Repolarization Predictors of Fetal Long QT Syndrome.

Background: Diagnosis of fetal long QT syndrome (LQTS) using fetal magnetocardiography (fMCG) is straightforward in cases of overt QTc prolongation accompanied by LQTS rhythms; however, cases of isolated QTc prolongation can be challenging.

Objective: To characterize repolarization in normal and phenotype-positive LQTS fetuses with the goal of utilizing additional parameters of repolarization to improve the accuracy of fMCG diagnosis of LQTS.

Methods: FMCG recordings were taken from 37 phenotype-positive fetuses with confirmed LQTS and 132 normal controls.

Dynamics of the use of magnetocardiography in the study of the cardiac conduction system of the chick embryo.

Introduction: Human fetal magnetocardiography (fMCG) has been done for several decades to evaluate fetal arrhythmias using a superconducting quantum interference device (SQUID) magnetometer, but there is little work in embryonic/fetal animal models. This study uses an optically-pumped magnetometer (OPM) to obtain an fMCG in the chick embryo.

Methods: White Leghorn chick embryos were examined from incubation Day #10-19.

Low-Cost Fetal Magnetocardiography: A Comparison of Superconducting Quantum Interference Device and Optically Pumped Magnetometers.

Background Fetal magnetocardiography (fMCG) is a highly effective technique for evaluation of fetuses with life-threatening arrhythmia, but its dissemination has been constrained by the high cost and complexity of Superconducting Quantum Interference Device (SQUID) instrumentation. Optically pumped magnetometers (OPMs) are a promising new technology that can replace SQUIDs for many applications. This study compares the performance of an fMCG system, utilizing OPMs operating in a person-sized magnetic shield, to that of a conventional fMCG system, utilizing SQUID magnetometers operating in a magnetically shielded room.

Fetal QT Interval Estimation Using Sequential Hypothesis Testing.

: Recent studies utilizing fetal magnetocardiography have demonstrated the efficacy of corrected QT interval (QTc) measurement for in utero diagnosis and prognosis of long QT syndrome, a leading cause of sudden death in early life. The objective of the study was to formulate and test a novel statistical estimation method to detect the end of the fetal T-wave and thereby improve the accuracy of fetal QT interval measurement. : To detect the end of the T-wave, we apply a sequential composite hypothesis test to decide when the T-wave has returned to baseline.

Fetal Atrial Flutter: Electrophysiology and Associations With Rhythms Involving an Accessory Pathway.

Background: Atrial flutter (AFl) accounts for up to one third of all fetal tachyarrhythmias and can result in premature delivery, hydrops, and fetal death in 10% of cases; however, the electrophysiology of AFl in utero is virtually unstudied.

Methods And Results: In this observational study, we reviewed 19 fetal magnetocardiography studies from 16 fetuses: 15 fetuses (21-38 weeks' gestation) referred with an echocardiographic diagnosis of AFl and 1 fetus (20 weeks' gestation) referred with a diagnosis of tachycardia that was shown by fetal magnetocardiography to have transient AFl in addition to atrioventricular reciprocating tachycardia. Thirteen fetuses showed AFl during the fetal magnetocardiography session, including 4 that presented prior to the third trimester.

Indices and detectors for fetal MCG actography.

Several recent studies have demonstrated the usefulness of fetal magnetocardiogram (fMCG) actography, a relatively new method of detecting fetal movement that can be performed in conjunction with fMCG assessment of fetal heart rate and rhythm. In this study, we formulate indices of fetal activity that incorporate information from all channels to achieve improved sensitivity. We also utilize statistical detection to provide an objective means of inferring significant fetal activity.

Independent component analysis of normal and abnormal rhythm in twin pregnancies.

We investigated the utility of ICA for evaluation of fetal rhythm in five uncomplicated twin pregnancies and in five twin pregnancies complicated by fetal arrhythmia. Using objective and subjective criteria, we sought to determine how the signal-to-noise ratio, signal fidelity and interference rejection are affected when synthesizing the fetal signal using all the signal-containing ICA components (rank-p ICA) versus using the single dominant component (rank-1 ICA). The signal of each fetus was most commonly distributed over 1 or 2 ICA components, as previously observed in studies of singleton pregnancies; however, in 8 of 26 (31%) cases the signal of each fetus was distributed over 3, 4 or even 5 ICA components.

Matched-filter template generation via spatial filtering: application to fetal biomagnetic recordings.

We have developed a two-step procedure for signal processing of fetal biomagnetic recordings that removes cardiac interference and noise. First, a modified matched filter (MF) is applied to remove maternal cardiac interference; then, a simple signal space projection (SSP) is applied to remove noise. The key difference between our MF and a conventional one is that the interference template and the template scaling are derived from a signal that has been spatially filtered to isolate the interference, rather than from the raw signal.