[Fractal analysis and arterial hypertension]

Area of Science:

• Cardiovascular Physiology
• Complexity Science
• Biomedical Engineering

Background:

• Fractal analysis offers insights into cardiovascular variability and regulatory mechanisms.
• Homeostasis is associated with optimal complexity (beta coefficient ≈ 1), while pathology shows altered complexity (beta coefficient ≠ 1).

Purpose of the Study:

• To investigate if hypertension is associated with alterations in the fractal component of blood pressure (BP) and heart rate (HR) variability.
• To determine the relationship between fractal complexity, hypertension severity, and baroreflex sensitivity.

Main Methods:

• Eighty-eight hypertensive subjects underwent 24-hour ambulatory BP monitoring and 30-minute beat-to-beat BP/HR recordings at rest.
• Fractal analysis using coarse-graining spectral analysis was applied to BP and RR interval time series to calculate the beta coefficient.
• Spontaneous baroreflex sensitivity was assessed using the method of sequences.

Main Results:

• The fractal percentage in BP and HR signals remained stable with increasing hypertension severity.
• A weak correlation was found between the RR interval beta coefficient and ambulatory BP, but no correlation existed between BP beta coefficient and ambulatory BP.
• The RR interval beta coefficient significantly correlated with spontaneous baroreflex sensitivity (r = -0.59, p < 0.0001).

Conclusions:

• Hypertension appears to alter the complexity of HR variability more than BP variability, suggesting impaired regulatory processes.
• The correlation between baroreflex gain and RR interval beta coefficient may indicate altered parasympathetic nervous system activity.
• These findings highlight the role of HR variability and cardiac output in the pathophysiology of hypertension.