Now, researchers at the University of Wisconsin-Madison are developing a new technique to diagnose and treat dangerous heart rhythms in the womb.
Long QT syndrome
, an abnormal heart rhythm present in about one in every 2,000 newborns, has been linked to stillbirths and sudden infant death syndrome. The study
is the first to document the electrophysiological characteristics of fetal long QT syndrome and to evaluate the diagnostic accuracy of a magnetocardiogram, or MCG, in a sizable population of at-risk fetuses.
With this promising new technology, physicians may be able to diagnose and possibly even treat the condition, according to research published in the American Heart Association journal Circulation.
“Until now, physicians were unable to diagnose a serious heart condition known as long QT syndrome until after birth,” said Ronald T. Wakai,
principal investigator of the study and a professor of medical physics at the University of Wisconsin School of Medicine and Public Health in Madison. “Our study shows that you can diagnose the condition in utero and identify which fetuses are most likely to have life-threatening arrhythmia. We also showed that once detected, the arrhythmia can be effectively treated in utero.”
An ultrasound cannot diagnose long QT syndrome, and EKGs aren’t effective in measuring fetal electrical activity because of the vernix, an insulating, wax-like coating that protects the skin of the fetus.
Using the MCG, the researchers diagnosed long QT in the womb with 89 percent accuracy.
The researchers evaluated 30 pregnancies from 1996 to 2012 in Wisconsin and at two locations in Japan. They chose patients based on a family history of long QT syndrome, unexplained death of a sibling in infancy or childhood, or a suspicious fetal heart rhythm. They then collected data, positioning a probe on the mother’s abdomen as early as midway through the pregnancy.
Long QT syndrome was diagnosed in 21 of the fetuses. Six of the fetuses had dangerous heart rhythms and one was delivered early after threatening rhythms were noted.
MCG also enabled definitive diagnosis of Torsades de Pointes (TdP), long QT syndrome’s signature rhythm, “despite its transient and variable nature, which prompted appropriate, effective in-utero pharmacologic therapy. Importantly, TdP was detected in 18 percent of subjects with long QT family history, but negative echocardiographic surveillance before [fetal] MCG evaluation,” the study reported.
The technology isn’t in the clinic yet, largely due to its high cost. Wakai believes, however, that a cheaper detector, known as an atomic magnetometer, can be just as effective
at producing MCG recordings. Wakai is working with UW physicist Thad Walker and QuSpin Inc., a Colorado-based company, to develop prototypes that could be ready for testing by early next year.
Co-authors are Drs. Bettina F. Cuneo; Janette F. Strasburger; Suhong Yu; Hitoshi Horigome; Takayoshi Hosono; and Akihiko Kandori.
The National Institutes of Health funded the study.
University of Wisconsin School of Medicine and Public Health