Pearls of Knowledge: Sick Sinus Syndrome
Wednesday, December 03, 2025
Rhythm Interpretation: Sick Sinus Syndrome
Pearls of Knowledge © BrainyNurses.com
Sick sinus syndrome is abnormal function of the SA node due of a wide range of abnormalities. Shifting of the pacing site within the SA node accounts for the changes in heart rate and P wave configurations which will be seen. In atrial fibrillation, damage to the AV node can also result in sick sinus syndrome.
Sick sinus syndrome is often known as “tachy-brady” syndrome. The slower the rate, the more symptomatic the patient will be. Atropine may be used if it is symptomatic bradycardia. Generally, a pacemaker will be inserted. Anticoagulation should be considered if a very marked tachy-brady syndrome as clots may form during the bradycardic episodes and be released with the tachycardic ones.
Rhythm Analysis
(Continuous rhythm strips)
• Begins as a sinus tachycardia, rate of 125 BPM.
• Slows to around 80 BPM on the second strip.
• The heart rate is the slowest on the fourth strip with a heart rate of 20 BPM.
• Note the ST segment depression and symmetrical T wave inversion indicative of ischemia with the slower rates.
Rhythm Analysis
(Continuous rhythm strips)
• Underlying rhythm is atrial fibrillation.
• Begins with a heart rate of 42-50 BPM in the initial strip.
• Increases to 125-150 BPM on the second strip and then slows at the end of the third strip.
• The changes in heart rate are due to AV nodal disease.
• Typically, atrial fibrillation will have a more consistent ventricular rate.
Summary
Sick sinus syndrome is more common with damage to the SA node but the AV node is also susceptible and in atrial fibrillation, that damage can present as a “tachy-brady” rhythm. Due to the damage to the conduction system, a permanent pacemaker will be considered.
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