Sick sinus syndrome

Alternative names:

bradycardia-tachycardia syndrome

Definition:

A group of abnormal heartbeats (arrythmias) presumably caused by malfunction of the sinus node, the "natural" heart pacemaker.

Causes, incidence, and risk factors:

Sick sinus syndrome is a relatively uncommon syndrome affecting approximately 3 out of 10,000 people. It can be manifested by many arrhythmias, including sinus arrest, sinus bradycardia, sinus node exit block, and other similar bradycardias (slow heart rates). Tachycardias (fast heart rate) such as PSVT and atrial fibrillation/flutter may also be associated with sick sinus syndrome. Tachycardias of sick sinus syndrome are characterized by a long pause following the ending of the tachycardia.

Abnormal rhythms are often caused or worsened by medications such as digitalis, calcium channel blockers, beta blockers, sympatholytic medications, and antiarrhythmics. Disorders that cause scarring, degeneration, or damage to the conduction system can cause sick sinus syndrome, including sarcoidosis, amyloidosis, Chagas' disease, and cardiomyopathies. Cardiac surgery, especially to the atria, is a common cause of sick sinus syndrome in children. Nonspecific fibrotic (scar-like) degeneration of the conduction system is often the cause. Coronary artery disease, hypertension (high blood pressure), and aortic and mitral valve diseases may be associated with sick sinus syndrome, although this association may only be incidental.