he is still very well and is currently living in San Francisco, USA.[citation needed] Mr. Yao ST is the world first successful combined heart and kidney transplantation patient after bridging with total artificial heart.[17]
The first AbioCor to be surgically implanted in a patient was on July 3, 2001.[18] The AbioCor is made of titanium and plastic with a weight of two pounds, and its internal battery can be recharged with a transduction device that sends power through the skin.[18] The internal battery lasts for a half hour, and a wearable external battery pack lasts for four hours.[19] The FDA announced on September 5, 2006, that the AbioCor could be implanted for humanitarian uses after the device had been tested on 15 patients.[20] It is intended for critically ill patients who can not receive a heart transplant.[20] Some limitations of the current AbioCor are that its size makes it suitable for only about 50% of the male population, and its useful life is only 1–2 years.[21]
By combining its valved ventricles with the control technology and roller screw developed at Penn State, AbioMed has designed a smaller, more stable heart, the AbioCor II. This pump, which should be implantable in most men and 50% of women with a life span of up to five years,[21] had animal trials in 2005, and the company hoped to get FDA approval for human use in 2008.[22]
In August 2006, an artificial heart was implanted into a 15-year-old girl at the Stollery Children's Hospital in Edmonton, Alberta. It was intended to act as a temporary fixture until a donor heart could be found. Instead, the artificial heart (called a Berlin Heart) allowed for natural processes to occur and her heart healed on its own. After 146 days, the Berlin Heart was removed, and the girl's heart was able to function properly on its own.[23] On December 16, 2011 the Berlin Heart gained U.S. FDA approval. The device has since been successfully implanted in several children including a 4-year-old Honduran girl at Children's Hospital Boston.[24]
In 2012, a study published in the New England Journal of Medicine compared the Berlin Heart to extracorporeal membrane oxygenation (ECMO) and concluded that "a ventricular assist device available in several sizes for use in children as a bridge to heart transplantation [such as the Berlin Heart] was associated with a significantly higher rate of survival as compared with ECMO."[25] The study's primary author, Dr. Charles D. Fraser, Jr., surgeon in chief at Texas Children's Hospital, explained: “With the Berlin Heart, we have a more effective therapy to offer patients earlier in the management of their heart failure. When we sit with parents, we have real data to offer so they can make an informed decision. This is a giant step forward.” [26]
On October 27, 2008, French professor and leading heart transplant specialist Alain F. Carpentier announced that a fully implantable artificial heart will be ready for clinical trial by 2011 and for alternative transplant in 2013. It was developed and will be manufactured by him, biomedical firm CARMAT SA, and venture capital firm Truffle Capital. The prototype uses embedded electronic sensors and is made from chemically treated animal tissues, called "biomaterials", or a "pseudo-skin" of biosynthetic, microporous materials.[27] According to an interview of the professor Alain Carpentier in Paris (2011), a number of leading cardiac clinics already conducted successful partial replacement of the organic components of the artificial heart, for example, replacing valves, large vessels, atria, ventricles. In addition to cardio-surgery, there is the medico-psychological aspect of an artificial heart. A quarter of patients in the postoperative period after prosthetic valvular surgery developed specific psychopathological symptoms, which later received the name Skumin syndrome in 1978. It is possible that a similar problem will be discovered when conducting large-scale operations to implant an artificial heart.[28]
Another U.S. team has a prototype called the 2005 MagScrew Total Artificial Heart. Teams in Japan and South Korea are also racing to produce similar projects.[29][30][31]
In August 2010, 50-year-old Angelo Tigano of Fairfield, New South Wales, Australia, had his failing heart removed in a five-hour operation and it was replaced with the SynCardia temporary Total Artificial Heart by surgeon Dr Phillip Spratt, head of the heart transplant unit at St Vincent's Hospital, Sydney.[32]
On 9 June 2011, 40-year-old Matthew Green was implanted with the SynCardia temporary Total Artificial heart in a seven-hour operation at Papworth Hospital. He was the first Briton to leave a hospital supported by an artificial Heart on 2 August 2011.[33]
On 12 March 2011, an experimental artificial heart was implanted in 55-year-old Craig Lewis at The Texas Heart Institute in Houston by Drs. O. H. Frazier and William Cohn. The device is a combination of two modified HeartMate II pumps that is currently undergoing bovine trials.[34]
A centrifugal pump[35][36] or an axial-flow pump[37][38] can be used as an artificial heart, resulting in the patient being alive without a pulse.
Imachi et al. described a centrifugal artificial heart which alternately pumps the pulmonary circulation and the systemic circulation, causing a pulse.[39]
An operation inserting an artificial heart was described by Science Fiction writer Homer Eon Flint in his 1919 novel The Devolutionist and the Emancipatrix.
Captain Jean-Luc Picard has an artificial heart in Star Trek: The Next Generation, having sustained a stab wound to his heart as a young man.
Tony Stark, from the original comic Iron Man, took a sever injury to his heart. In order to prevent death, Stark was equipped with armor that would keep his heart beating. His heart would only beat if he wore that armor. Eventually, Stark would have to undergo transplant surgery, giving him an artificial heart, so that he would no longer have to wear the chest plate.
In the popular Tuesday evening BBC drama Holby City, Professor Hope, a leading cardiothoracic surgeon, has developed an artificial heart called the Herzig. At the time of writing the article, the Herzig-4 (the most recent version) has been inserted in a young man with heart failure. The success of this artificial transplant (as of episode 3, series 16 from 29/10/13) has yet to be confirmed.
Patients who have some remaining heart function but who can no longer live normally may be candidates for ventricular assist devices (VAD), which do not replace the human heart but complement it by taking up much of the function.
The first Left Ventricular Assist Device (LVAD) system was created by Domingo Liotta at Baylor College of Medicine in Houston in 1962.[40]
Another VAD, the Kantrowitz CardioVad, designed by Adrian Kantrowitz boosts the native heart by taking up over 50% of its function.[41] Additionally, the VAD can help patients on the wait list for a heart transplant. In a young person, this device could delay the need for a transplant by 10–15 years, or even allow the heart to recover, in which case the VAD can be removed.[41] The artificial heart is powered by a battery that needs to be changed several times while still working.
The first heart assist device was approved by the FDA in 1994, and two more received approval in 1998.[42] While the original assist devices emulated the pulsating heart, newer versions, such as the Heartmate II,[43] developed by The Texas Heart Institute of Houston, provide continuous flow. These pumps (which may be centrifugal or axial flow) are smaller and potentially more durable and last longer than the current generation of total heart replacement pumps. Another major advantage of a VAD is that the patient keeps the natural heart, which may still function for temporary back-up support if the mechanical pump were to stop. This may provide enough support to keep the patient alive until a solution to the problem is implemented.
Several continuous-flow ventricular assist devices have been approved for use in the European Union, and, as of August 2007, were undergoing clinical trials for FDA approval.
Suffering from end-stage heart failure, former Vice President Dick Cheney underwent a procedure in July 2010 to have a VAD implanted at INOVA Fairfax Hospital, in Fairfax Virginia. In 2012, he received a heart transplant at age 71 after 20 months on a waiting list.
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