Sick Sinus Syndrome
Basics
Basics
Basics
Description
Description
- Collective term used to describe dysfunction in the sinus node's automaticity and impulse generation
- Mechanism:
- Caused by progressive degeneration of the intrinsic functions of the sinoatrial (SA) node
- Characterized by periods of unexplained sinus node dysfunction leading to bradydysrhythmias, often without appropriate atrial or junctional escape rhythms
- Syndrome includes:
- Chronic SA nodal dysfunction
- Frequently depressed pacemakers
- Atrioventricular nodal conduction disturbances
- Sluggish return of SA nodal activity after DC cardioversion
- Presents in all age groups (mean age >65 yr)
- Male/female ratio is 1:1
Etiology
Etiology
- Intrinsic causes:
- Most common cause: Idiopathic degenerative fibrosis of sinus node
- Coronary artery or SA nodal artery disease
- Cardiomyopathy
- Ion-channel mutations/familial SSS
- Leukemia and metastatic disease
- Infiltrative cardiac or collagen vascular disease, including amyloidosis
- Surgical trauma
- Inflammatory diseases:
- Rheumatic heart disease
- Chagas disease
- Pericarditis and myocarditis
- Extrinsic causes (not true SSS but similar presentation):
- Drugs:
- β-blockers, calcium-channel blockers, clonidine
- Digoxin, amiodarone
- Lithium, phenytoin
- Autonomically mediated syndromes (cholinesterase deficiency)
- Hyperkalemia/hypokalemia
- Hypothyroidism
- Hypothermia
- Hypoglycemia
- Sepsis/infection
Pediatric Considerations
Associated with congenital abnormalities and subsequent surgical repair, as well as with congenital SA nodal artery deficiency
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