Heart Rate Variability (HRV) is a measure of the variations in time intervals between consecutive heartbeats, reflecting the dynamic interplay between the sympathetic and parasympathetic branches of the autonomic nervous system. Beginning with an overview of the physiological basis of cardiac system, this master's thesis explores the most widespread technique to assess the heart rate variability, i.e., the ECG. Given that the patient data used to carry out the computational analysis derive from cancer patients, the research was carried out on the cardiac variability of people suffering from this disease and on new treatment option with exposure to low-energy amplitude-modulated radiofrequency electromagnetic fields.