Your heart typically beats 60 to 100 times per minute, thanks to the sinus node, your body’s natural pacemaker located in the right upper chamber of the heart.
“The sinus node initiates an electrical signal that tells the heart to contract,” says UNC cardiologist Christopher Kelly, MD. “Most of the time, that system works well, but for some people, the electrical system breaks down.”
This breakdown is called sick sinus syndrome. Dr. Kelly explains what to know about this condition.
Sick Sinus Syndrome and Heart Rhythm
Sick sinus syndrome occurs when the sinus node stops sending its regular signal to the heart. As a result, the heart rhythm is affected. Typically, the heartbeat slows dramatically (bradycardia) or becomes irregular. Occasionally, the heartbeat can alternate between slow and fast rhythms (tachy-brady syndrome).
“The heart has a backup system in place,” Dr. Kelly says. “There are other pacemakers in the heart to help it beat, but they aren’t as reliable as the sinus node.”
Age is the biggest risk factor for sick sinus syndrome.
Medications for other heart conditions can sometimes affect the sinus node. Beta blockers, for example, are meant to slow the heart rate to prevent arrhythmias (irregular heartbeats), but one possible side effect is a problematic decrease in the heart rate.
The condition is uncommon, affecting 1 in 1,000 people; in people older than 65, the rate is 1 in 600.
Sick Sinus Syndrome Symptoms and Diagnosis
When the sinus node doesn’t send its electrical signal for a heartbeat, the heart rate slows and affects blood flow throughout the body. This can cause fatigue and sluggishness. Blood pressure can also drop dramatically, causing lightheadedness or loss of consciousness. During exercise, people may experience chest pain or have difficulty breathing.
“People tend to feel slow, tired and unable to exert themselves,” Dr. Kelly says. “With any of these symptoms, there is a list of possible conditions we have to consider.”
Doctors diagnose sick sinus syndrome with an electrocardiogram (EKG), which measures electrical signals from the heart.
Dr. Kelly notes that for many people, symptoms of sinus dysfunction aren’t always present or continuous. If an initial EKG is normal but the person is still experiencing symptoms, a physician may use a cardiac event monitor, a wearable EKG, to see how the heart’s electrical system works over the course of a month.
Sick Sinus Syndrome Treatment
If it’s clear that the sinus node dysfunction is the result of medication, the condition can be treated by reducing or discontinuing the medication. Otherwise, most people with sick sinus syndrome will require a pacemaker for the rest of their lives.
A pacemaker takes over for the sinus node by generating the electrical impulse that causes the heart to beat. It is typically inserted in the left shoulder and includes wires that lead to the heart. Those lines monitor the heart for electrical activity.
“If the heart is beating normally, the pacemaker is in standby,” Dr. Kelly says. “If there is no electrical activity, the pacemaker will generate the electric activity needed for the heart to beat on schedule. Depending on the severity of the sick sinus syndrome, some people are completely dependent on the pacemaker, while others may need their pacemaker to generate that impulse only occasionally.”
Once the pacemaker is installed, a person’s activity levels can return to normal. Pacemakers require battery changes every eight to 12 years, depending on how frequently the pacemaker is working in place of the sinus node.
If you’re concerned about the health of your heart, talk to your doctor. If you need a doctor, find one near you.