Comprehensive Introduction to the SynCardia Total Artificial Heart

The SynCardia Total Artificial Heart (TAH) represents a pinnacle of mechanical circulatory support (MCS). Unlike Left Ventricular Assist Devices (LVADs) which support a failing ventricle, the SynCardia TAH is a biventricular replacement system. It is designed to replace both the failing right and left ventricles of the human heart, effectively managing end-stage biventricular heart failure.

For patients suffering from irreversible biventricular failure—often due to complications from myocardial infarction, dilated cardiomyopathy, or congenital heart defects—the SynCardia TAH serves as a bridge to life-saving heart transplantation. By providing high-volume, pulsatile blood flow, the device maintains systemic perfusion and supports end-organ recovery while the patient awaits a donor organ.

Technical Specifications and Biomechanical Mechanisms

The SynCardia TAH is a pneumatic, pulsatile device that mimics the physiological function of the native heart. Its architecture is built upon the legacy of the Jarvik-7, refined through decades of engineering to optimize hemodynamics and durability.

Core Components

• The Pump: Two independent polyurethane ventricles (left and right) with mechanical valves.
• The Driver: An external pneumatic console (such as the Freedom® Portable Driver) that delivers compressed air to the ventricles.
• Drivelines: Percutaneous leads that connect the internal pump to the external driver, requiring meticulous exit-site care.

Hemodynamic Profile

The device operates on a fixed-rate, volume-displacement principle. Because it is a pulsatile system, it provides several advantages over continuous-flow pumps:
1. Improved Microcirculation: Pulsatility is believed to better maintain capillary perfusion.
2. Volume Capacity: It can deliver up to 9.5 liters of blood per minute, significantly higher than most LVADs.
3. Pressure Regulation: The device responds to the patient’s physiological needs by adjusting the "fill" and "eject" cycles controlled by the driver.

Clinical Indications and Surgical Applications

The SynCardia TAH is indicated for use in cardiac transplant-eligible patients with severe biventricular failure where biventricular support is required.

Surgical Procedure

The implantation is a major cardiac surgical procedure performed under cardiopulmonary bypass. The surgeon performs a median sternotomy, excises the native ventricles, and sutures the SynCardia TAH to the native atria.
* Atrial Cuffs: The device is connected to the native atria using specialized Dacron cuffs.
* Outflow Grafts: The device is connected to the aorta and the pulmonary artery via synthetic vascular grafts.
* Driveline Tunneling: The pneumatic drivelines are tunneled through the abdominal wall, creating a percutaneous exit site.

Patient Selection Criteria

Candidates must meet strict eligibility requirements:
* Irreversible biventricular failure.
* Failure of maximal medical therapy.
* Anatomic fit (the device must physically fit within the thoracic cavity).
* Psychosocial stability to manage the external driver.

Maintenance and Sterilization Protocols

Because the SynCardia TAH involves percutaneous drivelines, infection prevention is the cornerstone of long-term success.

Driveline Exit Site Care

The exit site must be monitored daily for signs of infection, such as erythema, purulent discharge, or tenderness.
* Sterile Technique: Dressing changes must be performed using sterile gloves and antimicrobial dressings (e.g., chlorhexidine-impregnated sponges).
* Stabilization: The drivelines must be secured to the patient’s body to prevent "pistoning" or movement that could introduce pathogens into the chest cavity.

Driver Maintenance

The external driver requires periodic battery charging and routine inspection of pneumatic connections. Patients are trained to respond to alarms, which indicate potential issues with air pressure, battery life, or driveline integrity.

Risks, Side Effects, and Contraindications

While the SynCardia TAH is life-saving, it carries significant clinical risks that require intensive care management.

Major Risks

1. Thromboembolism: The mechanical valves and blood-contacting surfaces carry a risk of clot formation, necessitating aggressive anticoagulation therapy (usually Warfarin and Aspirin).
2. Infection: Mediastinitis or driveline infections remain the most significant long-term threats.
3. Neurological Events: Stroke or transient ischemic attacks (TIAs) can occur due to embolic events.
4. Device Malfunction: Mechanical failure of the driver or air leaks in the pneumatic system.

Contraindications

• Irreversible multi-organ failure (renal or hepatic).
• Active, uncontrolled systemic infection.
• Contraindication to anticoagulation therapy.
• Anatomic constraints (e.g., small chest cavity preventing the pump from resting correctly).

Patient Outcomes and Quality of Life Improvements

The SynCardia TAH has revolutionized the "Bridge to Transplant" (BTT) pathway. By restoring systemic perfusion, the device often leads to:
* End-Organ Recovery: Improvement in renal and hepatic function secondary to corrected cardiac output.
* Nutritional Gains: Reduction in cardiac cachexia.
* Mobility: Once stabilized, patients can often participate in physical therapy, significantly improving their functional status prior to the rigors of a heart transplant surgery.

Data consistently shows that patients who receive the SynCardia TAH have a high probability of reaching cardiac transplantation, with survival rates comparable to those who receive a transplant without prior MCS.

Frequently Asked Questions (FAQ)

1. How long can a patient live with the SynCardia TAH?

The device is intended as a "bridge to transplant," not a permanent destination therapy. While some patients have lived for several years with the device, the goal is always to achieve a donor heart transplant as soon as possible.

2. Can a patient move around with the SynCardia TAH?

Yes. The Freedom® Portable Driver allows patients to carry the device in a backpack or shoulder bag, facilitating mobility and allowing some patients to leave the hospital while waiting for a heart.

3. What happens if the power goes out?

The driver has internal batteries and can be plugged into wall outlets or car chargers. In the event of a total system failure, the patient is trained to use an emergency manual hand-pump to drive the heart.

4. Is the SynCardia TAH noisy?

Because it is a pneumatic device, there is an audible "click" or "thump" with every heartbeat. Most patients and their families become accustomed to this sound quickly.

5. What type of medication is required?

Patients must remain on lifelong anticoagulation (blood thinners) to prevent clots from forming on the mechanical valves and interior surfaces of the pump.

6. Can a patient take a shower?

Showering is restricted due to the driveline exit sites and the sensitivity of the pneumatic equipment. Patients typically use sponge baths until the exit sites are fully healed and the clinical team approves specific showering protocols with waterproof covers.

7. How is the size of the device determined?

Surgeons use preoperative CT scans or MRIs to measure the thoracic cavity. The 70cc device is standard for most adults, while the 50cc device is used for smaller patients, including women and some adolescents.

8. What is the biggest risk with this device?

The primary risks are infection at the driveline site and thromboembolic events (strokes). These are managed through strict sterile protocols and consistent anticoagulation monitoring.

9. Does the heart have a pulse?

Yes. Unlike continuous-flow LVADs, the SynCardia TAH provides a pulsatile flow, meaning the patient will have a palpable pulse.

10. Can I exercise with the SynCardia TAH?

Physical rehabilitation is encouraged. Patients work with physical therapists to perform low-impact exercises to maintain muscle mass and cardiovascular health while awaiting a transplant.

Conclusion

The SynCardia Total Artificial Heart remains a gold-standard solution for patients with end-stage biventricular failure. Through its robust design, pulsatile hemodynamic support, and proven track record in bridging patients to transplant, it provides a critical lifeline for those who have exhausted all other medical options. Success with this device relies on a multidisciplinary approach involving cardiologists, cardiothoracic surgeons, and dedicated nursing staff, all working to ensure the patient remains stable, infection-free, and prepared for their eventual heart transplant.