What is the Origin of Respiratory Sinus Arrhythmia?

The term is derived from cardiology and respiratory physiology, where arrhythmia simply means a variation in heart rhythm, and sinus refers to the heart's natural pacemaker, the sinoatrial node. The phenomenon has been known for centuries, but its clinical significance as a measure of autonomic balance gained prominence with the advent of heart rate variability (HRV) analysis in the late 20th century.

What is the Mechanism of Respiratory Sinus Arrhythmia?

During inhalation, the increased stretch of the lungs transiently inhibits the vagus nerve, leading to a slight sympathetic dominance and an increase in heart rate. Conversely, the pause or exhalation phase removes this inhibition, allowing the vagus nerve to reassert its influence, which releases acetylcholine and slows the heart rate. This constant, rhythmic modulation demonstrates the heart's high responsiveness to autonomic input. A high RSA indicates that the parasympathetic "brake" is strong and capable of rapidly counteracting sympathetic activity, thereby optimizing the body's neuro-hormonal regulation.

Respiratory Sinus Arrhythmia ∞ Area

Respiratory Sinus Arrhythmia

Meaning

Respiratory Sinus Arrhythmia (RSA) is a natural, healthy fluctuation in heart rate that is synchronized with the phases of respiration, where the heart rate increases during inhalation and decreases during exhalation. This physiological phenomenon is a direct, non-invasive measure of vagal tone and the functional integrity of the parasympathetic nervous system. A high-amplitude RSA indicates a robust and flexible autonomic nervous system, which is a key biomarker for stress resilience and overall hormonal health. Conversely, a reduced RSA suggests a system dominated by sympathetic drive and chronic stress.