The small size and abnormal anatomy of children born with heart defects often force doctors to place lifesaving defibrillators entirely outside the heart, rather than partly inside -- a less-than-ideal solution to dangerous heart rhythms that involves a degree of guesstimating and can compromise therapy.
Now, by marrying simple MRI images with sophisticated computer analysis, a team of
A description of the team's work is published ahead of print in
"Pediatric cardiologists have long sought a way to optimize device placement in this group of cardiac patients, and we believe our model does just that," says lead investigator Natalia Trayanova, Ph.D. (http://www.hopkinsmedicine.org/heart_vascular_institute/research/research_retreat/speakers/trayanova.html), the Murray B. Sachs Professor of Biomedical Engineering at
If further studies show the model has value in patients, it could spare many children with heart disease from repeat procedures that are sometimes needed to re-position the device, says co-investigator
"It's like having a virtual electrophysiology lab where we can predict best outcomes before we even touch the patient," Crosson says.
In adults and in children with normal size and heart anatomy, one part of the device lies under the collar bone, while the other end is inserted into one of the heart's chambers, a standard and well-tested configuration. But in children with tiny or malformed hearts, the entire device has to be positioned externally, an often imperfect setup. Such less-than-precisely positioned defibrillators can fire unnecessarily or, worse, fail to fire when needed to shock a child's heart back into normal rhythm, experts say. In addition, devices that are not positioned well can pack a punch, delivering ultra-strong, painful jolts that frighten children and could even damage heart cells.
"These are lifesaving devices but they can feel like a horse kick to the chest and really traumatize children," Crosson says.
To build the model, the
A particular advantage of the model is its true-to-life complexity. The model was built using digital representations of the heart's subcellular, cellular, muscular and connective structures -- from ions and cardiac proteins to muscle fiber and tissue. The computer model also included the bones, fat and lungs that surround the heart.
"Heart function is astounding in its complexity and person-to-person variability, and subtle shifts in how one protein interacts with another may have profound consequences on its pumping and electric function," Trayanova says. "We wanted to capture that level of specificity to ensure predictive accuracy."
Trayanova and her team also have designed image-based models that pinpoint arrhythmia-triggering hot spots in the adult heart muscle and can help guide therapeutic ablation of such areas. The new pediatric virtual heart, however, is the team's first foray into pediatric cardiology.
Co-investigators on the research included
The research was funded by the
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