University of Florida students build smaller, smarter heart pump
1 May, 2005
Gainesville, Fla. ,USA. A miniaturized heart pump designed by a team of
University of Florida engineering students could become a life-saving
alternative for patients waiting in long lines for scarce donor hearts.
The UF team is creating a device with a novel pumping technology that
makes it smaller and smarter than currently available ventricular assist
devices, which are too large to be implanted in many patients. The pump’s
small size means also it would be the first such device in the U.S. that
could be used in children.
“Current (heart pumps) are really large and complicated, so we’re aiming
to build one that’s smaller and allows more types of applications,” said
mechanical and aerospace engineering student Ella Kinberg, the project’s
Ventricular assist devices, or VADs, are connected to a patient’s
diseased heart, internally or externally, and help it to pump blood.
Although most VADs are used to sustain a patient’s life until a donor heart
becomes available, they also can help patients recover from trauma such as
open heart surgery, eliminating the need for a transplant. VADs also are
being developed to act as long-term replacement hearts, a process known as
The UF student team designed the device as part of the College of
Engineering’s yearlong Integrated Process and Product Design, or IPPD,
program, a government- and corporate-sponsored research and education
program. The team’s goal was to design a smaller, more efficient version of
an innovative prototype pump originally conceived by UF biomedical
engineering doctoral student Mattias Stenberg, who acted as a project
Stenberg designed the original device in 1999 while working with UF
mechanical and engineering professor Roger Tran-Son-Tay. Stenberg returned
to UF in 2004 to develop and test the prototype with Tran-Son-Tay and UF
College of Medicine assistant professor Charles Klodell. Both Tran-Son-Tay
and Klodell were faculty advisers on the IPPD project.
“The one thing that (this pump) has that no other pump has is continuous
inflow with pulsating outflow,” Klodell said. “It has a continuous
pre-filling chamber, something that nobody else has come up with.”
In a human heart, oxygen-rich blood enters the left atrium from the lungs
and is pumped out to the body through the left ventricle. The pump prototype
was modeled after this system, using a dual-chamber design that enables the
pump to fill throughout the pumping cycle. A push-plate valve moves fluid
into the main pumping chamber, allowing the filling to transition easily and
Standard displacement pumps fill during the diastole phase of the pumping
cycle, when the heart is relaxed, but not during the systole phase, when it
contracts. Consequently, displacement pumps need to fill the same volume,
but in half the time, Stenberg said.
With a continuous inflow, the UF pump is able to reduce the pressure on
the blood while injecting it into the pump – an important modification
because higher pumping pressure could cause damage to the red blood cells,
thereby starving the body for oxygen, he said.
The pulsating outflow allows for greater control over fluid volume
passing through the pump. The pump is sensitive to changes in inflow
pressure as well, such as during times of increased activity, so that if the
pressure increases, it starts to pump more blood – a self-regulating feature
also copied from the way a human heart behaves.
The design “offers the mechanical reliability and the pulse-style flow of
traditional displacement pumps with the potential for significant
miniaturization,” Klodell said.
The size of the pump is restricted by available space in the abdominal
cavity. Most adults can’t receive a currently available VAD, which requires
a body surface area of 1.5 square meters, Stenberg said. For pediatric use,
that size shrinks to 0.7 square meters.
Once the new pump has been thoroughly tested in the laboratory, the next
step will be to implant the pump in a pig for live, in vivo testing. The
final step in the testing, human trials, may begin within 18 to 24 months,
There is great need for smaller, more flexible and durable VADs, Stenberg
said. “Currently we do about 2,200 heart transplants per year, but we have
about 5,000 people on the donor waiting list,” he said. “If you take a look
at how many patients have end-stage heart failure, that figure goes up to
50,000 in the U.S. alone.”