Harvard Heart Letter

Another kind of heart rhythm problem

It's called "sick sinus syndrome" and could be the reason you are slowing down. Learn how to spot and treat this condition.

Contrary to what the name suggests, sick sinus syndrome has nothing to do with your nasal passages. Instead, the term encompasses a set of heartbeat irregularities that can cause fainting, weakness, palpitations, and shortness of breath.

How a heartbeat happens

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 you have an average heart rate of 60 beats per minute, the sinus node will send out an impulse approximately once per second," says Dr. Patrick Ellinor, a cardiologist and arrhythmia specialist at Harvard-affiliated Massachusetts General Hospital.

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