Fractal analysis: a new method for evaluating fetal heart rate variability

Area of Science:

• Cardiology
• Obstetrics
• Nonlinear Dynamics

Background:

• Fetal cardiotocography (CTG) is crucial for monitoring fetal well-being.
• Traditional CTG analysis can be subjective and may miss subtle abnormalities.
• Deterministic chaos and fractal analysis offer novel quantitative approaches to signal assessment.

Purpose of the Study:

• To apply deterministic chaos techniques, specifically fractal analysis (correlation dimension D2) and recurrence plots, to fetal CTG signals.
• To investigate the potential of these methods in distinguishing between normal and pathological fetal heart rate patterns.
• To explore the real-time application of recurrence plots for non-stationary CTG signals.

Main Methods:

• Analysis of fetal cardiotocography (CTG) tracings using "deterministic chaos" techniques.
• Evaluation of correlation dimension (D2) and graphic analysis of attractors to visualize the system's phase-space.
• Application of recurrence plots for real-time analysis of non-stationary signals.
• Comparison of results from expert and computerized CTG classification.

Main Results:

• Normal term CTG traces (37-41 weeks) exhibited a fractal dimension (D2) index between 4.22 and 5.22.
• Highly pathological CTG tracings showed a significantly lower D2 index, ranging from 2.0 to 3.09.
• Recurrence plots were introduced as a tool for real-time evaluation of non-stationary fetal heart rate signals.

Conclusions:

• Deterministic chaos analysis, particularly fractal dimension, can effectively differentiate normal from pathological fetal heart rate patterns.
• Recurrence plots offer a promising tool for real-time, non-stationary signal analysis in fetal heart rate monitoring.
• This study represents an early application of fractal analysis and recurrence plots to fetal heart rate evaluation using small datasets.