Temporary Heart Pump Assist

This photo shows a new type of heart pump inserted with a catheter to improve the survival rate for infants undergoing a series of surgeries to correct a deadly birth defect. (Rose-Hulman Institute of Technology)Researchers have created a new type of heart pump, which is inserted with a catheter to improve the survival rate for infants undergoing a series of surgeries to correct a deadly birth defect.

The design is a viscous impeller pump for children born with univentricular circulation, a congenital heart disease that is the leading cause of death from birth defects in the first year of a child’s life. The innovation also might be used for temporarily treating adults with the disease.

The human heart normally contains two pumps, or ventricles: one circulates oxygenated blood throughout the body, and the other, less powerful, ventricle circulates de-oxygenated blood to the lungs.

Babies born with the defect have only one functioning ventricle, but French surgeon Francois Fontan discovered more than three decades ago that the infants could survive on a single ventricle by restructuring the configuration of blood vessels called the inferior vena cava and superior vena cava. The infants must have a series of three open heart surgeries performed over a period of months or years because they may not be able to survive the shock of all three surgeries at once. At least 30% of the babies do not survive the surgeries, called the Fontan procedures.

To improve the survival rate, Mark Rodefeld, a medical doctor and associate professor of surgery at the Indiana University School of Medicine, proposed in 2003 to provide a mechanical pump to assist the heart during surgery.

Such an innovation would make it possible to perform all three surgeries at the same time, while also providing a temporary heart-assist technology for adults who have had the surgeries, says Steven Frankel, a Purdue University professor of mechanical engineering. Frankel is working with Rodefeld and other researchers at the IU School of Medicine, the University of Louisville, and the Rose-Hulman Institute of Technology’s Rose-Hulman Ventures, which is developing a prototype of the pump.

The researchers have received a $2.1 million, four-year grant from the National Institutes of Health’s National Heart, Lung, and Blood Institute to continue developing the heart pump. The research also involves graduate student Jeffrey R. Kennington and Jun Chen, a Purdue assistant professor of mechanical engineering.

Researchers plan to implant the new pump into a four-way intersection where the inferior and superior vena cavae meet the right and left pulmonary arteries. Once inserted with a catheter, the pump can be dramatically expanded, forming a shape that resembles two cones joined at the base. The device spins at about 10,000rpm, connected via a slender cable to a small motor outside of the body.

Frankel and graduate student Travis Fisher originated the design, applying concepts from textbook fluid dynamics developed a century ago by Hungarian engineer Theodore von Kármán, founder of modern aerodynamics.

The researchers also found design inspiration from an unlikely source: cocktail umbrellas.

“A major challenge was, how do we get this into the body, and we thought of the cocktail umbrella,” Frankel states. “It starts out flat and compact and then opens out with a similar shape, with upper and lower segments.”

A pump is needed because relying on one ventricle reduces the heart’s circulatory force.

“A patient right now who’s walking around in their 20s, who had the surgery 20 years ago, may start having heart problems and need some support, either as a bridge to transplant or as a temporary means of support. This pump represents a way to do that in an outpatient setting. It is designed to be in the body for two weeks at most, almost like a disposable item,” Frankel explains. “The rotating device contains riblike grooves to efficiently pump blood. The design is promising because testing has shown that the rotating device causes minimal damage to red blood cells.

“Because it is larger than other experimental pumps, it does not have to spin as fast – a maximum of about 10,000rpm compared to 50,000rpm for another experimental pump – so it causes less damage to blood cells,” Frankel concludes.
 

Material was provided by Purdue University, purdue.edu.