A Better Way to Perform Cardiac Surgery on Children

A researcher at the University of California (UC), San Diego, has developed a new set of tools that may enhance the ability of pediatric heart surgeons to perform cardiac surgery on young patients.

Alison Marsden, a professor of mechanical and aerospace engineering at UC San Diego, developed a Y-graft for use in the Fontan procedure that will help the surgeons determine if a patient will benefit from the surgery, as well as examine how the heart will perform during moderate exercise.

This new design proposal replaced current tube grafts, which connect the inferior vena cava to the pulmonary arteries, with a Y-shaped graft. Two models of the Y-graft were examined: an “off-the-shelf” graft with 9-mm branches and an “area-preserving” graft with 12-mm branches.

The new technique was compared with two other designs currently in use: a t-junction connection of the vena cava and an offset between the inferior and superior venae cavae.

Evaluation of Y-graft hemodynamics were made at rest and during exercise with a patient-specific model, obtained from MRI and computational fluid dynamics. Four measures were observed, all of which related to the clinical setting: Fontan pressures, energy efficiency, inferior vena cava flow distribution, and wall shear stress.

The 12-mm Y-graft was more energy efficient than all of the other models at rest and during exercise. Reduction in efficiency from rest to exercise was improved by 38 percent. When compared with the other models, the 12-mm resulted in slightly larger regions of low walls shear stress, though minimum shear stress values were similar.

“Our goal is to provide a set of personalized tools that can be used in collaboration with surgeons to identify the best procedures for patients,” Marsden said.

Children who undergo the Fontan procedure typically have severe forms of heart defects that leave them with only one functional chamber, which are fatal if left untreated. Pediatric surgeons at Stanford are hoping to use the Y-graft models in a Fontan procedure for the first time later this year.

For an abstract of the journal article on the Y-graft, click here.