Heart rate Variability and Health

Heart rate variability (HRV) is an indicator of whether the autonomic nervous system is functioning in a balanced manner. It also shows if the wake centers and brain stem communications are functioning properly.

The autonomic nervous system consists of two parts: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). The sympathetic system is the system that is active after an encountered or perceived stress. The stress causes cortisol and adrenaline secretion from the adrenal glands by the orders of hormones secreted by the brain (HPA axis). Blood pressure rises, breathing becomes more faster, heartbeats accelerate, and blood circulation is withdrawn from the internal organs and directed to the arms and legs; In order to allow us to cope (fight) or escape the stressing stimuli (flight). This is called the fight or flight stress response.

When the sympathetic system response terminates, the parasympathetic system kicks in. The heart rate slows down, blood pressure decreases, blood flow is redirected to internal organs, digestion begins, and wound healing and the immune system go into effect.

Normally or naturally, situations that lead to a fight or flight stress response occur rarely; like encountering a wild animal or enemies and natural disasters. But nowadays, due to modern living, big and small stresses show up continuously; our stress response is always active during our wake hours, and sometimes even when we are asleep. This chronic sympathetic stress response suppresses the parasympathetic system. Today’s urban populations living under daily chronic stress have a tendency for high heart rates, blood pressure and blood sugar levels.

Another cause of chronic stress response is having a history of childhood adversities. These traumas cause HPA axis dysfunction. Due to changes in the amygdalar structure and function, traumatized individuals give exaggerated stress responses to all encountered and/or perceived stresses. This causes a chronic stress response and sympathetic overdrive from childhood. The sympathetic overdrive leads to chronically fast heart rates. The heart works overtime by working without any rest throughout the day and night.
Under ideal or normal conditions, sympathetic and parasympathetic systems are under balance. The interval between each heartbeat is not fixed; the interval changes with every inhalation. This variability is normal and healthy.
However, in people who have sympathetic system dominance and whose parasympathetic system cannot take over, the heart works faster than normal and the fluctuations that accompany breathing are lost. This is called decreased heart rate variability. Patients with low heart rate variability are also inappropriately and overly responsive to small stressful stimuli; whereas, in individuals who are imperturbable and emotionally balanced under stress have high heart rate variability.

Patients with cardiovascular disease and cancer with decreased heart rate variability have low survival and recovery rates compared to patients with high heart rate variability.
Having low heart rate variability does not mean it has to stay that way. A person can learn to increase heart rate variability. The ideal heart rate variability occurs when a person is calm and emotionally relieved, and breathing 5 to 7 times per minute. During yoga practice, meditation, and breathing exercises, consciously taking slow, deep, long breaths engages the parasympathetic system. The parasympathetic system dominance first is seen during yoga and meditation practice times, with time and continued practice, becomes more active in time throughout the day (ie not practicing). Parasympathetic dominance leads to heart rate variability increases.

Increased heart rate variability leads to a decline in anxiety and depression findings, and an increase in the quality of life and well-being. Adding yoga, meditation and breathing exercises to treatments in addition to conventional medical treatments in trauma patients exposed to violence or abuse, depression and anxiety, in patients with high blood pressure and cardiac problems; accelerates the healing process and provides a better therapeutical response.