COLUMBUS, Ohio -- Researchers have found a new way to diagnose potentially
dangerous heart murmurs in children.
Cardiologists at Ohio State University and Children's Hospital of Columbus
used a computer that analyzes heart sounds to tell the difference between
those sounds caused by a heart defect and "innocent" heart murmurs
that pose no threat.
This study, which recently appeared in The American Journal of Cardiology,
was the first time researchers have used a technique called digital acoustic
cardiography (DAC) to diagnose heart murmurs in children. The research team
included Douglas A. Balster, an Ohio State medical student; David P. Chan
and Daniel P. Rowland, assistant professors of pediatrics; and Hugh D. Allen,
professor and vice chair of pediatrics.
Chan and his colleagues used DAC to analyze the heart sounds of 58 children
-- 30 with innocent murmurs, and 28 with ventricular septal defects (VSDs),
holes between the heart's two lower chambers. VSDs are the most common heart
defect found in children.
The technique was 93 percent effective in separating innocent murmurs from
those caused by VSDs.
With DAC, a computer converts the digital signal of heart sounds into a
graphical display which cardiologists can use to pick out the most intense,
high-frequency signals simply by looking for the brightest colors.
"There are very few pediatric cardiologists in remote areas, because
it's such a specialized practice," said Chan. "So the biggest
potential use of this instrument is for family doctors to record the heart
sounds of children, and send the recording to a distant cardiologist who
can then diagnose the murmur."
But Chan says DAC isn't a replacement for an in-person visit to a heart
specialist.
"I don't think the DAC instrument replaces a cardiology evaluation
in any way. It is simply a tool that allows us to be more confident in screening
children to determine if they need to be seen in person by a cardiologist,"
said Chan.
Families can avoid expensive travel and medical consultations if DAC diagnoses
their child with an innocent murmur. They can also forego more expensive
medical tests.
Right now, most children undergo an electrocardiogram (ECG) whenever a doctor
hears a murmur, but ECGs aren't very sensitive. Family doctors often order
a chest x-ray as well, but many children with heart defects have normal-looking
chest x-rays.
DAC is especially good at recording heart sounds because it uses microphones
that don't pick up extraneous sounds from the examination room. Doctors
tape the microphones to a child's chest at the same locations they normally
listen with a stethoscope, and record about 30 seconds of heart sounds.
DAC then analyzes the frequency and intensity of the sounds.
The frequency and intensity of a murmur reflect the amount of turbulence
in the blood as it flows across a hole in the heart. For instance, blood
rushing though a pin-sized hole makes a loud, high-frequency sound that
shows up as a patch of bright color on a DAC display.
In the study, DAC correctly identified every case of ventricular septal
defect, but 7 percent of the time it classified an innocent murmur as a
VSD, which Chan said is acceptable.
"We would rather say there is a problem and find out later that we
were wrong, than miss a child with a true heart disease," said Chan.
Chan says that the technique may be adopted by major medical centers over
the course of the next two years. "There's still much to learn about
what DAC is capable of and what its limitations are," said Chan.
In the next phase of the research, Chan and his colleagues will examine
children with valve defects and other heart problems.
Children with serious heart defects ultimately need open-heart surgery.
Children with small holes may never need surgery, but they do need to be
examined regularly by a cardiologist. They might also need to take antibiotics
before dental procedures to prevent infections of the heart.
"Our goal is to care for children to the best of our ability,"
said Chan. "And that means that we need to be absolutely certain that
we're not missing a single child with a heart problem that needs care."
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Contact: David P. Chan, (614) 722-2530; Chan.57@osu.edu
Written by Pam Frost, (614) 292-9475; Frost.18@osu.edu