In utero diagnosis of long QT syndrome by magnetocardiography

Circulation. 2013 Nov 12;128(20):2183-91. doi: 10.1161/CIRCULATIONAHA.113.004840.


Background: The electrophysiology of long QT syndrome (LQTS) in utero is virtually unstudied. Our goal here was to evaluate the efficacy of fetal magnetocardiography (fMCG) for diagnosis and prognosis of fetuses at risk of LQTS.

Methods and results: We reviewed the pre/postnatal medical records of 30 fetuses referred for fMCG because of a family history of LQTS (n=17); neonatal/childhood sudden cardiac death (n=3), or presentation of prenatal LQTS rhythms (n=12): 2° atrioventricular block, ventricular tachycardia, heart rate < 3(rd) percentile. We evaluated heart rate and reactivity, cardiac time intervals, T-wave characteristics, and initiation/termination of Torsade de Pointes, and compared these with neonatal ECG findings. After birth, subjects were tested for LQTS mutations. Based on accepted clinical criteria, 21 subjects (70%; 9 KCNQ1, 5 KCNH2, 2 SCN5A, 2 other, 3 untested) had LQTS. Using a threshold of corrected QT= 490 ms, fMCG accurately identified LQTS fetuses with 89% (24/27) sensitivity and 89% (8/9) specificity in 36 sessions. Four fetuses (2 KCNH2 and 2 SCN5A), all with corrected QT ≥ 620 ms, had frequent episodes of Torsade de Pointes, which were present 22-79% of the time. Although some episodes initiated with a long-short sequence, most initiations showed QRS aberrancy and a notable lack of pause dependency. T-wave alternans was strongly associated with severe LQTS phenotype.

Conclusions: Corrected QT prolongation (≥490 ms) assessed by fMCG accurately identified LQTS in utero; extreme corrected QT prolongation (≥620 ms) predicted Torsade de Pointes. FMCG can play a critical role in the diagnosis and management of fetuses at risk of LQTS.

Keywords: alternan; arrhythmias, cardiac; fetus; long QT syndrome; magnetocardiography; torsades de pointes.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Anti-Arrhythmia Agents / therapeutic use
  • Cohort Studies
  • Electrocardiography
  • Female
  • Fetal Diseases / diagnosis*
  • Fetal Diseases / drug therapy
  • Fetal Diseases / genetics
  • Genetic Association Studies
  • Heart Rate, Fetal
  • Humans
  • Infant, Newborn
  • Lidocaine / therapeutic use
  • Long QT Syndrome / diagnosis*
  • Long QT Syndrome / drug therapy
  • Long QT Syndrome / genetics
  • Magnetocardiography / methods*
  • Male
  • Pregnancy
  • Prenatal Diagnosis / methods*
  • Refractory Period, Electrophysiological
  • Retrospective Studies
  • Sensitivity and Specificity
  • Torsades de Pointes / diagnosis*
  • Torsades de Pointes / drug therapy
  • Torsades de Pointes / genetics


  • Anti-Arrhythmia Agents
  • Lidocaine