Jonah Patel
The total artificial heart (TAH) is a mechanical device that replaces the ventricles in the heart, taking over their function of pumping blood. TAHs are used as a bridge to transplantation for patients with biventricular failure. The invasiveness of the procedure makes it reserved for very sick patients. TAHs have been used successfully in over 1,700 patients awaiting heart transplants. However, they are not without their drawbacks, including high complication rates, poor durability, and low patient quality of life. As such, ongoing research and development are needed to improve the technology and make TAHs a viable destination therapy.
| Characteristics | Values |
|---|---|
| Definition | A total artificial heart (TAH) is a medical device used as a bridge-to-transplantation strategy for patients with biventricular failure. |
| Mechanism | A TAH replaces the ventricles, the heart's lower chambers, and takes over their job of pumping blood. |
| Use Cases | TAHs are used when the heart is unable to pump blood efficiently, which can lead to a variety of symptoms and conditions. |
| Advantages | TAHs offer greater support than other devices and remove risks associated with dysfunctional native myocardium and valves. |
| Disadvantages | Current TAH devices have high complication rates, are bulky, have poor durability and biocompatibility, and can result in low patient quality of life. |
| Availability | TAHs have been successfully used in over 1,700 patients as a temporary solution while waiting for a heart transplant. |
| Ongoing Research | Innovations in battery technology, wireless energy transmission, biocompatible materials, and soft robotics may help address the drawbacks of current TAHs. |
| Regulatory Status | The SynCardia TAH is FDA-approved for bridge to transplant, and more than 1,200 implants have occurred worldwide. |
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What You'll Learn
Total artificial hearts as a bridge to heart transplantation
Total artificial hearts (TAH) are a form of mechanical circulatory support, replacing a patient's native ventricles and valves with a pneumatically-powered artificial heart. TAHs are currently approved for use in end-stage biventricular heart failure as a bridge to heart transplantation.
TAHs offer complete mechanical circulatory support for patients with biventricular heart failure, and are primarily used on an inpatient basis at cardiac transplantation centres. They are reserved for very sick patients, for whom other treatments are not suitable. TAHs can prevent death in critically ill patients with irreversible biventricular failure who are candidates for transplantation.
TAHs have been shown to improve the rate of survival to transplantation, with a rate of 79% compared to 46% in patients with the same entry criteria who did not receive a TAH. The one-year survival rate for patients with a TAH was 70%, compared to 31% in the control group. The one- and five-year survival rates after transplantation for patients with a TAH were 86% and 64% respectively.
TAHs also eliminate problems commonly seen with ventricular assist devices, such as right heart failure, valvular regurgitation, cardiac arrhythmias, ventricular clots, intraventricular communications, and low blood flow. TAHs have been used as a bridge to transplantation in nearly 200 patients as the Jarvik-7/Symbion TAH, and since 1993, in over 225 patients as CardioWest.
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Drawbacks of current total artificial heart devices
Drawbacks of current total artificial heart (TAH) devices:
TAH devices are used as a bridge to transplantation for patients with biventricular failure. However, the current TAH devices have certain limitations that restrict their wider usage. One of the major drawbacks is the complex cardiac surgery implant procedure, which requires special training for nurses in its management and care. The invasiveness of the procedure, which involves replacing both native ventricles and valves, makes it suitable only for very sick patients.
Another issue is the high cost associated with TAH devices and their limited availability. The number of heart transplants performed worldwide has remained relatively constant, while the demand for donor hearts continues to exceed the supply due to the increasing global burden of cardiovascular disease. This has led to long wait times for patients requiring heart transplantation.
In addition, the current TAH devices have technical limitations. For instance, they require external power sources, such as batteries, which restrict the patient's mobility as they are permanently tethered to the driveline. The movement of these lines through the patient's skin can also be a source of infection. Furthermore, some healthcare providers have complained about the noise generated by the current TAH models.
While TAH devices have shown promising results in providing hemodynamic support, there have been cases of post-operative complications, such as renal failure and infections. The technical improvements required to enhance the reliability and longevity of TAH devices are still unclear, and the costs associated with these improvements remain uncertain.
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Advancements in total artificial heart technology
The total artificial heart (TAH) is a form of mechanical circulatory support that replaces a patient's native ventricles and valves with a pneumatically-powered artificial heart. Since the 1980s, TAHs have been used as a temporary solution while the patient awaits a donor heart or their heart muscle recovers function.
TAHs have been met with enthusiasm due to their potential to address the increasing global burden of cardiovascular disease and the limited number of available donor hearts. However, the adoption of TAHs has been hindered by challenges such as high costs and the complexity of the implantation procedure.
Recent advancements in TAH technology aim to address these limitations and expand the applicability of this treatment option. Here are some key advancements in TAH technology:
- Improved Patient Outcomes: TAH technology has advanced to the point where it can provide complete mechanical circulatory support for patients with biventricular heart failure. The SynCardia TAH, for example, can provide up to 9.5 L/minute of pulsatile flow, offering greater support than other ventricular assist devices (VADs). This has resulted in improved patient outcomes, with a 79% survival rate among patients bridged to transplantation using the CardioWest TAH.
- Smaller and More Efficient Devices: TAH technology is evolving to become smaller and more efficient. For instance, the SynCardia TAH is now available in a 50 cm3 variant, in addition to the original 70 cm3 version. The smaller size expands the applicability of TAHs to a wider range of patients, including those with a smaller body surface area.
- Longer Device Lifespan: Newer TAHs are being designed with longer operational lifespans in mind. The SynCardia TAH, for example, has undergone improvements to extend its lifespan, and newer TAHs in development are expected to have a lifespan of 10 to 20 years. This matches the expected lifespan of a transplanted heart and could make TAHs a more viable long-term solution.
- Reduced Power Consumption: Current TAHs and LVADs rely on external drivelines to power the device, requiring patients to carry batteries and remaining tethered to the power source. Future TAH devices are envisioned to have reduced power consumption, eliminating the need for external drivelines. Instead, transcutaneous power transmission devices, such as wearable battery belts, could be used to power the TAHs, providing patients with greater mobility and freedom.
- Total Implantability: The AbioCor implantable replacement heart represents a significant advance in TAH technology. It is a truly implantable device with no percutaneous cables, conduits, or wires. The device is motor-driven, and its orthotopic implantation allows patients complete mobility without the need for a portable controller.
- Simplified Design: Traditional TAHs and LVADs use multiple valves, which can increase the risk of infection and thrombosis. Newer TAH designs, such as the one described by Francisco Arabia, feature a simplified design with no valves and a single impeller that moves in response to oscillating electromagnetic impulses, generating a pulse similar to a natural heart.
- Expanded Applicability: TAHs are being explored as a treatment option beyond end-stage heart failure. In December 2022, a TAH implant was performed on one of the youngest pediatric patients, marking a significant milestone in the expansion of TAH applicability. TAHs are also being considered for patients who have suffered chronic rejection episodes following a previous heart transplant, offering a new chance at recovery.
These advancements in TAH technology demonstrate the ongoing innovation and progress in the field of artificial heart development. As research and development continue, TAHs may become an even more viable and accessible treatment option for patients with heart failure, offering a promising alternative to heart transplantation.
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Total artificial hearts as destination therapy
Total artificial hearts (TAHs) are implantable machines that replace the heart. They are used as a bridge to heart transplantation for patients with end-stage biventricular heart failure. TAHs offer complete mechanical circulatory support, replacing both native ventricles and valves. This invasiveness makes them reserved for very sick patients.
TAHs have been successfully used in over 1,700 patients as a temporary life-saving measure. However, despite six decades of research, a TAH suitable for destination therapy is not yet available. Major drawbacks of current TAH devices include high complication rates, bulkiness, poor durability, poor biocompatibility, and low patient quality of life. These issues have resulted in poor outcomes for TAH implants, including one patient who died 32 hours after the implant from pseudomonal sepsis.
The development of TAHs as destination therapy is an ongoing area of research. Innovations in battery technology, wireless energy transmission, biocompatible materials, and soft robotics may help overcome the drawbacks of current TAHs. For example, more powerful and compact batteries and transcutaneous energy transfer systems will improve patient quality of life by removing the need for percutaneous cables.
Two TAH devices, the CardioWest and the AbioCor, are currently undergoing clinical trials. The CardioWest is designed as a temporary device and has been successful in improving survival rates for patients awaiting transplantation. The AbioCor is a truly implantable device with no percutaneous cables, conduits, or wires, allowing patients complete mobility. It is indicated for patients not eligible for transplant who are under 75 years old and have end-stage biventricular failure.
While TAHs as destination therapy are not yet a reality, mechanical circulatory support systems, including TAHs and ventricular assist devices (VADs), play an increasingly vital role in the care of patients with end-stage heart failure. With the increasing global burden of cardiovascular disease and congestive heart failure, the demand for heart transplants far outstrips the supply of donor hearts. As such, TAHs and other mechanical circulatory support systems are crucial in managing this clinical need.
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Total artificial hearts and ventricular assist devices
Total artificial hearts (TAHs) and ventricular assist devices (VADs) are mechanical circulatory support systems (MCSSs) that have been used since the early 1980s. They serve as temporary support for patients awaiting heart transplantation or recovering heart muscle function. TAHs replace the native ventricles and valves with a mechanical pump, taking over the function of pumping blood. While TAHs have been successful in over 1,700 patients as a bridge to transplantation, they are yet to become a standard destination therapy due to various challenges.
Total Artificial Hearts (TAHs)
TAHs are implantable machines that replace the heart's ventricles, taking over the function of pumping blood when the native ventricles are not functioning properly. The TAH offers complete mechanical circulatory support, making it a viable option for patients with biventricular heart failure. It replaces both native ventricles and valves, making it a more invasive procedure reserved for very sick patients. TAHs can provide up to 9.5 litres per minute of pulsatile flow, and their large valves and short blood path reduce the risk of stasis and thrombosis.
The SynCardia TAH, for example, has undergone FDA-approved bridge-to-transplant implants in over 1,200 patients worldwide. The CardioWest TAH has also been used successfully as a bridge to transplantation, with a 79% survival rate compared to a historical control rate of 46% for patients with the same entry criteria.
Ventricular Assist Devices (VADs)
VADs are a less invasive alternative to TAHs and are more widely used. The left ventricular assist device (LVAD) is the most common type of VAD, and it assists the heart in pumping blood when it is unable to do so effectively. VADs cannot address issues with heart valves, but they are still a valuable option for patients who are not good candidates for an LVAD or are awaiting heart valve surgery.
Challenges and Future Perspectives
Despite their life-saving potential, TAHs and VADs face several challenges. High complication rates, bulky devices, poor durability, poor biocompatibility, and low patient quality of life are some of the drawbacks that limit the widespread adoption of TAHs as destination therapy. Additionally, the costs of research and development (R&D) for TAHs and VADs are substantial, and determining future R&D costs is challenging.
However, ongoing innovations in battery technology, wireless energy transmission, biocompatible materials, and soft robotics offer promising opportunities to address the current limitations of TAHs. While five-year models appear possible in the near term, achieving highly reliable 5- to 10-year devices will require advancements in engineering and materials science.
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Frequently asked questions
A total artificial heart (TAH) is a mechanical device that replaces the ventricles, or lower chambers, of the heart. It takes over the job of pumping blood when the heart is no longer able to do so efficiently.
A total artificial heart is powered by a portable air compressor (driver) that is placed outside the body. The driver pushes air through tubes, known as drivelines, which connect the artificial heart to the driver and keep the blood pumping at a steady rhythm.
A total artificial heart is typically considered for patients with end-stage heart disease or biventricular failure. It is used as a bridge to transplantation, helping patients stay alive and healthy enough for a heart transplant when a donor heart becomes available.
A total artificial heart offers complete mechanical circulatory support, removing the risks associated with a dysfunctional native heart. It can also provide greater support and improve quality of life compared to other devices such as ventricular assist devices (VADs).
Current TAH devices have limitations such as high complication rates, bulkiness, poor durability, poor biocompatibility, and a negative impact on patient quality of life. These factors need to be addressed before TAHs can be widely adopted as a long-term solution or destination therapy.
