Child-Heart Disease-Virtual Heart Precision-Guides
Defibrillator Placement
'Virtual Heart' Precision-Guides
Defibrillator Placement in Children With Heart Disease
Aug. 21, 2013 — 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 Johns Hopkins researchers says it may be possible to take
the guesswork out of the process by using a virtual 3-D heart model that
analyzes a child's unique anatomy and pinpoints the best location for the
device before it is implanted.
A description of the team's work is published ahead of print
in The Journal of Physiology.
"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.,
the Murray B. Sachs Professor of Biomedical Engineering at Johns Hopkins.
"It is a critical first step toward bringing computational analysis to the
pediatric cardiology clinic."
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 Jane Crosson, M.D., a
pediatric cardiologist and arrhythmia specialist at the Johns Hopkins
Children's Center.
"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.With
the Johns Hopkins heart model, scientists say they can find exactly where in
relation to a patient's heart the device would be best able to reset the heart
by using the
least amount of energy and gentlest shock. This translates
into longer battery life for the device as well, Trayanova says.To build the
model, the Johns Hopkins team started out with simple, low-resolution MRI heart
scans of a child born without a tricuspid valve and right ventricle. Based on these
images, the researchers developed a 3-D computer model that allowed them to simulate
a dangerous rhythm disturbance during which the heart's strong, regular beats
degenerate into weak quivers that, if uninterrupted, could kill in minutes. The
model predicted how effectively the defibrillator would terminate this
dangerous rhythm when located in each one of 11 positions around the heart.
Based on the model, the scientists determined that two particular positions
rendered therapy optimal.
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 Lukas Ratner,
Fijoy Vadakkumpadan and Philip Spevak, all of Johns Hopkins.The research was
funded by the National Institutes of Health under grant number R01HL103428.
Share this story on Facebook
No comments:
Post a Comment