Pearls of Knowledge: Sinus Dysrhythmia
Wednesday, December 03, 2025
Rhythm Interpretation: Sinus Dysrhythmia
Pearls of Knowledge © BrainyNurses.com
Sinus dysrhythmia originates in the SA node and discharges at irregular intervals. The heart rate will vary by more than 0.12 seconds which is considered a normal rate variation in sinus rhythm. The rhythm may be “normal” with heart rates between 60-100 beats per minute. Most frequently, it is associated with sinus bradycardia.
Sinus dysrhythmia is a normal phenomenon and is frequently associated with the respiratory pattern. The heart rate increases with inspiration and decreases with expiration due to increased intrathoracic pressure and reduced venous return with inspiration.
When sinus dysrhythmia occurs in the elderly, it is usually not related to the respiratory cycle and may be a precursor to sick sinus syndrome. It may also occur in digoxin toxicity.
Rhythm Analysis
(Heart rate varies by more than 0.12 seconds, which is 3 blocks.)
Summary
Sinus dysrhythmia is frequently seen but should have some degree of suspicion when it occurs in the elderly and the potential for dysfunction of the SA node. It may also be present in third-degree AV block and result in the irregular discharge of the P waves.
To enhance care provided for cardiac patients, check out Comprehensive Rhythm Review and Clinical Application. It is on-line, on-demand, with voice-over-power-point. The extensive handout is easy to follow and includes our “In My Pocket” cards as a ready reference tool.
