A big step towards carbon based bio mechanization - artificial heart
2024-10-08
In the medical drama "Everything About Dr. Tang", Tang Jiayu, a smart, resolute, and somewhat "axial" returnee cardiac surgeon, gained the attention of the audience, especially her leading research and development of the "fully magnetic levitation artificial heart". Today, let me explain to you what this' fully magnetic levitation artificial heart 'is all about. Firstly, it should be clarified that the English name for a fully artificial heart is Total Artificial Heart (TAH), which is a mechanical heart that can fully replace the pumping function of the left and right hearts. The artificial heart mentioned in the TV series should refer to ventricular assist devices (VADs), which are used to replace the pumping of blood by the heart's ventricles. Heart failure is a major challenge in global medicine. After the development of heart failure to the end-stage, the treatment and management methods are extremely limited. Heart transplantation is widely recognized as an effective treatment, but due to the limited number of donor hearts, only a few hundred heart transplants can be performed annually in China. Compared to the hundreds of thousands of patients who may benefit from heart transplantation, the role of heart transplantation is insignificant. Although research has shown that the heart also has some other functions, the most important one is its role as a blood pump. If its mechanical pumping function is replaced, it can save the lives of patients with severe heart failure. The development history of artificial hearts is actually quite long, and the concept can even be traced back to 1812. In 1812, Julien Jean Cesar LeGallois proposed the concept of "mechanical circulation assistance". Over a hundred years later, in 1937, Soviet medical scientist Dr. Vladimir P. Demikhov developed the Total Artificial Heart (TAH) device. In 1953, American surgeon Gibbon developed the first extracorporeal circulation machine for human cardiac surgery and became the father of extracorporeal circulation. He shared his device with the Mayo Clinic, and they continued to promote the device, naming it the "Mayo Gibbon extracorporeal circulation machine," which saved hundreds of patients. In theory, an artificial heart is a miniaturized, less damaging, and long-lasting blood pump device. In the 1950s, Dr. Kolff of the United States developed a fully artificial heart at Cleveland Medical Center and applied it to animal experiments. The first person to obtain a patent for an artificial heart was American Paul Winchell (1963). Years later, Winchell transferred the patent rights to Kolf. In 1967, Korf left the Cleveland Clinic and founded the Department of Artificial Organs at the University of Utah, continuing to work on artificial hearts. On April 4, 1969, Domingo Liotta and Denton A. Cooley replaced the heart of a dying person with a mechanical heart in the chest cavity at the Texas Heart Center in Houston, marking the world's first clinical implantation of a fully artificial heart. At Pennsylvania State University, Dr. William Pierce developed a pneumatic heart assist device. The device eventually became the Thoratec Pneumatic VAD, the first VAD approved by the US Food and Drug Administration (FDA) for transplant transition. The first generation VAD device was gas driven and produced pulsatile blood flow similar to that of the heart. This technology has further developed into HeartMate I, which has been used as a pre transplant transition period for over 25 years. In 1971, three important figures joined Dr. Kolf's team: veterinarian Don Olsen (leading animal experiments), medical engineer Robert Jarvik (designing various artificial hearts), and surgeon Dr. William DeVries (leading the transition from animal implantation to human experiments). In 1982, the Kolf team first used an artificial heart as a bridge for permanent implantation rather than transplantation. The name of this artificial heart is Jarvik 7. Today, the modern version of Jarvik7 is called SynCardia Temporary Fully Artificial Heart. Used as a bridge for transplantation. 6% of all total artificial heart (TAH) transplants. The development of SynCardia also experienced setbacks. In 1990, the FDA suspended the TAH research project due to violations of FDA guidelines and regulations. In order to save TAH technology, UMC and the Research Foundation established a new company and joint venture in 1991. Transferring Jarvik7 technology to UMC, and subsequently renaming Jarvik7 to CardioWest? Fully artificial heart. The research time of TAH is quite long. Until October 15, 2004, the CardioWest fully artificial heart received FDA approval, becoming the first TAH to be approved for marketing. Although a fully artificial heart is a remarkable achievement, it is also very expensive. After SynCardia, AbioCor TAH emerged. This is the first 'self-sufficient internal artificial heart'. Researchers have been studying and testing this device for 30 years. The clinical trial began in 2001, the same year the device was implanted into the human body. AbioCor continued to receive FDA approval in 2006. Compared with TAH, VAD has a relatively simple structure, and most heart failure patients mainly suffer from ventricular dysfunction. Therefore, VAD can meet the needs of most heart failure (HF) patients. With the development of modern science and technology, VAD has gradually become an important means of treating end-stage heart failure. The clinical application of VAD in developed countries has made rapid progress and has developed into an effective treatment for late stage refractory heart failure that is widely accepted. According to statistics, the cumulative number of VAD implants worldwide has exceeded 60000 cases. The second generation VAD adopts a non pulsatile continuous blood flow mode. The driving mode of this pump belongs to the mechanical bearing type. The reason for developing a new type of VAD is that research on the first generation VAD, called REMOCH, has found many shortcomings. After the REMOCH test, there was a fundamental change in LVAD design. Blood is propelled through a rotor, and the flow is continuous, unlike the pulsations in the native heart. These devices are different from the early HeartMate I and require systemic anticoagulation. This type of VAD is currently the most commonly used VAD. As of 2020, over 27000 heart failure patients have received HeartMate II LVAD. Many people have already passed the 5-year treatment milestone, and some have been implanted with HeartMate II for over 10 years. But these achievements did not stop the researchers. The suspension system used in the third-generation rotary blood pump suspends the rotating impeller in the blood field without any mechanical contact. The suspended artificial heart has no bearing contact points, which can reduce damage to the blood. The magnetic levitation and/or fluid dynamic suspension of the impeller are the main advances of the third-generation pump. The blood film suspended by fluid dynamics has high shear stress, which can lead to blood damage. Magnetic levitation refers to the situation where the impeller of an artificial heart is in a suspended state under the action of magnetic force, without mechanical bearings, resulting in no friction, low heat generation, low loss, and high durability. Currently, the third-generation VADs utilizing maglev technology, including HeartWare and HeartMate3 from abroad, have achieved good results. China is also catching up in the development of the third generation VAD. I believe that with more and more independently developed artificial hearts entering the approval and clinical trial stage of the China National Medical Products Administration, they will soon be able to be applied in clinical practice, which is a great breakthrough and may greatly reduce the cost required by patients, benefiting more and more patients. (News Agency) (The author of this article is Liu Feng from Anhui Chest Hospital)
Edit：Chen Jie Responsible editor：Li Ling
Source：Xinhuanet
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