Sick sinus syndrome

A group of abnormal heart arrhythmias presumably caused by a malfunction of the sinus node, the heart’s primary pacemaker.

Bradycardia-tachycardia syndrome is a variant in which slow arrhythmias and fast arrhythmias alternate.

Relatively uncommon process.

Sick sinus syndrome (SSS), an important cause of pacemaker implantation.

In 20,572 participants free of prevalent atrial fibrillation and pacemaker therapy at baseline, 291 developed SSS over 17 years of follow-up (Atherosclerosis Risk In Communities) study and the CHS (Cardiovascular Health Study),

SSS is associated with several factors, including advanced age and white race.

The incidence is approximately 78,000 in 2012.

Abnormal heart rhythms include: sinus arrest, sinus node exit block, sinus bradycardia, and other types of bradycardia.

May be associated with tachycardias including such as paroxysmal supraventricular tachycardia (PSVT) and atrial fibrillation.

Tachycardias that occur with SSS are characterized by a long pause after the tachycardia.

May be caused and worsened by medications such as digitalis, calcium channel blockers, beta-blockers, sympatholytic medications, and anti-arrhythmics.

Caused by entities that cause damage to the conduction system and include sarcoidosis, amyloidosis, Chagas’ disease, and other cardiomyopathies.

More common in elderly adults with scar-like degeneration of the cardiac conduction system.

In children cardiac surgery, especially to the atria, is a common cause of SSS.

Associated with coronary artery disease, hypertension, and aortic and mitral valve diseases.

Patients may be asymptomatic, or may experience dizziness, chest pain, palpitations, dyspnea, fatigue and Stock-Adams attacks.

Holter monitoringmay be necessary to demonstrate arrhythmias that are transient.

ECG may show: sinus bradycardia, sinus arrest, sinoatrial block, trial fibrillation with slow ventricular response, prolonged asystolic period after tachycardias, atrial flutter, ectopic atrial tachycardia, sinus node reentrant tachycardia.

Electrophysiologic tests have low specificity and sensitivity for diagnosis.

Tilt table testing may help to diagnose the process.

Involves a dysfunction in the ability of the sinus node to generate or transmit an action potential to the atria.

Includes a variety of disorders grouped within this clinical syndrome and includes: signs and symptoms related to cerebral hypoperfusion in association with sinus bradycardia, sinus arrest, sinoatrial (SA) block, carotid hypersensitivity, or alternating episodes of bradycardia and tachycardia.

Most frequent in elderly patients with concomitant cardiovascular disease.

Has an unpredictable clinical course.

Most cases idiopathic.

Some cases have a functional decrease in the number of nodal cells, or have antinodal antibodies.

Has a poor prognosis, with 5-year survival rates in the range of 47-69%.

Pacemakers have been used in the treatment of sick sinus syndrome with bradyarrhythmias.

SSS associated tachyarrhythmias respond well to medical therapy.

In patients with bradyarrhythmias-tachyarrhythmias drugs utilized to control tachyarrhythmia may exacerbate bradyarrhythmia, so that implanting a pacemaker is performed before drug therapy is begun.

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