What is sick sinus syndrome?
Each time your heart beats, a tiny jolt of electrical current triggers the heart muscle to contract. The stimulus is sent by the sinus node (also called the sinoatrial node), a cluster of cells in the upper right portion of your heart that acts as your body's natural pacemaker. If your heart rate is 60 beats per minute, the sinus node will send out an impulse approximately once per second.
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