[Initial heart rate variability and radiosensitivity in rabbits]

Area of Science:

• Radiology and Radiation Oncology
• Cardiology
• Autonomic Nervous System Physiology

Background:

• Radiosensitivity varies among individuals.
• The autonomic nervous system (ANS) influences physiological responses.
• Heart rate variability (HRV) parameters reflect ANS activity.

Purpose of the Study:

• To investigate the relationship between initial autonomic nervous system (ANS) functional state and radiosensitivity in rabbits.
• To assess how heart rate variability (HRV) parameters predict radiosensitivity after X-irradiation.

Main Methods:

• Total X-irradiation of rabbits at 2 Gy and 12 Gy doses.
• Analysis of time-frequency parameters of heart rate variability (HRV).
• Assessment of survival rates and rhythm-cardiologic correlates.

Main Results:

• Sympathotonic rabbits (adrenergic dominance) exhibited significantly higher radiosensitivity than vagotonic rabbits (parasympathetic dominance).
• Lower initial total power (TP) of HRV, indicating reduced regulatory influences on heart rhythm, correlated with higher radiosensitivity.
• Irradiation caused a sharp, irreversible suppression of TP in sympathicotonics at 12 Gy, leading to shorter lifespans (10.3 days vs. 18.8 days for vagotonics).
• Vagotonics showed a temporary TP suppression at 2 Gy with a subsequent rebound, suggesting greater resilience.

Conclusions:

• Initial autonomic nervous system (ANS) balance, reflected by heart rate variability (HRV) total power, is a key determinant of radiosensitivity.
• Low initial total power of HRV is a reliable marker for increased radiosensitivity.
• Understanding ANS-mediated radiosensitivity can inform radiation therapy strategies.