Heart rate features in fetal behavioural states

Area of Science:

• Cardiology
• Fetal Medicine
• Biomedical Engineering

Background:

• Fetal behavioral states are traditionally defined using cardiotocography (CTG) based on eye movements, body movements, and heart rate patterns.
• High-resolution fetal magnetocardiography (fMCG) offers a non-invasive method to assess fetal cardiac activity with beat-to-beat precision.

Purpose of the Study:

• To investigate if fetal behavioral states can be identified using only heart rate features from high-resolution fetal magnetocardiography.
• To determine the efficacy of specific heart rate variability measures in distinguishing between fetal behavioral states.

Main Methods:

• Magnetocardiograms were recorded from 40 healthy fetuses (36-41 weeks gestation) at a 1 kHz sampling rate.
• RR interval time series were analyzed using measures like mean RR interval, standard deviation of NN intervals (SDNN), root mean square of successive differences (RMSSD), and symbolic dynamics.
• Epochs corresponding to fetal behavioral states 1F, 2F, and 4F were identified and quantified.

Main Results:

• Significant differences were observed in all quantified heart rate measures between the different fetal behavioral states.
• Quadratic discriminant analysis demonstrated that mean RR interval and SDNN were sufficient for classifying fetal behavioral states with 92% accuracy.
• RMSSD and symbolic dynamics revealed potential for further insights into short-term heart rate variability within these states.

Conclusions:

• Heart rate measures, particularly those reflecting overall heart rate characteristics, can effectively differentiate between fetal behavioral states identified via RR interval time series.
• Analysis of short-term variability using RMSSD and symbolic dynamics may uncover novel aspects of fetal behavioral states.
• Fetal magnetocardiography provides a promising tool for non-invasively assessing fetal behavioral states through detailed heart rate analysis.