Heart rate variability (HRV): From brain death to resonance breathing at 6 breaths per minute.

Heart rate variability (HRV) has been associated with various diseases and reflects autonomic cardiac control sensitive to central nervous system function. Examples of the heart-brain interaction are illustrated by extreme clinical conditions such as brain death, orthotopic heart transplantation, weaning from respirator support, and brain maturation in preterm infants. Interactions with the immune system document the importance of HRV for tumor growth and prognosis. Research linking HRV to the regulation of negative emotions including depression and anxiety document the sensitive influence of central commands on cardiac activity. Moreover, 0.1 Hz oscillations in the heart and the brain seem to be coupled, thus indicating central pacemakers on the heart rhythm. Moreover, low frequency oscillations in heart rate seem to be composed of two subcomponents presumably signaling different central-autonomic functions. We conclude by showing that breathing at 6 breaths/minute could induce coherence of the 0.1 Hz oscillations, thus facilitating physical and psychological function. The reviewed findings impressively demonstrate that central nervous system function modifies the rhythm of the heart and vice versa, suggesting that HRV could be a useful indicator of central-autonomic integration and that 0.1 Hz oscillations play a major role in physical and mental health via optimizing energy supply.