Magnetocardiography accurately diagnosed long QT syndrome (LQTS) in fetuses, according to a study published online Nov. 12 in Circulation.

Researchers led by principal investigator Ronald T. Wakai, PhD, of the University of Wisconsin School of Medicine and Public Health in Madison, obtained the records of 30 high-risk fetuses sent for fetal magnetocardiography (fMCG) at the University of Wisconsin-Madison and at two locations in Japan between 1996 and 2012. They compared prenatal heart rate and reactivity, cardiac time intervals, characteristics of T waves and Torsades de Pointes to echocardiographic findings after birth. They also genetically tested newborns for LQTS mutations.  

Using the fMCG accurately diagnosed LQTS 89 percent of the time. Genetic testing verified this finding. Four fetuses with a corrected QT segment of 620 milliseconds or more experienced Torsades de Pointes frequently, and these episodes were present 22 to 79 percent of the time. fMCG also identified Torsades de Pointes in 18 percent of fetuses with a significant LQTS family history, but negative echocardiographic findings prior to fMCG.

The testing allowed the fetuses to be treated in utero with medications to control the rhythm that enabled delivery at an optimal time and appropriate postnatal care.

Wakai and colleagues said that their findings suggest fMCG is a valuable diagnostic tool for identifying fetuses with LQTS and Torsades de Pointes.

While he said the findings are promising for clinical use of fMCG, Wakai said in a press release that an accurate and comprehensive family history is crucial for diagnosing LQTS.