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Five teams working on pumps for kids' hearts
Thursday, April 29, 2004

A quarter. A dime. An AA battery.

Aside from being things you might fish out of a pants pocket, these items approximate the size and shape of an array of heart pumps now being developed to save the lives of the smallest heart patients.

  
Online Graphic:
Pediatrictic heart pump

See a graphic that shows the size of a heart pump under development.

 
 
A team from the University of Pittsburgh, Children's Hospital and Carnegie Mellon University is one of five research groups awarded five-year contracts this week by the National Heart, Lung and Blood Institute to build devices that would keep sick babies alive until their hearts can heal or they can undergo heart transplantation.

The Pittsburgh team, for instance, is receiving $4.5 million to develop a heart pump the size of a quarter, which could be implanted in children and infants as small as five pounds and operate for up to six months.

Heart pump technology for adults has developed rapidly in the last decade. The pumps, known as ventricular assist devices, not only are widely used as a "bridge to transplant," but also have been approved for use as an alternative to heart transplantation.

The pumps are too big for most pre-adolescent children, however, and the technology is not easily scaled down.

"For kids waiting for transplants ... there are very few options available," said Dr. Tracey Hoke, a pediatric cardiologist and medical officer for the heart institute's pediatric circulatory support program.

In addition to the Pittsburgh team, groups from Penn State University, the Cleveland Clinic and Jarvik Heart Inc. are also developing pediatric heart pumps for the institute. Ension Inc., a spinoff from Pitt that is located in Harmar, received a $3.7 million contract to develop an advanced version of the only existing mechanical support for small children, a technology known as extracorporeal membrane oxygenation, or ECMO.

"At the moment, if somebody starts deteriorating in front of your eyes, there's no way to keep them alive other than ECMO," said Dr. Steven Webber, medical director of heart transplantation at Children's Hospital.

Even with ECMO ---- basically, the same heart-lung machine used to sustain patients during open heart surgery ---- a child can't be kept alive for more than two weeks. ECMO can cause dangerous blood clots; thinning the blood to prevent clots can, in turn, cause bleeding episodes.

With donor hearts in short supply, the lack of long-term support technology means about a quarter of all pediatric transplant candidates die on the waiting list, Webber noted. About 250 children undergo heart or heart/lung transplants each year.

In addition to transplant candidates, heart pumps could help children with viral infections of the heart, called myocarditis. Heart pumps could help keep them alive for a few weeks ---- long enough for the infections to clear, Hoke said. Myocarditis cases peak at age 2.

Harvey Borovetz, Pitt's chairman of bioengineering, said federal funding is essential for developing pediatric heart pumps because the number of children who need them are too few to attract private investment.

Several pediatric pumps have been developed in Europe, but are not available here. Last month, surgeons at Texas Children's Hospital in Houston implanted a smaller version of an adult-size pump made by MicroMed Technology into a 6-year-old girl, who subsequently died. That pump is not suitable for the smallest patients and will require far more testing before it can be marketed, said William J. Weiss, co-director of bioengineering at Penn State's Hershey Medical Center.

Borovetz is leading the development of the heart pump at Pitt's Magowan Institute for Regenerative Medicine, heading a team that includes Carnegie Mellon bioengineer James Antaki and, among others, a Utah device manufacturer called MedQuest Products.

The device would be a centrifugal flow pump with a magnetically levitated impeller. The electrical pump would be implanted below the heart, draining blood from the heart's main pumping chamber and then pumping it into the body's main artery, the aorta.

Jarvik Inc. of New York City is working with Dr. Bartley Griffith of the University of Maryland, formerly Pitt's chief of cardiovascular surgery, on a $5 million contract to develop an implantable pump the size of an AA battery. It could treat children as young as a few years old. An even smaller version is envisioned for infants.

The Cleveland Clinic's "PediPump" would be smaller still ---- about the size of a dime ---- yet capable of sustaining children of any age, from infants on up to young adults, said Dr. Brian Duncan, a pediatric heart surgeon. That contract is for $4.2 million.

Penn State's Hershey Medical Center is receiving $5 million to develop an external heart pump. It would be a child-size version of a pneumatically driven, pulsatile pump for adults that Penn State developed in the 1970s and is now sold by Thoratec Corp., Weiss said.

The National Heart, Lung and Blood Institute's Hoke said clinical trials are not part of the five-year contracts issued this week, though the pumps could be made available within each institution on a compassionate use basis. Presumably, two or three of the devices will eventually undergo clinical testing, she added.


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First published on April 29, 2004 at 12:00 am
Post-Gazette science editor Byron Spice can be reached at bspice@post-gazette.com or 412-263-1578.