Segmented polyurethane solution — the primary material used to manufacture the SynCardia temporary Total Artificial Heart (TAH) — is strong, durable and uniquely suited for use inside the human body.
As a clinically-proven, life-saving treatment option for end-stage biventricular heart failure, patients depend on the SynCardia TAH to provide reliable, long-term support while they wait for a matching donor heart.
The secret behind the success of the SynCardia TAH is segmented polyurethane solution, also known as SPUS. Made in a laboratory at SynCardia headquarters in Tucson, Arizona, SPUS has a high degree of fatigue resistance, strength and biocompatibility, making it an ideal material for manufacturing multiple components of the TAH.
How SPUS is Made
The original formulation of SPUS was developed for use in the textile industry — in fact, you may be familiar with one if its close relatives, Spandex (also known as Lycra). Because of its excellent physical and mechanical properties and biocompatibility, researchers recognized the compound’s potential for medical applications and began testing and refining it for use in early artificial hearts.
Today, a highly-refined, proprietary formulation of SPUS is used exclusively in the SynCardia TAH — the only commercially approved total artificial heart available today. The solution is made in an 11-foot-tall reactor, which allows SynCardia to control critical factors like temperature, mixing speed and humidity according to the formula’s exact specifications.
Each Batch of SPUS Undergoes Comprehensive Testing
After the manufacturing process is complete, every batch of SPUS undergoes extensive testing and quality measures before it is approved for use in TAH manufacturing. In total, SPUS must pass 12 different tests on the physical, chemical and molecular levels to ensure that it meets required specifications.
These tests require the compound to withstand forces and pressures significantly greater than anything it will actually experience in the human body. For example, when implanted in a patient, the SPUS diaphragms in the TAH will typically experience force between 2 and 6 pounds per square inch (psi), which is the amount of pressure produced by the driver that pumps the TAH. This is well below what SPUS can withstand before damage occurs, which is typically between 500 to 750 psi of force.
Additional tests of material strength include tear, tensile and yield. In order to be approved for use in TAH manufacturing, each new batch of SPUS must be capable of withstanding:
- At least 350 pounds per inch of force before tearing (tear test)
- At least 5,000 psi of force before breaking when stretched (tensile test)
- At least 500% elongation from its original length before it breaks or fails (yield test)
For patients with end-stage biventricular heart failure in need of an immediate transplant, the SynCardia TAH can be a life-saving treatment option; however, because of the shortage of donor hearts, many of these patients will need to wait weeks, months or even years for a matching donor heart to become available.
Several patients have been supported by the SynCardia TAH for more than four years while awaiting a heart transplant. To put that in perspective, when set at a typical beat rate of 130 beats per minute, the TAH diaphragms will beat more than 273.3 million times over a four-year period.
By utilizing a material capable of withstanding pressures and environments far more extreme than those found within the human body, SynCardia is able to offer patients a total artificial heart capable of providing the support they need while they await their donor heart transplant.