Cardiology Teaching Package
A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias
Sinus Arrhythmia
Sinus Arrhythmia, or "regularly irregular" sinus rhythm, is a variation on sinus rhythm where the P-P interval ( the distance between consecutive P waves) varies by more than 10%.
It can be naturally occurring or due to heart damage.
Causes can be:
- Respiratory-where the P-P interval lengthens and shortens with inspiration and expiration.
- Non-respiratory - where the process occurs seemingly for no reason.
- Sometimes seen in association with Complete Heart Block.
There are two examples below of sinus arrhythmia. The first is less obvious than the second.
Image: Sinus Arrhythmia Example 1
Image: Sinus Arrhythmia Example 2
Sinus arrhythmia is not commonly seen but the same evaluation procedure is used:
- Is there a P wave?
- Is each P wave the same shape?
- Is each P wave followed by a QRS complex?
- Is the P-R interval between 3-5 small squares?
- Is the rhythm regular?
If the answer to the first four questions is "yes", but the answer to the last is "no" then you have sinus arrhythmia.
