Sick sinus syndrome


Sick sinus syndrome, is a group of abnormal heart rhythms 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.

Signs and symptoms

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:
It can result in many abnormal heart rhythms, including sinus arrest, sinus node exit block, sinus bradycardia, and other types of bradycardia.
Sick sinus syndrome may also be associated with tachycardias such as atrial tachycardia and atrial fibrillation. Tachycardias that occur with sick sinus syndrome are characterized by a long pause after the tachycardia. Sick sinus syndrome is also associated with azygos continuation of interrupted inferior vena cava.

Causes

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.

Diagnosis

Ambulatory monitoring of the electrocardiogram 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.

Treatment

s have been used in the treatment of sick sinus syndrome.
Bradyarrhythmias are well controlled with pacemakers, while tachyarrhythmias 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.

Epidemiology

Sick sinus syndrome is a relatively uncommon syndrome in the young and middle-aged population. 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.