Coronary stents made from a novel PtCr alloy are more flexible and conformable than traditional stents. The PtCr alloy was developed by a research team that included metallurgists from NETL. The improved stents are manufactured by Boston Scientific Corporation. Photo courtesy of Boston Scientific Corporation |
A
new alloy developed by a team of researchers, including metallurgists
at the U.S. Department of Energy’s National Energy Technology Laboratory
(NETL), is helping cardiologists and their patients at home and abroad.
The novel platinum-chromium (PtCr) alloy is being used by Boston
Scientific Corporation (Natick, Mass.) to manufacture coronary stents
that are more flexible and conformable than existing stents, and more
visible on x?ray. The result: easier placement by the doctor and more
safety for the patient.
A
coronary stent is a small, expandable mesh tube that is placed in a
narrowed or weakened coronary artery, allowing the passageway to stay
open. Every year coronary stents save thousands of lives by expanding
diseased arteries and allowing blood to flow freely.
A
stent is typically inserted into an opening in the artery near the
patient’s groin, and gently maneuvered through the artery until it
reaches the site where blood flow is restricted. Once in place, a
balloon inside the tubular metal cage is inflated to expand the diameter
of the stent, opening the restricted artery and providing mechanical
support to damaged arterial walls.
For
decades, 316L stainless steel has been used successfully in a variety
of commercially available and medically approved coronary stents. The
trend in new stent designs has been to reduce stent thickness, so that
the stent delivery catheter, with the stent on it, is more flexible.
This allows the stent to be passed through more tortuous arterial paths,
thereby facilitating treatment to obstructions that were previously
untreatable by minimally invasive procedures.
But
there was a catch. As the thickness of stent walls decreased,
traditional 316L stainless steel became more difficult to see on x-ray.
This made it difficult for the doctor, who must place the stent in
precisely the right location in the artery, to see what he or she was
doing—especially when the doctor needed to insert multiple stents next
to each other in a single, extended location, or go back to further
expand or adjust the position of a stent after implantation.
Enter
NETL. More than 10 years ago, scientists at Boston Scientific called
their colleagues at NETL wanting to know if the laboratory could help
with research to improve coronary stents. Boston Scientific recognized
NETL’s metallurgy capabilities and offered to fund the entire research
project. Over the next decade, NETL and Boston Scientific worked
together to design the PtCr alloy and develop the process methodology to
produce the alloy for use as stent material.
The
PtCr alloy solves many of the past problems surrounding traditional
stents. The addition of platinum gives a stent physical properties that
allow it to be both thin and visible on x-ray. Its flexibility allows
easier movement through arterial bends without causing damage. The
addition of high-melting platinum also gives the stent a higher
corrosion resistance, which optimizes the stent’s long term stability
within the body. The alloy’s increased strength also decreases recoil,
which reduces the likelihood of constriction after deployment.
Following
a series of trials—melting, casting, fabricating, and characterizing
the properties of different alloys—and after many clinical trials,
Boston Scientific’s PROMUS ELEMENT and ION stents, made from the
novel PtCr alloy, were ready to market. Since introduction of the
improved coronary stents in January 2010, sales have exceeded $1
billion. The breakthrough was recognized by R&D Magazine, which named the PtCr alloy one of the 100 most technologically significant products to enter the marketplace in the past year.
NETL’s
materials sciences research team has done a wide variety of work in
high-temperature alloy development and processing. NETL’s materials
research includes making more effective armor for the Army, new turbine
alloys to help the Nation’s power systems operate more efficiently, and
now a medical alloy that helps save lives.
