|March 26, 2016|
An artificial heart is a mechanical device that replaces the heart. Artificial hearts are typically used in order to bridge the time to heart transplantation, or to permanently replace the heart in case transplantation is impossible.
An artificial heart is also distinct from a cardiopulmonary bypass machine (CPB), which is an external device used to provide the functions of both the heart and lungs. CPBs are only used for a few hours at a time, most commonly during heart surgery.
The SynCardia temporary Total Artificial Heart was the first FDA -approved Total Artificial Heart. It received FDA approval on October 15, 2004, following a 10-year clinical study.
Originally designed as a permanent replacement heart, it is currently approved as a bridge to human heart transplant for patients dying because both sides of their hearts are failing (irreversible end stage biventricular failure).
During the 10-year study, 79% of patients receiving the Total Artificial Heart survived to transplant ( New England Journal of Medicine 2004; 351: 859-867). This is the highest bridge-to-transplant rate for any heart device in the world. (See FDA Summary of Safety and Effectiveness )
AbioCor Replacement Heart
Unlike the CardioWest TAH, the AbioCor Replacement Heart by Abiomed is fully implantable, meaning that no wires or tubes penetrate the skin, and, therefore, there is less risk of infection.
The AbioCor is approved for use in severe biventricular end-stage heart disease patients who are not eligible for heart transplant and have no other viable treatment options. To date, 15 patients have been implanted with the AbioCor, with one patient living for 512 days with the AbioCor.
The AbioCor received FDA approval under a Humanitarian Device Exemption (HDE) on September 5, 2006. The first implant of the AbioCor since receiving FDA approval in 2006 took place on June 24, 2009, at Robert Wood Johnson University Hospital, New Jersey. This patient later died on August 23, 2009: (See FDA Summary of Safety and Probable Benefit .)
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 simple (basically a muscle that functions as 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.
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.
Dr. Forest Dewey Dodrill 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."
The scientific interest for the development of a solution for heart disease developed in different research groups worldwide.
Early designs of total artificial hearts
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.
On December 12, 1957, Dr. Willem 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 Cordoba, 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.
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.
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.
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 the artificial heart, a device weighing some , 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.
On February 11, 2009, Dr. Kolff died at the age of 97 in Philadelphia, Pennsylvania.
First clinical implantation of a total artificial heart
On the morning of 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. Replacing the artificial heart proved to be a bad decision, 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. If they had left the artificial heart in place, the patient may have lived longer.
The original prototype of Liotta-Cooley artificial heart used in this historic operation is prominently displayed in The Smithsonian Museum "Treasures of American History" exhibit in Washington, D.C.
First clinical applications of a permanent pneumatic total artificial heart
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. 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. Independently, ventriloquist Paul Winchell designed and patented a similarly shaped ventricle and donated the patent to the Utah program. 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. 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.
The first AbioCor to be surgically implanted in a patient was on July 3, 2001.
First clinical application of an intrathoracic pump
On the evening of 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.
First clinical application of a paracorporeal pump
On the afternoon of 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 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.
With increased understanding of the heart and continuing improvements in prosthetics engineering, computer science, electronics, battery technology, and fuel cells, a practical artificial heart may become a reality.
Total artificial heart
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, and venture capital firm Truffle. The prototype uses electronic sensors and is made from chemically treated animal tissues, called "biomaterials", or a "pseudo-skin" of biosynthetic, microporous materials. Another US team with a prototype called 2005 MagScrew Total Artificial Heart, including Japan and South Korea researchers are racing to produce similar projects.
In August 2010, 50-year-old Fairfield man Angelo Tigano had his failing heart removed in a five-hour operation and it was replaced with a Total Artificial Heart by surgeon Dr Phillip Spratt, head of the heart transplant unit at St Vincent's Hospital in Sydney. This was the first case of an artificial heart being implanted into a living human in the southern hemisphere.
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.
Another VAD, the Kantrowitz CardioVad, designed by Adrian Kantrowitz, MD, boosts the native heart by taking up over 50% of its function. 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.
The first heart assist device was approved by the FDA in 1994, and two more received approval in 1998.
While the original assist devices emulated the pulsating heart, newer versions, such as the Heartmate II, developed by the Texas Heart Institute of Houston, Texas, 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 can keep the natural heart, which can receive signals from the brain to increase and decrease the heart rate as needed. With the completely mechanical systems, the heart rate is fixed.
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.
GNU Free Documentation License. It uses material from the Wikipedia article "artificial heart".
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