Children born with univentricular hearts typically have to undergo a multi-staged Fontan repair to fix the defect. Usually, the first stage is a creation of a bidirectional Glenn shunt, and the second stage is Fontan completion. (To learn more about the Fontan, check this Wikipedia entry.) Survival rates are still low, but researchers at Purdue University have created a tiny heart pump that should help the heart during the perioperative and postoperative period. The basic problem with Fontan physiology is a univentricular circulation that features systemic venous hypertension and pulmonary arterial hypotension. So, investigators at Purdue thought that they might improve cardiac performance and systemic and pulmonary perfusion by augmenting cavopulmonary circulation, and providing a modest increase in ventricular filling by implanting a so-called von Kármán viscous impeller pump. Such a cavopulmonary pump can raise filling pressures only 2 to 5mmHg, and that in itself can provide the necessary pressure gradient boost to restore circulation to better resemble a normal two-ventricle physiology.
If everything goes according to plan, the percutaneous catheter delivered pump may allow all stages of Fontan to be done in one go, hopefully leading to much better outcomes. It is also hoped that older people with the condition may benefit from having this device implanted for continuous use.

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 10,000 rpm, connected via a slender cable to a small motor outside of the body.
Frankel [Steven Frankel, Purdue University professor of mechanical engineering] 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 said. "It starts out flat and compact and then opens out with a similar shape, with upper and lower segments."
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’s larger than other experimental pumps, it doesn’t have to spin as fast – a maximum of about 10,000 rpm compared to 50,000 for another experimental pump – so it causes less damage to blood cells,” Frankel said. “It’s like the gentle cycle in a washing machine.”
Experiments at the University of Louisville that mimic the circulatory system show the degree of damage done to blood cells by the spinning pump is acceptable for clinical use.

Press statement from Purdue: New heart pump to provide temporary assist for infants, adults …
Article in Journal of Thoracic and Cardiovascular Surgery: Cavopulmonary assist for the univentricular Fontan circulation: von Kármán viscous impeller pump