Sick sinus syndrome

Alternative names

Bradycardia-tachycardia syndrome

Definition

Sick sinus syndrome is a group of abnormal heartbeats (arrhythmias) presumably caused by a malfunction of the sinus node, the heart's "natural" pacemaker.

Causes, incidence, and risk factors

Sick sinus syndrome is a relatively uncommon syndrome. It can result in many abnormal heart rhthyms (arrhythmias), including sinus arrest, sinus node exit block, sinus bradycardia, and other other types of bradycardia (slow heart rate).

Sick sinus syndrome may also be associated with tachycardias (fast heart rate) such as PSVT and atrial fibrillation. Tachycardias that occur with sick sinus syndrome are characterized by a long pause after the tachycardia.

Abnormal rhythms are often caused or worsened by medications such as digitalis, calcium channel blockers, beta-blockers, sympatholytic medications, and anti-arrhythmics. Disorders that cause scarring, degeneration, or damage to the conduction system can cause sick sinus syndrome, including sarcoidosis, amyloidosis, Chagas' disease, and cardiomyopathies.

Sick sinus syndrome is more common in elderly adults, where the cause is often a non-specific, scar-like degeneration of the conduction system. Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children.

Coronary artery disease, high blood pressure, and aortic and mitral valve diseases may be associated with sick sinus syndrome, although this association may only be incidental.

Symptoms

• fainting or near fainting
  
• dizziness or light-headedness
  
• confusion
  
• sensation of feeling heart beat (palpitations)
  
• chest pain or angina
  
• shortness of breath
  
• fatigue
  

Note: Usually no symptoms are present.

Signs and tests

The symptoms are non-specific and may mimic other disorders. The patient's heart rate may be very slow at any time or after termination of an episode of tachycardia. Blood pressure may be normal or low.

Sick sinus syndrome may cause symptoms of heart failure to occur or worsen. The diagnosis of sick sinus syndrome includes a history of symptoms that occur only during episodes of arrhythmia. However, this correlation often is difficult to prove.

An ECG would show various arrhythmias characteristic of sick sinus syndrome. Holter monitoring may be needed to document the arrhythmia because of the episodic nature of the disorder. An EPS (intracardiac electrophysiology study) may confirm that the arrhythmia is caused by a disorder of the sinus node.