, also called '''Bradycardia-tachycardia syndrome''' is a group of abnormal heartbeats (
Arrhythmia s) presumably caused by a malfunction of the
Sinus Node , the heart's "natural" pacemaker. '''Bradycardia-tachycardia syndrome''' is a variant of sick sinus syndrome where atrial flutter and fibrillation alternate with prolonged periods of
Asystole .
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 types of
Bradycardia (slow heart rate).
Sick sinus syndrome may also be associated with tachycardias (fast heart rate) such as
Paroxysmal Supraventricular Tachycardia (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 Blocker s,
Beta-blocker s, 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
Cardiac 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.
Even though many types of sick sinus syndrome produce no symptoms, patients may present with fainting or near fainting episodes, dizziness or light-headedness, palpitations, chest pain, shortness of breath, and
- Chest pain or Angina
- Shortness of breath
- Fatigue
Ambulatory monitoring of the
Electrocardiogram (ECG) may be necessary arrhythmias are transient. The ECG may show any of the folliwing
- Inappropriate sinus bradycardia
- Sinus arrest
- Sinoatrial block
- Atrial fibrillation with slow ventricular response
- A prolonged asystolic period after a periof of tachycardias
- Atrial flutter
- Ectopic atrial tachycardia
- Sinus node reentrant tachycardia
Electrophysiologic tests are no longer used for diagnostic purposes because of their low specificity and sensitivity. Cardioinhibitory and vasodepressor forms of sick sinus syndrome may be revealed by tilt table testing.
Bradyarrhythmias are well controlled with pacemakers, while tachyarrhytmias respond well to medical therapy. However, because both bradyarrhythmias and tachyarrhythmias may be present, drugs to control tachyarrhythmia may exacerbate bradyarrhythmia. Therefore, a pacemaker is implanted before drug therapy is begun for the tachyarrhythmia.
