MAGNETIC BEARINGS IN IMPLANTED PUMP MAY LET PEOPLE
WITH SERIOUS HEART DAMAGE LEAD FAIRLY NORMAL LIVES

	CHARLOTTESVILLE, Va., Feb. 17 -- A new magnetic-suspension
pump to help damaged hearts circulate blood normally is being
developed by University of Virginia engineers and the University of
Utah laboratory that treated artificial heart patient Barney Clark.
	Researchers at U.Va.'s School of Engineering and Applied
Science have made a prototype that will be further developed by the
two research teams and tested at Utah's Artificial Heart Laboratory.
Their timetable depends on a pending application for federal funds.
	Unlike the device Clark used, the new battery-powered,
surgically implanted pump would allow its user to move about freely,
said Paul Allaire, an engineering professor who leads the U.Va.
research team along with Eric Maslen, an assistant professor.
	It's the first in a new generation of continuous-flow pumps,
designed to prevent crippling or fatal side effects caused by
reliability problems in pulsing-motion pumps such as the Jarvik 7
that doctors implanted in Clark's chest in 1982, Allaire added. 
	Maslen said the U.Va.-Utah heart pump isn't the first
designed to produce a continuous flow but it is the only one in
development that is magnetically suspended, allowing it to work
without the use of bearings or lubricants, which caused harmful side
effects in previous devices.
	U.Va. researchers and the research team at Utah, headed by
Dr. Don Olsen, have filed a joint proposal for a National Institutes
of Health grant to perfect the pump and test it, first in calves.
	"Our goal is to develop a pump for long-term use, with
maximum flexibility for the patient and a minimum of side effects,"
said Allaire. "If it develops as we anticipate, it will allow
patients to live relatively normal lives for extended periods
without the need for constant supervision by medical personnel."
	Patients would wear an unobtrusive harness, resembling a
belt and suspenders, holding two batteries and a pressure regulator
outside the body. A disc-shaped pump about three inches across,
linked by wire to the power supply and regulator, would be implanted
inside the body.
	The pump's rotor, its only moving part, would be suspended
in a magnetic field. It would thus not require bearings that tend to
crush blood cells as they flow through a pump, or that may need
lubricants which can leak and contaminate the blood.
	 Two tubes within the body would connect the heart to the
pump. Blood would be pumped through one chamber of the heart at
normal pressure, circulate throughout the body and then return
through the other chamber for its next pumping cycle.
	Researchers turned to continuous-flow pumps, which use
rotary motion to propel fluids, after pulsating models such as the
Jarvik 7 were found to cause blood clots and hemorrhages. Surgeons
now use continuous-flow pumps to keep blood circulating during heart
surgery, and less often to supplement the power of failing hearts
temporarily while patients await organ transplants.
	But early generations of continuous-flow pumps had problems
with blood contamination, Allaire noted: Their bearings needed
constant lubrication, and the lubricants could leak and contaminate
the patient's blood. Saline and other solutions that usually don't
cause harmful reactions were considered, but even these can trigger
side effects unless they're sealed and kept out of the bloodstream.
	Engineering scientists then designed pumps that would use
the patient's own blood to lubricate the bearings. These also had a
dangerous failing: When blood cells were pushed through the tiny
gaps required between standard ball or roller bearings, many were
crushed and cut apart. Moreover, blood proved to be a poor lubricant
and the pumps sometimes jammed and stopped working.
	Enter magnetic bearings. These don't hold a rotor in place
within the pump by physical contact, requiring a lubricant to reduce
the friction from rubbing. They hold the rotor by suspending it
inside a magnetic field, almost as if it floats in place.
	"With magnetic bearings, blood can pass through the pump
without damage," said Allaire. "It can flow freely because the
clearance between the rotor and the wall of the pump is 30 times
wider than in a typical conventional bearing".
	There's another plus with the use of magnetic bearings, he
added. By virtually eliminating friction they reduce the energy
needed to operate a device, so the batteries used to power the heart
pump should last much longer and need fewer replacements.
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February 16, 1995