Sick sinus syndrome is a group of arrhythmias caused by problems with the heart's natural pacemaker, the sinoatrial (SA) node. Doctors may also call this condition sinus node dysfunction or sinus node disease. The resulting arrhythmias cause the heart to beat too fast, too slow, or irregularly. Although the disorder affects only one in 600 patients with heart disease, the chance of getting it increases with age. Many people who develop sick sinus syndrome end up needing a pacemaker.


1. Sinoatrial Node

The sinoatrial, sinus, or SA node keeps the heart beating regularly. It is located in the wall of the right atrium, one of the top chambers of the heart. Normally, the SA node sends a steady pace of electrical signals through the heart, maintaining a steady pace and rhythm. In sick sinus syndrome, these signals are abnormal. The possible resulting arrhythmias include bradycardia (slow heart rate), tachycardia (fast heart rate), or both. The heart may also briefly pause or stop beating.

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