Sick sinus syndrome


Sick sinus syndrome, also known as sinus node dysfunction or sinus node disease, is a type of heart rhythm disorder. It affects the sinus node, the heart’s natural pacemaker that regulates heartbeat. Slow heartbeats, pauses (large intervals between heartbeats), or irregular heartbeats (arrhythmias) are symptoms of sick sinus syndrome.

The sick sinus condition is comparatively rare, but the risk of developing sick sinus syndrome increase with age. A pacemaker must eventually be installed to maintain the heart beating regularly in many people with sick sinus syndrome condition.


Sick sinus syndrome can occur without symptoms, and they can suddenly develop and resolve abruptly. Sick sinus syndrome symptoms and signs can include:

  • feeling of fluttering or fast heartbeats (palpitations)
  • fainting or feeling on the verge of fainting
  • slower heartbeat (bradycardia)
  • confusion
  • chest pain or discomfort
  • dizziness or lightheadedness
  • exhaustion
  • shortness of breath

If you experience any sick sinus syndrome signs or symptoms, consult your doctor. These issues can be brought on by a variety of medical diseases. It’s crucial to receive a prompt and precise diagnosis.

Call for emergency medical help immediately if you experience sudden or unexplained chest discomfort or believe you are suffering a heart attack.


The heart consists out of four chambers, two upper chambers called the atria and two lower chambers called the ventricles. The sinus node is located around the upper right chamber, or the atrium, acts as a natural pacemaker which controls the heart beats by sending electrical signals. When the atria receive these signals, the heart muscles start to contract and pump blood into the ventricles.

The heart signals will continue to go down to the atrioventricular (AV) node, where they slow down to allow blood to fill the ventricles. After that, the ventricles will contract to pump blood to the lungs or to rest of the body.

A healthy heart will have this process running smoothly, with a resting heart rate of 60-100 beats per minute.

Electrical signals are paced erratically in sick sinus syndrome. The heartbeat may be irregular, too rapid or too slow, or it may be interrupted by extended pauses. Although it is not very prevalent, the risk of acquiring sick sinus syndrome increases with age.

Sick sinus node syndrome can have various causes, such as:

  • The deterioration of cardiac tissues with aging
  • Sinus node damage or scarring following cardiac surgery
  • Heart disease
  • Inflammatory diseases that affect the heart
  • Medications to manage high blood pressure, such as beta blockers and calcium channel blockers
  • Medications to treat irregular heartbeats (arrhythmias)
  • Some Alzheimer’s disease medications
  • Having muscular dystrophy which is a neuromuscular disease
  • Obstructive sleep apnea
  • Uncommon genetic changes

Sick sinus syndrome has the following characteristics:

  • Sinus bradycardia. A slow heartbeat that is produced by the sinus node.
  • Sinus arrest. Beats are skipped as a result of a pause in sinus node’s signals.
  • Sinoatrial exit block. Pauses or skipped beats result from slower or obstructed signals to the upper heart chambers.
  • Chronotropic incompetence. At rest, the heart rate is within normal limits, but it doesn’t rise as high as it should with physical activity.
  • Tachycardia-bradycardia syndrome. The heartbeats are spaced out widely and alternate between rhythms that are unusually slow and fast.

Risk factors

At any age, sick sinus syndrome can develop. Most people in their 70s or older seem to have it. Sick sinus syndrome development can be increased due to heart disease’s common risk factors. Heart disease risk factors include:

  • Being overweight
  • Not enough exercise
  • High blood pressure
  • Increased cholesterol