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This article is for Medical Professionals

Professional Reference articles are designed for health professionals to use. They are written by UK doctors and based on research evidence, UK and European Guidelines. You may find the Bradycardia (Causes, Symptoms, and Treatment) article more useful, or one of our other health articles.

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Synonyms: sinus node dysfunction, sinoatrial disease, tachy-brady syndrome

Sick sinus syndrome is a collection of conditions in which the ECG indicates sinus node dysfunction. It is characterised by sinus node dysfunction with an atrial rate inappropriate for normal requirements. Sick sinus syndrome is usually caused by idiopathic fibrosis of the sinus node.

Causes include:

Sleep apnoea may be a contributing factor by causing reduced cardiac oxygenation.[3] Paediatric causes include congenital abnormalities and sinoatrial nodal artery deficiency.

Sick sinus syndrome is most common in the elderly, but can occur in all ages. The average age of a person with sick sinus syndrome is 68 years and it develops in 1 in 600 patients with cardiac disease aged over 65 years.

  • Abnormalities in sick sinus syndrome include episodes of sinus bradycardia, sinus arrest or exit block, combinations of sinoatrial and atrioventricular nodal conduction disturbances, and atrial tachyarrhythmias.
  • At least 50% of people with sick sinus syndrome develop alternating bradycardia and tachycardia, also known as tachy-brady syndrome.[6]
  • Patients are often asymptomatic, or have subtle or nonspecific symptoms, such as fatigue.
  • Presentation may be with fatigue, dizziness, palpitations, and syncope or presyncope.
  • Central nervous system: dementia, irritability, lethargy, light-headedness, confusion, memory loss, nocturnal wakefulness, syncope.
  • Cardiovascular system: angina, arterial thromboemboli, cerebrovascular accident, congestive heart failure (dyspnoea), palpitations.
  • Other: digestive disturbances, dizziness, errors in judgment, facial flushing, fatigue, oliguria.
  • Symptoms associated with sick sinus syndrome may be aggravated by digoxin, verapamil, beta-blockers, sympatholytic agents such as clonidine and methyldopa, and anti-arrhythmic agents.[6]
  • Blood tests include renal function, electrolytes, TFTs and drug levels (eg, digoxin).
  • ECG: arrhythmias associated with sick sinus syndrome include:
    • Atrial bradyarrhythmias: sinus bradycardia, sinus arrest (with or without junctional escape), sinoatrial exit block (Mobitz type I or Mobitz type II block), ectopic atrial bradycardia, atrial fibrillation with slow ventricular response greater than three-second pause following carotid massage, long pause following cardioversion of atrial tachyarrhythmias.
    • Atrial tachyarrhythmias: atrial fibrillation, atrial flutter, atrial tachycardia, paroxysmal supraventricular tachycardia.
    • Ventricular (escape) tachyarrhythmia.
    • Alternating bradycardias and tachycardias: tachy-brady syndrome.
  • Ambulatory ECG to associate arrhythmias with symptoms.
  • Echocardiogram: associated structural and functional heart abnormalities.
  • The treatment of choice for symptomatic bradyarrhythmias in patients with sick sinus syndrome is the placement of a pacemaker.[8]
  • Dual-chamber pacemakers provide effective relief of symptoms and lower the incidence of atrial fibrillation, thromboembolic events, heart failure and mortality, when compared with ventricular pacemakers.
  • Beta-blockers, quinidine and digoxin may be used in conjunction with a pacemaker for tachyarrhythmias.
  • Anticoagulation will be needed for patients with atrial fibrillation.[9]

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Further reading and references

  1. Sick Sinus Syndrome 1, Autosomal Recessive, SSS1; Online Mendelian Inheritance in Man (OMIM)

  2. Thorolfsdottir RB, Sveinbjornsson G, Aegisdottir HM, et al; Genetic insight into sick sinus syndrome. Eur Heart J. 2021 May 2142(20):1959-1971. doi: 10.1093/eurheartj/ehaa1108.

  3. Gill J, Wu C; In-hospital Outcomes and Arrhythmia Burden in Patients with Obstructive Sleep Apnea and Heart Failure with Preserved Ejection Fraction. J Innov Card Rhythm Manag. 2022 Jun 1513(6):5033-5040. doi: 10.19102/icrm.2022.130602. eCollection 2022 Jun.

  4. Dakkak W, Doukky R; Sick Sinus Syndrome.

  5. Jabbour F, Kanmanthareddy A; Sinus Node Dysfunction.

  6. Hawks MK, Paul MLB, Malu OO; Sinus Node Dysfunction. Am Fam Physician. 2021 Aug 1104(2):179-185.

  7. Glikson M, Nielsen JC, Kronborg MB, et al; 2021 ESC Guidelines on cardiac pacing and cardiac resynchronization therapy. Europace. 2022 Jan 424(1):71-164. doi: 10.1093/europace/euab232.

  8. Dual-chamber pacemakers for the treatment of symptomatic bradycardia due to sick sinus syndrome and/or atrioventricular block; NICE Technology appraisal guidance, February 2005 - last updated November 2014

  9. Anticoagulation - oral; NICE CKS, June 2022 (UK access only)

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