Respiratory Sinus Arrhythmia (RSA) is defined as a slight variation in the regularity of a sinus rhythm, usually one that exceeds 0.12 seconds between the longest and shortest cycles.
RSA is a normal and benign finding in children and young adults, and tends to diminish or disappear with age.
RSA occurs primarily through respiratory influence on the vagal nerve.
RSA is becomes more apparent with slower heart rates, As the heart rate increases the vagal influence tends to decrease.
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