Sinus arrhythmia is a commonly encountered variation of ''normal''

sinus rhythm A sinus rhythm is any cardiac rhythm in which depolarisation of the cardiac muscle begins at the sinus node. It is characterised by the presence of correctly oriented P waves on the electrocardiogram (ECG). Sinus rhythm is necessary, but not s ...

. Sinus arrhythmia characteristically presents with an irregular rate in which the variation in the R-R interval vary by more than 0.12 seconds (120 milliseconds). Additionally, P waves are typically mono-form and in a pattern consistent with atrial activation originating from the

sinus node The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of cells known as pacemaker cells. The sinus node is approxima ...

Respiratory sinus arrhythmia

During respiration, the intermittent

vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and righ ...

activation occurs, which results in beat to beat variations in the resting heart rate. During inspiration vagal tone is slowed down and the heart rate goes up (being maximal at the peak of inspiration), while during expiration vagal tone is increased and heart rate decreases, being slowest at end-inspiration. When present, respiratory sinus arrhythmia typically indicates good cardiovascular health and is more commonly seen in young healthy people, especially those with enhanced vagal tone or slower heart rates. CC-BY icon

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References

{{reflist Vagus nerve Cardiac electrophysiology Cardiac arrhythmia

Respiratory sinus arrhythmia

See also

References