Transcatheter heart valves use nylon, UHMWPE

Plastics are playing a critical role in new artificial heart valves that prop open diseased valves and can be inserted with a catheter that is snaked through arteries, a procedure called transapical aortic valve implantation.

The most advanced is the Sapien Heart Valve from Edwards Lifesciences Corp. (Irvine, CA), which was launched for inoperable patients in the U.S. last year.  According to a patent application, a liner and tubing in

the heart valve are made of a nylon block copolymer while a coil is produced from stainless steel. Bovine tissue is also used.

The new minimally invasive approach may replace conventional heart valve surgery in which an incision is made through the patient's sternum and the patient's heart is stopped while blood flow is rerouted through a heart-lung bypass machine.

Risks from open heart surgery include bleeding, infection, stroke, heart attack, arrhythmia, renal failure, adverse reactions to the anesthesia medications, as well as sudden death. An estimated 2-5% of patients die during surgery.

Edwards Lifesciences announced last month that new data show positive results on high-risk surgical patients with severe aortic disease who were treated with its transapical transcatheter aortic valve replacement (TAVR).

"It is encouraging that, in this much larger group of patients treated with transapical valve replacement, investigators observed a trend toward patients feeling better faster and having improved outcomes. We believe this more recent experience adds strong new support to the transapical procedure as an important option for patients who are at high-risk for surgery," said Michael A. Mussallem, Edwards' chairman and CEO.

The polyamides in the Sapien heart valve are usually based upon nylon-11 but may be based upon nylons 6 of nylon-6,6 or even a copolymer such as nylon-6/nylon-11. The polymers range in hardness as measured in durometer from Shore A 60 to Shore D72.

Fiber-based valve

Separately, DSM and University Medical Center Utrecht announced that UMC Utrecht will develop and evaluate a prototype of a non-biological supportive scaffold for the minimally invasive treatment of vascular diseases using Dyneema Purity fiber.

UMC Utrecht says it chose Dyneema Purity fibers for designing heart valve and blood vessel wound closure devices because of their strength, high flex fatigue resistance, low elongation, minimal profile and tear resistant properties.

The end goal of this collaboration is to build up know-how and assess the preclinical feasibility of a fiber-based heart valve. Once feasibility is shown, DSM and UMC Utrecht said they will jointly reach out to medical device companies to explore options for further development.

"We believe that heart valves with scaffolding made from Dyneema Purity fibers have the potential to lead to a revolutionary new solution, giving those dealing with heart disease the benefit of a less invasive transcatheter heart valve replacement. Although we are in a very early feasibility stage and prototyping only, we believe Dyneema Purity fiber is a very interesting material to use as basis for this feasibility study," said Principal Investigator Paul Gründeman of the Heart and Lungs Division at UMC Utrecht.

Dyneema is made from ultra-high-molecular-weight polyethylene (UHMWPE).