Sick sinus syndrome (SSS) is a general term for a group of disorders caused by a malfunctioning sinus node. The sinus node acts as a pacemaker inside of the heart. Sinus rhythm (the normal beating of the heart) is controlled by electrical impulses from the sinus node. Without the correct impulses, the heart cannot beat properly.
There are multiple disorders that occur when the sinus node does not work properly. The resulting heart beat or rhythm will be different depending on the specific electrical activity at the sinus node.
The disorders that characterize SSS include:
- sinus bradycardia: the heart beats very slowly, less than 60 beats per minute
- sinus arrest or sinus pause: the sinus node temporarily stops working or pauses, causing a change in the heart’s beating
- sinoatrial block: the sinus node impulse is blocked from reaching the atria, the two upper chambers of the heart
- tachycardia-bradycardia (or tachy-brady) syndrome: the heart alternates between a very slow and very fast beat
The risk of developing SSS increases with age. Having SSS at birth is called congenital sick sinus syndrome. Congenital heart conditions are the main cause of SSS in young children and adults.
Risk factors for SSS include:
- history of congenital heart disease (even with repairs, the heart is still weak)
- thyroid disease history
- sleep apnea disorder
- coronary artery disease: the coronary artery becomes clogged, and blood flow to the heart is restricted
SSS may be caused by a number of factors, including:
- damage or scarring of the heart’s electric system, caused by a disease or other health condition
- scar tissue from a past heart surgery
- certain medications, such as calcium channel blockers or beta blockers used to treat high blood pressure, heart disease, and other conditions
- the breakdown of heart muscle due to age, which is the most common risk factor
The widely held belief is that the condition is linked to the breakdown of heart muscle cells. The breakdown of these cells causes a change in the system that sends electrical impulses through the heart. The sinus node begins to malfunction as a result, and the heart cannot beat normally.
Patients with SSS often display no symptoms. However, when the heart becomes compromised and cannot pump an adequate amount of blood, symptoms quickly become apparent.
Symptoms of SSS include:
- fainting or fainting sensations
- palpitations (abnormal heart beats)
- very slow pulse (bradycardia)
- difficulty breathing
- chest pain
- mental confusion
- memory problems
- disrupted sleep
It’s important to see your doctor immediately if you experience the following symptoms, especially if you have a personal or family history of heart disease. These could be symptoms of a heart attack or early cardiac arrest. Symptoms include:
- chest pain
- difficulty breathing
- profuse sweating
- pain or discomfort in the upper body
- mental confusion or panics
- abdominal pain
See your doctor as soon as possible if you’re experiencing any symptoms of SSS.
Diagnosing SSS can be difficult. You may have no symptoms or family history of heart disease. Your doctor must rely on tests that measure the function of your heart to make a diagnosis. These tests include:
- An electrocardiogram (ECG), which is a test that records the electrical activity of the heart.
- An echocardiogram, which is an ultrasonic imaging test of the heart.
- A transesophageal echocardiogram (TEE), which is a test where a special ultrasound device is put down the patient’s throat and into the esophagus to get a clear image of the heart size, the contracting strength of the heart, and any damage to the heart muscle.
- A holter monitoring, which is a test where an electrocardiogram monitor is attached to the chest and worn for at least one 24-hour period. The patient keeps a diary of his or her activities and symptoms while wearing the monitor.
Treatment for mild or early cases of SSS involves relieving symptoms. Your doctors may adjust or change your medication if that is the problem. They may also prescribe additional medications that may have a direct effect on heart rhythm. Eventually, however, most people with SSS will need an artificial pacemaker implant when the sinus node is no longer able to adequately perform.
A pacemaker is a very small machine that is surgically implanted in the chest or abdomen to regulate your heartbeat. It does this through sending electrical pulses to the heart.
Almost one-half of pacemaker implantations are performed because of problems related to sick sinus syndrome. Pacemakers are generally tolerated well, and most people experience few complications.
Rare complications of a pacemaker implant include:
- myocardial perforation (accidental hole made in the heart during surgery)
- infection from the implant (bacteria brought in during surgery causes infection)
- venous thrombosis (blood clot within the body’s veins)
- collapsed lung
With modern technology, there is a growing interest in creating a biological pacemaker. This could be done by taking cells containing pace-making genes and implanting them in the heart. The cells would then grow into the heart and become a new pacemaker.
A second approach would be to use stem cells. Stem cells are immature cells capable of developing into any specific type of mature cell. The cells could potentially grow into the same type of heart tissue as the sinus node.
Improvements in pacemaker technology have greatly helped the outlook for SSS. Pacemakers provide the missing electrical impulses from a defective sinus node. Pacemakers are not a cure, but they are a very effective treatment.
The outlooks for those who cannot or do not undergo treatment are more uncertain. A heart that beats irregularly is more susceptible to cardiac arrest, which can cause sudden death. Untreated SSS may also lead to heart failure. People with untreated bradycardia-tachycardia syndrome are at greater risk for blood clots and stroke.