Sick sinus syndrome

Sick sinus syndrome
Classification and external resources
Specialty	cardiology
ICD-10	I49.5
ICD-9-CM	427.81
DiseasesDB	12066
MedlinePlus	000161
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Sick sinus syndrome (SSS), also called sinus dysfunction, or sinoatrial node disease ("SND"), is a group of abnormal heart rhythms (arrhythmias) presumably caused by a malfunction of the sinus node, the heart's primary pacemaker.Tachycardia-bradycardia syndrome is a variant of sick sinus syndrome in which the arrhythmia alternates between slow and fast heart rates. Tachycardia-bradycardia syndrome is often associated with ischemic heart disease and heart valve disease.

Even though many types of sick sinus syndrome produce no symptoms, a person may present with one or more of the following signs and symptoms:

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

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. The mechanism is related to delayed escape. Congenital SSS can be due to mutations of the gene responsible for formation of Alpha subunit of sodium channel (SCN5A).

Ambulatory monitoring of the electrocardiogram (ECG) may be necessary because arrhythmias are transient. The ECG may show any of the following:

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.

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