CARDIOVASCULAR NEURAL REGULATION EXPLORED IN THE FREQUENCY-DOMAIN

Heart period and arterial pressure short-term variabilities contain, in addition to cardiac cycle, two main rhythmic oscillations at approximately 0.1 Hz (low frequency) and 0.25 Hz (high frequency). The power and center frequency of these oscillations can be assessed with spectral analysis, which also provides a measure of total variability (i.e., variance). Human and experimental studies support the view that under stationary conditions, left frequency of RR variability is a broad marker of sympathetic activity, high frequency is a broad marker of vagal activity, and their ratio is an index of sympathovagal balance. This methodology might provide a new insight into cardiovascular neural regulation in health and disease.