Cardiovascular Medicine Book

Information Resources


Sick Sinus Syndrome

Aka: Sick Sinus Syndrome, Tachycardia-Bradycardia Syndrome, Bradycardia-Tachycardia Syndrome, Tachy-Brady Syndrome, Sinus Node Dysfunction
  1. Definitions
    1. Sinus Node Dysfunction (Sick Sinus Syndrome, Tachy-Brady Syndrome)
      1. Disorder interfering with sinus node pacing function
  2. Epidemiology
    1. Incidence: 0.8 per 1000 person years
    2. Prevalence: 1 in 600 cardiac patients over age 65 years
    3. Peaks at ages 70 to 89 years old
      1. Mean age: 68 years old (median 74 years old)
  3. Causes: Intrinsic
    1. Older age (over 65 years)
      1. Sinoatrial Node age-related idiopathic degenerative fibrosis (most common cause)
        1. Peri-myocardial accumulation of elastic fiber, fatty tissue, fibrous tissue (increases with age)
      2. Sinoatrial Node inherited ion channel dysfunction (e.g. Brugada Syndrome)
        1. May be comorbid with Sinoatrial Node degenerative fibrosis
      3. Sinoatrial Node remodeling (delayed cardiac tissue voltage transmission)
        1. Congestive Heart Failure
        2. Atrial Fibrillation
        3. Muscular Dystrophy
        4. Cardiomyopathy
          1. Myocarditis (e.g. Diphtheria, typhoid)
          2. Rheumatic Fever
          3. Chagas Disease
        5. Infiltration
          1. Connective Tissue Disease
          2. Hemochromatosis
          3. Sarcoidosis
          4. Amyloidosis
      4. Sinus node artery atherosclerosis (from proximal right Coronary Artery)
        1. Less common contributing factor (<33%)
        2. Embolization of the Sinoatrial Node artery
        3. Transient Sinus Node Dysfunction may occur with Myocardial Infarction (increased vagal tone)
    2. Children and young adults
      1. Follows Congenital Heart Disease surgical correction
        1. Atrial Septal Defect
        2. Transposition of the Great Vessels
      2. SA Node artery deficiency
      3. Genetic ion channel disorders
        1. Brugada Syndrome
        2. HCN4
        3. SCN5A
  4. Causes: Extrinsic (may also mimic Sick Sinus Syndrome)
    1. Obstructive Sleep Apnea
    2. Vagal tone increased
      1. Athletes
      2. Sleep state
      3. Postmyocardial Infarction
    3. Autonomic Dysfunction
      1. Carotid Sinus Hypersensitivity
      2. Neurocardiogenic Syncope
      3. Vasovagal Syncope
    4. Metabolic disorder
      1. Hyperkalemia
      2. Hypokalemia
      3. Hypocalcemia
      4. Hypothermia
      5. Hypothyroidism
      6. Hypoxia
    5. Medications and toxins
      1. Antiarrhythmics (Class I and Class II)
      2. Amiodarone
      3. Amitriptyline
      4. Beta Blockers
      5. Cimetidine
      6. Nonhydropyridine Calcium Channel Blockers
      7. Digoxin
      8. Lithium
      9. Marijuana
      10. Nicotine
      11. Sympatholytic medications (Anesthesia)
    6. Structural or Physiologic Disorder Risk Factors
      1. Diabetes Mellitus (Diabetic atrial Myopathy)
      2. Hypertension
  5. Associated Conditions
    1. Atrial Fibrillation
    2. Atrioventricular Node Block
  6. Symptoms (associated with sinus pause or Bradycardia)
    1. Near Syncope or Syncope (50% of cases)
    2. Palpitations
    3. Angina Pectoris
    4. Fatigue
    5. Confusion or Altered Level of Consciousness
    6. Exercise intolerance
    7. Transient light headedness (may be described as Dizziness)
    8. Vague gastrointestinal symptoms
  7. Signs: Monitor rhythm while performing procedures
    1. Valsalva response absent or minimal (no pulse increase)
    2. Carotid massage induces Sinus Arrest >3 seconds
  8. Diagnosis
    1. Sick Sinus Syndrome requires correlation of Bradycardia and sinus pauses with symptoms
    2. Asymptomatic Bradycardia alone is insufficient to make the diagnosis of Sick Sinus Syndrome
      1. Consider other causes of Sinus Bradycardia
      2. Consider Obstructive Sleep Apnea
  9. Diagnostics: Monitoring
    1. Correlate symptom diary with ambulatory monitoring
      1. External Patch Recorder (e.g. Zio monitor) or Holter Monitor
        1. Continuous monitoring (Preferred) for 7-14 days
        2. Consider repeating if non-diagnostic initially
      2. Event Monitor
        1. Consider for non-diagnostic Holter Monitor or less frequent symptoms
    2. Other EKG testing to consider
      1. Electrophysiology (less commonly indicated)
      2. Exercise Stress Test (if Exercise related)
        1. Chronotropic incompetence
          1. Inadequate Heart Rate response to Exercise (maximum Heart Rate <80% of predicted)
          2. Common for Sick Sinus Syndrome patients to fail to reach a maximal Heart Rate over 120 bpm
    3. Transthoracic Echocardiogram Indications (structural heart disease suspected)
      1. Congestive Heart Failure
      2. Left Bundle Branch Block
      3. Mobitz II AV Block
      4. Third Degree Atrioventricular Block
  10. Diagnostics: EKG Findings
    1. Atrial Bradyarrhythmia (inappropriately)
      1. Sinus Bradycardia (<50 bpm)
      2. Sinus pauses > 3 sec
      3. Sinus Arrest
        1. May present as Junctional Rhythm or junctional escape beats
      4. Sinoatrial Exit Block
        1. May be associated with Tachycardia-Bradycardia Syndrome and Supraventricular Tachycardia
      5. Second Degree Heart Block (Mobitz Type I or II)
      6. Atrial Fibrillation with slow ventricular response
    2. Tachycardia
      1. Atrial Fibrillation
      2. Atrial Flutter
      3. Atrial Tachycardia (Narrow Complex Tachycardia)
    3. Tachycardia-Bradycardia Syndrome (present in >50% of Sick Sinus Syndrome cases)
      1. Alternating Tachycardia-Bradycardia
      2. Typically associated with Atrial Fibrillation or Atrial Flutter and higher risk of Cerebrovascular Accident
  11. Differential Diagnosis
    1. Physiologic responses (consider in asymptomatic Bradycardia)
      1. See Sinus Bradycardia
      2. Increased vagal tone during sleep (especially athletes)
      3. Obstructive Sleep Apnea
    2. Metabolic disorder
      1. Hypothyroidism
      2. Hypothermia
      3. Hypoxia
      4. Hyperkalemia
    3. Miscellaneous disorders
      1. Cardiomyopathy
      2. Collagen vascular disease
      3. Metastatic cancer
    4. Medications
      1. Digoxin
      2. Quinidine
      3. Amiodarone
      4. Beta Blockers
      5. Diltiazem
      6. Verapamil
      7. Clonidine
  12. Labs
    1. Basic metabolic panel (chem8)
    2. Hemoglobin A1C
    3. Thyroid Stimulating Hormone (TSH)
  13. Complications
    1. Cerebrovascular Accident (due to Thromboembolism)
      1. Associated with Tachy-Brady Syndrome and typically Atrial Fibrillation or Atrial Flutter
      2. Consider Anticoagulation (see below)
    2. Atrioventricular Block
      1. Prevalence: 0.5 to 1.5% of patients annually, ultimately affecting 50% of Sick Sinus Syndrome patients
    3. Myocardial Infarction
    4. Congestive Heart Failure
  14. Management
    1. See Symptomatic Bradycardia
    2. Hospitalization Indications
      1. Hemodynamic instability
        1. Hypotension (e.g. systolic Blood Pressure <90 mmHg)
        2. Ventricular Arrhythmia
      2. Severe symptoms
        1. Recurrent Syncope
        2. Angina
    3. Comorbidity management (see extrinsic factors above)
      1. Obstructive Sleep Apnea (i.e. CPAP)
      2. Hypothyroidism (i.e. Levothyroxine)
      3. Correction of Electrolyte abnormalities (e.g. Hypokalemia)
    4. Permanent implantable demand ventricular Pacemaker
      1. See Pacemaker for indications
      2. Sick Sinus Syndrome accounts for >50% pacers placed
      3. Dual chamber pacing is preferred
        1. Longterm 50% risk for Atrioventricular Block in Sick Sinus Syndrome
        2. However right atrial pacing is preferred over right ventricular pacing
          1. Right ventricular pacing is associated with decreased Cardiac Function and Arrhythmias
      4. Alternatives for those refusing Pacemaker placement
        1. Oral Phosphodiesterase Inhibitors (e.g. cilostazol, Theophylline) are positive chronotropes
    5. Tachyarrhythmia control (use only with Pacemaker)
      1. Beta Blocker
      2. Calcium Channel Blocker
      3. Digoxin
    6. Anticoagulation with Coumadin
      1. See Anticoagulation in Atrial Fibrillation
      2. Indications
        1. Atrial Fibrillation or Atrial Flutter
        2. Tachycardia-Bradycardia Syndrome
  15. Prognosis
    1. Best prognosis with Sinus Bradycardia only (no Tachycardia or tachy-brady)
  16. References
    1. Faddis in Ahya (2001) Washington Manual, p. 153
    2. Behrman (2000) Nelson Pediatrics, p. 1422-3
    3. Wagner (2001) Marriott's Electrocardiography, p. 402
    4. Adan (2003) Am Fam Physician 67(8):1725-38 [PubMed]
    5. Keller (2006) Am J Crit Care 15(2):226-9 [PubMed]
    6. Kusumoto (2019) J Am Coll Cardiol 74(7): e51-6 +PMID:30412709 [PubMed]
    7. Hawks (2021) Am Fam Physician 104(2):179-85 [PubMed]
    8. Semelka (2013) Am Fam Physician 87(10): 691-6 [PubMed]

Sick Sinus Syndrome (C0037052)

Definition (NCI) A constellation of signs and symptoms which may include syncope, fatigue, dizziness, and alternating periods of bradycardia and atrial tachycardia, which is caused by sinoatrial node dysfunction.
Definition (NCI_CTCAE) A disorder characterized by a dysrhythmia with alternating periods of bradycardia and atrial tachycardia accompanied by syncope, fatigue and dizziness.
Definition (MSH) A condition caused by dysfunctions related to the SINOATRIAL NODE including impulse generation (CARDIAC SINUS ARREST) and impulse conduction (SINOATRIAL EXIT BLOCK). It is characterized by persistent BRADYCARDIA, chronic ATRIAL FIBRILLATION, and failure to resume sinus rhythm following CARDIOVERSION. This syndrome can be congenital or acquired, particularly after surgical correction for heart defects.
Concepts Disease or Syndrome (T047)
MSH D012804
ICD10 I49.5
SnomedCT 266307005, 155373001, 36083008
English Syndrome, Sick Sinus, SICK SINUS SYNDROME, Sick Sinus Syndrome, sick sinus syndrome, sick sinus syndrome (diagnosis), Sick Sinus Node Syndrome, Syndrome sick sinus, SSS, Sick Sinus Syndrome [Disease/Finding], sick syndrome sinus, sinus sick syndrome, Sick sinus syndrome, Sick sinus syndrome (disorder), sick sinus; syndrome, syndrome; sick sinus, Syndrome, sick sinus
Italian Sindrome del seno malato, Malattia del nodo del seno, Sick sinus syndrome, Sindrome bradicardia-tachicardica, Sindrome del nodo del seno
Spanish Síndrome del seno enfermo, Síndrome del Seno Enfermo, SINDROME DEL NODO SINUSAL ENFERMO, Síndrome del Nodo Sino-Atrial, Síndrome Bradicardia-Taquicardia, Síndrome del Nodo Sinusal, Síndrome del Nodo Sinoatrial, síndrome de disfunción sinusal (trastorno), síndrome de disfunción sinusal, síndrome del seno enfermo, Síndrome del nodo sinusal enfermo
Swedish Sjuka sinus-syndrom
Japanese ドウフゼンショウコウグン, 静脈洞機能不全症候群, 洞不全症候群, 徐脈-頻脈症候群, 徐脈頻脈症候群, 洞機能不全症候群, 病的洞結節症候群
Czech sick sinus syndrom, Syndrom chorého sinu, Sick sinus syndrom, syndrom chorého sinu, syndrom nemocného sinusového uzlu
Portuguese Síndrome do Nó Sinusal, DOENCA DO NO SINUSAL, Síndrome do Nó Sinoatrial, Síndrome do Seio Enfermo, Síndrome do Seio Doente, Síndrome Bradicardia-Taquicardia, Síndrome do nódulo sinusal
Finnish Sairas sinus -oireyhtymä
French Maladie rythmique auriculaire, Maladie du noeud sinusal, Maladie de l'oreillette, Syndrome de brady-tachycardie, MRA (Maladie Rythmique Auriculaire), MALADIE DU SINUS, Maladie du sinus, Syndrome de bradycardie-tachycardie, Syndrome de dysfonctionnement sinusal
German SICK SINUS SYNDROM, Sick-Sinus Syndrom, Sick-Sinus-Syndrom, Sinusknoten-Syndrom, Syndrom des kranken Sinusknotens
Korean 굴기능부전 증후군
Polish Zespół chorej zatoki, Choroba węzła zatokowo-przedsionkowego, Niewydolność węzła zatokowego, Zespół chorego węzła zatokowego
Hungarian Sick-sinus-syndroma, Sinus csomó syndroma
Norwegian Syk sinus-syndrom, Sick sinus syndrome
Dutch sick sinus; syndroom, syndroom; sick sinus, sick-sinus syndrome, Sick sinus syndrome, Syndrome, sick sinus
Derived from the NIH UMLS (Unified Medical Language System)

Bradycardia-tachycardia syndrome (C0221047)

Concepts Disease or Syndrome (T047)
ICD10 I49.5
SnomedCT 74615001
Dutch bradycardie-tachycardiesyndroom, syndroom; tachycardie-bradycardie, tachycardie-bradycardie; syndroom
French Syndrome de bradycardie-tachycardie
German Bradykardie-Tachykardie-Syndrom
Italian Sindrome bradi-tachicardica
Portuguese Síndrome de bradicardia-taquicardia
Spanish Síndrome de bradicardia-taquicardia, taquicardia - bradicardia (trastorno), taquicardia - bradicardia
English Bradycardia-tachycardia syndrome, Bradycardia-tachycardia synd, Tachycardia-bradycardia syndrome, tachycardia bradycardia, bradycardia tachycardia syndrome, tachy-brady syndrome, brady-tachy syndrome, bradycardia-tachycardia syndrome, Tachycardia bradycardia syndrome, Tachycardia-bradycardia (diagnosis), bradyarrhythmia tachycardia-bradycardia, Tachycardia-bradycardia, Brady-tachy syndrome, Tachycardia-bradycardia (disorder), syndrome; tachycardia-bradycardia, tachycardia-bradycardia syndrome, tachycardia-bradycardia; syndrome, Syndrome, tachycardia-bradycardia
Japanese 徐脈頻脈症候群, ジョミャクヒンミャクショウコウグン
Czech Bradykardicko-tachykardický syndrom
Hungarian Bradycardia-tachycardia syndroma
Derived from the NIH UMLS (Unified Medical Language System)

Sinus Node Dysfunction (disorder) (C0428908)

Definition (NCI) A derangement in the normal functioning of the sinoatrial node. Typically, SA node dysfunction is manifest as sinoatrial exit block or sinus arrest, but may present as an absolute or relative bradycardia in the presence of a stressor. It may be associated with bradycardia-tachycardia syndrome
Concepts Disease or Syndrome (T047)
MSH D012804
ICD9 427.81
ICD10 I49.8
SnomedCT 60423000, 195100002
English Sinoatrial node dysfunction, Sinoatrial node dysfunct. NOS, Sinoatrial node dysfunction NOS, sinoatrial node dysfunction, sinoatrial node dysfunction (diagnosis), Sinus Node Diseases, Dysfunction, Sinus Node, Sinus Node Disease, Dysfunctions, Sinus Node, Sinus Node Dysfunction, Sinus Node Dysfunction (disorder), Sinoatrial node dysfunct, sinus node dysfunction, Sinoatrial node dysfunction NOS (disorder), Coronary sinus rhythm disorder, Sinus node dysfunction, Sinus node dysfunction (disorder), Rhythm disorder, coronary sinus
Dutch sino-atriale knoopdisfunctie
French Dysfonction du noeud sinusal
German Dysfunktion des sinuatrialen Knotens, Sinusknoten-Dysfunktion, Sinusknotenerkrankung, Sinusknotendysfunktion
Italian Disfunzione del nodo senoatriale, Disfunzione del nodo del seno
Portuguese Disfunção do nódulo sinoauricular, Disfunção do Nó Sinoatrial
Spanish Disfunción del nodo sinoauricular, Disfunción del Nodo Sino-Atrial, disfunción del nodo sinusal, SAI (trastorno), disfunción del nodo sinusal, SAI, disfunción del nódulo sinoauricular (trastorno), disfunción del nódulo sinoauricular, trastorno del ritmo del nódulo sinusal
Japanese 洞房節機能不全, ドウボウセツキノウフゼン
Czech Dysfunkce sinoatriálního uzlu, dysfunkce sinusového uzlu
Hungarian Sinoatrialis csomó működési zavara
Norwegian Sinusknutesykdom, Sykdom i sinusknute, Sykdom i sinusknuten, Sinusknutedysfunksjon
Derived from the NIH UMLS (Unified Medical Language System)

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