Now, researchers at the University of Wisconsin School of Medicine and Public Health in Madison say they have been able to both diagnose and treat the condition while the baby is still in the womb.
"Until now, physicians were unable to diagnose a serious heart condition known as long QT syndrome until after birth," Ronald T. Wakai, principal investigator of the study and a professor of medical physics, said in an American Heart Association news release. "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."
The researchers say they are the first to test the diagnostic accuracy of the magnetocardiogram, also called magnetic EKG, in a sizable population of at-risk fetuses. They studied 30 pregnancies between 1996 and 2012 in Wisconsin and in Japan, choosing patients based on family history, suspicious fetal heart rhythm, or unexplained death of a sibling in young childhood.
Normally, the QT interval lasts about a third of each heartbeat cycle. When the heart rate accelerates, the QT interval shortens. When someone has an abnormally long QT interval, this can trigger the heart to beat faster to try to keep up, hence the arrhythmic beat. Basically, the heart works harder to recharge after sudden changes in heart rate, in some instances to the point of cardiac arrest and even death.
Using the magnetic EKG to assess the heart's electrical system, the researchers report in the American Heart Association journal Circulation that they diagnosed long QT in utero in 21 of the fetuses, six of whom had dangerous arrhythmias and one who was delivered early because of this. They say they were able to make these diagnoses with 89 percent accuracy.
Wakai says that while magnetic EGKs are likely to be used in the "not-too-distant future," family history will still be the most important part of diagnosis.
"There is no cure for long QT syndrome itself, but it is associated with sudden death because it makes the heart susceptible to a lethal arrhythmia known as Torsade de Pointes (TdP)," said Wakai in an e-mail. In this study, he added, the arrhythmias were treated by giving the mother antiarrhythmic drugs, which cross the placenta to treat the fetus.