Sick sinus syndrome is an umbrella term that covers three heart rhythm problems (arrhythmias):
sinus bradycardia, which causes a slow heart rate
tachycardias, which cause fast heart rates, often followed by a very slow heart rate. Types of tachycardias include atrial fibrillation, atrial flutter/tachycardia, and supraventricular tachycardia
bradycardia-tachycardia, which causes alternating slow and fast heart rhythms
A problem with a part of the heart called the sinus node causes these arrhythmias. This group of specialized cells in the upper right chamber of the heart controls the heart's rhythm by sending electrical signals that tell the heart to beat. In someone with sick sinus syndrome, these signals do not come at a steady pace.
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