EKG

Sick Sinus Syndrome

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Sick Sinus Syndrome, Tachycardia-Bradycardia Syndrome, Bradycardia-Tachycardia Syndrome, Tachy-Brady Syndrome

  • Definition
  1. Disorder interfering with sinus node pacing function
  • Epidemiology
  1. Prevalence: 1 in 600 cardiac patients over age 65 years
  2. Mean age: 68 years old (median 74 years old)
  • Causes
  • Intrinsic
  1. Older age (over 65 years)
    1. Sinoatrial node age-related idiopathic degenerative fibrosis
    2. Sinoatrial node inherited ion channel dysfunction
      1. May be comorbid with sinoatrial node degenerative fibrosis
    3. Sinoatrial node remodeling
      1. Congestive Heart Failure
      2. Atrial Fibrillation
      3. 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. Children
    1. Follows Congenital Heart Disease surgical correction
    2. Congenital abnormalities or SA node artery deficiency
  • Causes
  • Extrinsic (may also mimic Sick Sinus Syndrome)
  1. Obstructive Sleep Apnea
  2. Vagal tone increased (e.g. athletes while sleeping)
  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 III)
    2. Beta Blockers
    3. Nonhydropyridine Calcium Channel Blockers
    4. Digoxin
    5. Lithium
    6. Sympatholytic medications
  • 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
  • Signs
  • Monitor rhythm while performing procedures
  1. Valsalva response absent or minimal (no pulse increase)
  2. Carotid massage induces Sinus Arrest >3 seconds
  • 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
  • Diagnostics
  • Monitoring
  1. Correlate symptom diary with ambulatory monitoring
    1. Holter Monitor (preferred)
      1. 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. Exercise Stress Test
      1. Chronotropic incompetence (inadequate Heart Rate response to Exercise)
      2. Common for Sick Sinus Syndrome patients to fail to reach a maximal Heart Rate over 120
    2. Electrophysiology (less commonly indicated)
  • Diagnostics
  • EKG Findings
  1. Atrial Bradyarrhythmia (inappropriately)
    1. Sinus Bradycardia
    2. Sinus Arrest (may present as junctional rhythm or junctional escape beats)
    3. Second Degree Heart Block (Mobitz Type I or II)
    4. Atrial Fibrillation with slow ventricular response
  2. Tachycardia (present in >50% of Sick Sinus Syndrome cases)
    1. Atrial Fibrillation
    2. Atrial Flutter
    3. Atrial Tachycardia (Narrow Complex Tachycardia)
  3. Alternating Tachycardia-Bradycardia
    1. Tachycardia-Bradycardia Syndrome
    2. Typically associated with Atrial Fibrillation or Atrial Flutter
  • 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
  • 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
  • Management
  1. 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 due to the longterm 50% risk for Atrioventricular Block in Sick Sinus Syndrome
  2. Tachyarrhythmia control (use only with Pacemaker)
    1. Beta Blocker
    2. Calcium Channel Blocker
    3. Digoxin
  3. Anticoagulation with Coumadin
    1. See Anticoagulation in Atrial Fibrillation
    2. Indications
      1. Atrial Fibrillation or Atrial Flutter
      2. Tachycardia-Bradycardia Syndrome
  • Prognosis
  1. Best prognosis with Sinus Bradycardia only (no Tachycardia or tachy-brady)
  • 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. Semelka (2013) Am Fam Physician 87(10): 691-6 [PubMed]