Assessment of fetal growth on the basis of signal strength in fetal magnetocardiography.

Fetal magnetocardiography has shown that fetal P wave and QRS complex durations increase with gestational age, reflecting change in cardiac muscle mass. The latter should, in principle, be associated with an increase in signal strength. We examined two approaches for determining QRS signal strength in a healthy fetus on a weekly basis in the second and third trimester.

Fetal magnetocardiography: time intervals and heart rate variability.

Biomagnetism in the perinatal domain has been dominated by fetal cardiology, and early work pointed out the potential of both fetal cardiac time intervals (CTI) and heart rate variability (HRV) for future clinical applications. Recent improvements in instrumentation have permitted numerous groups to investigate a substantial number of healthy fetuses in these two areas and to lay the groundwork for a delineation of normal ranges. With respect to fetal CTI it is now clear that in particular the duration of P wave, PR interval and QRS complex reflect fetal growth and development.

Finite volume analysis of temperature effects induced by active MRI implants with cylindrical symmetry: 1. Properly working devices.

Background: Active Magnetic Resonance Imaging implants are constructed as resonators tuned to the Larmor frequency of a magnetic resonance system with a specific field strength. The resonating circuit may be embedded into or added to the normal metallic implant structure. The resonators build inductively coupled wireless transmit and receive coils and can amplify the signal, normally decreased by eddy currents, inside metallic structures without affecting the rest of the spin ensemble.

Dependency of magnetocardiographically determined fetal cardiac time intervals on gestational age, gender and postnatal biometrics in healthy pregnancies.

BACKGROUND: Magnetocardiography enables the precise determination of fetal cardiac time intervals (CTI) as early as the second trimester of pregnancy. It has been shown that fetal CTI change in course of gestation. The aim of this work was to investigate the dependency of fetal CTI on gestational age, gender and postnatal biometric data in a substantial sample of subjects during normal pregnancy.

Changes in the frequency power spectrum of fetal heart rate in the course of pregnancy.

Objective: The aim of this study was to examine changes in the heart rate variability based on the frequency power spectrum of healthy fetuses during the second and third trimester of pregnancy.

Methods: We analyzed 222 fetal magnetocardiograms recorded in 49 healthy singleton pregnancies between the 16th and 42nd week. Discrete Fourier transformation was performed on the time-based step function of the RR-intervals.

Spatial distribution of repolarization times in patients with coronary artery disease.

The potential clinical value of QT dispersion (QTd), a measure of the interlead range of QT interval duration in the surface 12-lead ECG, remains ambiguous. The aim of the study was the temporal and spatial analysis of the QT interval in healthy subjects and in patients with coronary artery disease (CAD) using magnetocardiography (MCG) and surface ECG. Standard 12-lead ECG and 37-channel MCG were performed in 20 healthy subjects, 23 patients with CAD without prior myocardial infarction (MI), 31 MI patients and 11 MI patients with ventricular tachycardia (VT).

Is there evidence of fetal-maternal heart rate synchronization?

Background: The prenatal condition offers a unique possibility of examining physiological interaction between individuals. Goal of this work was to look for evidence of coordination between fetal and maternal cardiac systems.

Methods: 177 magnetocardiograms were recorded in 62 pregnancies (16th-42nd week of gestation).

Fetal heart rate variability and complexity in the course of pregnancy.

Aim of this study was the examination of fetal heart rate variability and complexity measures during pregnancy using fetal magnetocardiography. We registered 80 fetal magnetocardiograms in 19 healthy fetuses between the 16th and 41st week of gestation. On the basis of beat to beat intervals, mean RR interval (mRR), its standard deviation (SD), root mean square of successive differences (RMSSD), as well as complexity variables such as dimension (ApD1), entropy (ApEn), Lyapunov exponent (ApML) and trajectory divergence rate (p) were calculated for each recording.

Spatial distribution of QT intervals: an alternative approach to QT dispersion.

QT dispersion (QTd) describes the heterogeneity of ventricular repolarization on the basis of the temporal range of QT intervals as measured in the 12-lead ECG. We examined the spatial distribution of QTd using multichannel magnetocardiograms (MCGs), which noninvasively register changes in magnetic field strength at 37 sites over the heart. As in ECG, the MCG signal in each channel may be used to measure QT interval.