Artificial Heart

What is an Artificial Heart?

An artificial heart is a mechanical device designed to replace or assist the function of a failing human heart. It maintains blood circulation and oxygenation in the body, essentially acting as a pump to propel blood through the vascular system. Unlike the natural heart, which is a muscular organ with four chambers (two atria and two ventricles) that beats rhythmically to pump oxygenated blood from the lungs to the body and deoxygenated blood back to the lungs, an artificial heart is typically made from biocompatible materials like plastics, metals, and synthetic tissues. These devices are used primarily for patients with end-stage heart failure, where the native heart can no longer sustain life. They can serve as a temporary "bridge" to a heart transplant, a permanent "destination therapy" for those ineligible for transplants, or even allow time for the natural heart to recover.Artificial hearts are distinct from related technologies such as ventricular assist devices (VADs), which support only part of the heart; heart-lung machines used during surgery; or extracorporeal membrane oxygenation (ECMO) systems for short-term heart and lung support.

The primary goal of an artificial heart is to replicate the heart's pumping action while minimizing complications like blood clotting, infection, or device failure. Modern designs aim for durability, biocompatibility (to avoid rejection by the body), and portability, allowing patients to maintain some quality of life. As of 2025, two main total artificial hearts (TAHs) are commercially available: the SynCardia TAH and the Carmat Aeson, both approved for temporary use in specific scenarios.

History of Artificial Hearts:

The development of artificial hearts spans nearly a century, driven by the need to address heart disease—the leading cause of death worldwide—and the chronic shortage of donor organs for transplants. Early concepts emerged in the 1930s and 1940s as scientists experimented with mechanical pumps to mimic cardiac function.

• Early Experiments (1930s–1950s): The first artificial heart was implanted in a dog by Soviet scientist Vladimir Demikhov in 1938. In 1949, Yale doctors William Sewell and William Glenn constructed a rudimentary pump using an Erector Set, successfully bypassing a dog's heart for over an hour. The 1950s saw significant milestones: In 1952, the Dodrill-GMR machine (developed by Forest Dewey Dodrill and General Motors) was used in human surgery at Harper University Hospital, supporting a patient's circulation for 50 minutes during mitral valve repair—the first time a mechanical device fully maintained blood flow in a human. In 1953, John Heysham Gibbon performed the first successful open-heart surgery using a heart-lung machine. Willem Johan Kolff, known for inventing the artificial kidney, implanted an artificial heart in a dog in 1957, which survived for 90 minutes.
• 1960s Advancements: Argentine surgeon Domingo Liotta pioneered multiple designs, implanting pneumatic and electric-powered hearts in dogs starting in 1958. In 1963, Liotta and E. Stanley Crawford implanted the first clinical left ventricular assist device (LVAD) in a human. The U.S. National Institutes of Health (NIH) launched the Artificial Heart Program in 1964 to develop an implantable device. In 1966, Michael DeBakey and Liotta performed the first successful paracorporeal (external) LVAD implantation for postcardiotomy shock. On April 4, 1969, Liotta and Denton Cooley at the Texas Heart Institute implanted the first total artificial heart in a human as a bridge to transplant; the patient survived 64 hours total but died post-transplant due to infection.
• 1970s–1980s: Jarvik Era and First Permanent Implants: Kolff moved to the University of Utah in 1967, where he collaborated with Robert Jarvik. They developed the Jarvik-5 and Jarvik-7, tested extensively in animals (e.g., a calf survived 268 days in 1981). The Jarvik-7 became iconic: On December 2, 1982, William DeVries implanted it in Barney Clark, a retired dentist, at the University of Utah. Clark lived 112 days tethered to a large pneumatic console but suffered complications like seizures and bleeding. Subsequent implants included Bill Schroeder (620 days, 1984–1986) and others, highlighting issues like infection and stroke. By the mid-1980s, the NIH funded competitions for electric hearts to replace bulky pneumatic systems.
• 1990s–2000s: Refinements and Approvals: The 1990s saw FDA approvals for VADs (first in 1994). The AbioCor, a fully implantable electric TAH by Abiomed, was first used in 2001 and received humanitarian FDA approval in 2006 for non-transplant candidates. SynCardia evolved from the Jarvik-7 and gained FDA approval in 2004 as a bridge to transplant. In 2011, the Frazier-Cohn device (two modified HeartMate II pumps) was implanted experimentally.
• 2010s–Present: The Carmat Aeson, a bioprosthetic heart using bovine tissue for better biocompatibility, was first implanted in 2013. It received CE marking in Europe in 2020 for bridge use. SynCardia introduced portable drivers in 2014. Recent innovations include the BiVACOR, a rotary pump with a single moving part, first implanted in humans in July 2024, with successful bridges to transplant reported by 2025.

Types of Artificial Hearts:

Artificial hearts are categorized based on their function, design, and implantation:

1. Total Artificial Hearts (TAHs): These fully replace the native heart, removing the ventricles and valves. Examples:

• SynCardia TAH:  Pulsatile, pneumatic-powered, available in 50cc (for children/small adults) and 70cc sizes. Over 2,000 implants worldwide by 2025; longest survival exceeds 7 years. Powered by external drivers (e.g., Freedom portable system).
• Carmat Aeson: Bioprosthetic with bovine pericardium membranes and valves; hydraulic fluid driven by motors; sensors auto-adjust flow. Weighs 900g, designed for 5-year durability; approved in Europe as bridge, U.S. trials ongoing. Company faced insolvency in 2025.
• BiVACOR:  Continuous-flow rotary pump with magnetically levitated impeller; no valves, reduces clotting; first human implants in 2024–2025, with patients discharged home.
• AbioCor (Discontinued): Fully implantable, electric, with transcutaneous energy transfer; lasted 1–2 years.

2. Ventricular Assist Devices (VADs):** Assist rather than replace the heart. Types include LVADs (left ventricle), RVADs (right), or BiVADs (both). Continuous-flow models like HeartMate II/III (axial or centrifugal pumps) are smaller and more durable than pulsatile ones. Used as bridges, destination therapy, or for recovery (e.g., Berlin Heart for pediatrics, FDA-approved 2011).

3. Other Prototypes: Soft TAH (silicone 3D-printed, 2017); POLVAD (Polish pneumatic system); Phoenix-7 (1996 Taiwanese implant).

How Artificial Hearts Work:

Artificial hearts mimic the heart's dual circulation: pulmonary (to lungs) and systemic (to body). Key mechanisms:

• Pulsatile Designs (e.g., SynCardia, Jarvik-7): Use pneumatic or hydraulic pumps to create a heartbeat-like pulse. Compressed air or fluid pushes flexible diaphragms (often polyurethane or bovine tissue) to eject blood from artificial ventricles through one-way valves (e.g., mechanical or tissue). Sensors monitor pressure and adjust rate (60–120 beats/min). Power comes from external consoles via drivelines piercing the skin.
• Continuous-Flow Designs (e.g., BiVACOR, HeartMate): Use rotary impellers (axial or centrifugal) spun by magnets or motors for steady blood flow without pulses. This reduces size and mechanical wear but can affect organ function long-term due to lack of pulsatility. Speed varies (2,000–10,000 RPM) to match demand; some add pulsatility via speed modulation.
• Power and Control: Early models used large consoles (e.g., 400-pound Utahdrive). Modern ones have portable batteries (4–8 hours) recharged externally or transcutaneously to avoid infection. Internal controllers use algorithms to respond to activity levels.

Surgical implantation involves sternotomy, removing native ventricles, attaching the device to atria and great vessels, and connecting power lines. Recovery includes anticoagulation therapy and monitoring.

Challenges and Risks:

Despite progress, artificial hearts face hurdles:

• Complications: Blood clots (thrombosis), bleeding (from anticoagulants), infections (via drivelines), strokes, device malfunction, and hemolysis (red blood cell damage).
• Durability and Size: Devices must last years without failure; many are bulky, limiting use in smaller patients.
• Power Supply: External batteries restrict mobility; wireless energy transfer is emerging but not perfected.
• Cost and Access: Implants cost $100,000–$200,000; limited to specialized centers.
• Ethical Issues: Early patients like Clark endured suffering; quality-of-life debates persist.

Survival rates: For SynCardia, 1-year post-transplant survival is ~80%; without, risks rise.

Current Developments and Future Prospects:

As of November 2025, focus is on permanent TAHs and VADs. BiVACOR's 2024–2025 trials show promise for long-term use, with patients living at home. Research explores 3D-printed bioengineered hearts, stem cell integration, and xenotransplantation (e.g., pig hearts) as alternatives. The Carmat faces financial challenges but advances biocompatibility. NIH and companies like Abiomed (now part of Johnson & Johnson) invest in smaller, pulseless designs. Future goals: Fully implantable, wireless devices lasting 10+ years, reducing transplants' need. Clinical trials emphasize pediatric and destination therapy applications.