A healthy heartbeat is not completely regular. The intervals are affected by breathing, hormonal reactions, metabolic processes, stress, cognitive activity and other influences of the autonomic nervous system. “This so-called heart rate variability (HRV) is a sign of physical and mental vitality and flexibility. If the HRV is low, i.e. the heart beats too evenly as is the case with people suffering from depression, it is a sign that there is a disturbance in communication between the heart and the brain,” explains Andreas Schwerdtfeger, health psychologist at the University of Graz. In a recent publication in the specialist journal Clinical Neurophysiology, he and colleagues from the Graz University of Technology, the Medical University of Graz, the University of Ulm and the University of California, Irvine summarised the current state of research on HRV. Their findings unlock new diagnostic and therapeutic possibilities.
Due to the close ties to structures of the central nervous system, the HRV can provide information about communication between the heart and the brain. Based on clinical findings, the authors show that heart rate variability can be used in high-end medicine to help evaluate various situations such as when premature babies require intensive therapy, patients have had a heart transplantation, people are on artificial respiration or suffer brain death. “HRV can be used to determine whether and to what extent the connection between the heart and the brain is disturbed,” say Gert Pfurtscheller (Graz University of Technology) and clinical cooperation partners Gerhard Schwarz and Klaus Pfurtscheller (Medical University of Graz). In this context, Schwarz considers the “rigidity of variability” of coma patients and Klaus Pfurtscheller the monitoring of HRV in preterm infants to be particularly relevant.
The publication also discusses current imaging findings of functional magnetic resonance imaging for heart-brain interaction and for identifying central nervous pacemakers of HRV. “Not only can a pacemaker in the brain synchronise different slow body rhythms such as blood pressure waves, heart rate and respiration and thus optimise energy requirements, it can also increase heart rate variability,” says Gert Pfurtscheller, retired professor of medical informatics, who evaluated most of the magnetic resonance data.
Conversely, an increase in the HRV also leads to changes in the brain. Schwerdtfeger, who has investigated the psychological relationships and therapeutic possibilities of HRV, knows: “When we control the breathing, we can improve the heart rate variability and thus physical and psychological well-being.” Six breaths per minute, i.e. one cycle every ten seconds, provide for an optimal oxygen supply to the brain. “This technique not only reduces anxiety, it may also improve brain functions such as working memory and reaction time,” reports the psychologist.
Publication
Schwerdtfeger, A. R., Schwarz, G., Pfurtscheller, K., Thayer, J. F., Jarczok, M. N. & Pfurtscheller, G. (2019)
Invited review: Heart rate variability (HRV): From brain death to resonance breathing at 6 breaths/minute
Clinical Neurophysiology