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.

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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Sick sinus syndrome occurs most often in people over the age of 50. Though uncommon, medical professionals do not consider it a rare condition. A variety of factors can cause sick sinus syndrome, including coronary artery disease, high blood pressure, and problems with the mitral or aortic valve, though many people have these problems and never develop the condition. Other possible causes include scar tissue from previous heart surgery and certain medications. Children who had atrial surgery can alsodevelop sick sinus syndrome.

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Genetics is not a common cause of sick sinus syndrome, but there are some links. Researches identified several genes that affect cardiac function. Genetic mutations that either reduce the flow of ions through the SA node, affecting its ability to properly send electrical signals, or alter the heart's ability to contract can lead to the condition.

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Most of the time, people with sick sinus rhythm do not have symptoms, and those that do occur often mimic other disorders. Some of these include chest pain, confusion, fainting, fatigue, dizziness, palpitations, memory problems, and shortness of breath. It is not uncommon for symptoms to come and go. Anyone experiencing these symptoms without a clear cause should talk to their doctor, as they may indicate a serious medical condition.

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Because symptoms of sick sinus syndrome mimic other health conditions, a doctor will likely run several diagnostic tests to confirm. An electrocardiogram (ECG) is the most common leads attached to the chest record the rhythm of the heartbeat. Abnormalities will often show up on an EKG tracing, although the changes may be variable and come and go. Doctors may also recommend event recorders or Holter monitors to track cardiac activity over a longer period. Another common test doctors order to assess heart function is an echocardiogram, which uses ultrasound technology to look at the structure and function of the heart.

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People with sick sinus rhythm who are asymptomatic may not need treatment other than monitoring for changes. People who display symptoms and are taking medication known for causing the condition may require alternative prescriptions. Because the heart beats abnormally in this condition, there is an increased risk of blood clots, so a doctor will often prescribe blood thinners as a preventative measure.

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Most people will eventually need a pacemaker to control the arrhythmias caused by sick sinus syndrome, and almost half of all pacemaker placement is related to this condition. The pacemaker is implanted under the skin in the chest and stimulates the heart to maintain a regular rhythm. The type of arrhythmia the person experiences determines the type of pacemaker they require.

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Additional Treatments

Some people with sick sinus syndrome require other treatments. If someone is still experiencing tachycardia after receiving a pacemaker, the doctor may prescribe anti-arrhythmia medication. The individual may also need AV node ablation. The AV node sits between the atria and the ventricles. Ablation destroys the tissue around the node, which prevents tachycardic rhythms from reaching the ventricles. Radiofrequency ablation can also prevent atrial fibrillation.

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Sick sinus syndrome usually worsens over time, which is why monitoring is so important, even when the person is asymptomatic. Arrhythmias can lead to complications including chest pain, clots, and fainting leading to falls and injuries. Heart failure is also possible, along with impaired blood flow to other organs, which could cause significant damage.

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Although sick sinus syndrome progresses and worsens over time, the outlook is good for those with a permanent pacemaker. The condition is not always preventable, but maintaining a healthy lifestyle can help. People at risk can stop smoking, maintain a healthy weight, exercise regularly, and keep blood pressure and cholesterol under control to minimize their chances of developing problems.

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