A Heart Condition Called Sick Sinus Syndrome

By Eva Briggs, M.D.

Recently one of my friends, who is in her 80s, relayed the following story. She was standing, talking to her husband, and suddenly passed out. She woke up to EMT’s who had placed a breathing assist mask over her face and electrodes on her chest. An ambulance transported her to the hospital. A workup revealed a disorder called sick sinus syndrome (SSS). By the time this article is published she will have received a pacemaker.

Your heart beats regularly because it contains a cluster of cells called the sinus node. It’s located in the right upper chamber (atrium). When healthy, it sends regular electrical signals to control the heart’s rhythm and rate. It slows down or speeds up as needed in response to changes in demand, such as exercise or temperature.

A normal functioning sinus node produces an orderly heartbeat — just as a conductor keeps the entire orchestra working smoothly together. A sick sinus node can lead to chaos. The heart might beat too slowly, called bradycardia. It might beat too fast, which is tachycardia. The rhythm can bounce between too fast and too slow: tachy-brady syndrome. The sinus node might pause, leading to long delay between heartbeats. Heartbeats might be skipped. The heart rate might be normal at rest, but unable to speed up with activity. It’s like an orchestra with an impaired conductor or no conductor at all.

One extreme symptom of SSS, which my friend experienced, is fainting. A very slow, erratic, or inefficient heartbeat doesn’t send sufficient blood to the brain. Lack of blood to the brain could also cause confusion. Other SSS symptoms include palpitations, exercise intolerance, fatigue, shortness of breath, chest pain or chest pressure.

Often SSS arises from age-related wear and tear to the heart. The disorder is most common in people in their 70s or older. Other causes include coronary artery disease, damage to the sinus node from heart surgery, certain medications, neuromuscular disease such as muscular dystrophy, obstructive sleep apnea and rarely,  genetic disorders.

Risk factors for heart disease also increase the risk of SSS.  These include high blood pressure, elevated cholesterol, obesity, sedentary lifestyle, and smoking.

Various tests of the heart’s electrical activity help make the diagnosis. An EKG gives a snapshot of the heart’s electrical activity, providing information about rate, rhythm and the conduction of electricity through the heart. Sometimes a longer period of observation is needed to establish the diagnosis. A Holter monitor automatically records heart activity for 24 –72 hours. The patient keeps a diary of symptoms to determine how they correlate with the heart’s electrical picture. An event recorder can be worn for a month. When a patient senses an irregular heartbeat, they press a button to capture the electrical picture at that moment. An implantable loop recorder is a small EKG device implanted just under the skin of the chest. It allows long term monitoring which is especially helpful for people who have infrequent symptoms.

Medicines to treat SSS target the heart rate to reduce risk for excessively rapid heartbeat. If SSS is associated with the abnormal rhythm called atrial fibrillation, blood thinners are often added to reduce stroke risk.

Many people, like my fainting friend, need a pacemaker to control their rhythm. This implantable device sends regular electrical impulses to the heart muscle. If the pacemaker doesn’t sufficiently control the heartrate, some patients need a surgery called cardiac ablation. This uses heat or cold to create tiny scars which block abnormally rapid rhythms.

Sick sinus syndrome affects about one out of every 600 people over age 65. It’s the most common reason for pacemaker insertion.