What are the presentations and management of sick sinus syndrome?

Sick Sinus Syndrome: Presentation and Management

Sick sinus syndrome (SSS) presents primarily with symptoms of cerebral hypoperfusion including syncope or near-fainting occurring in approximately 50% of patients, and is best managed with dual-chamber rate-adaptive pacemaker (DDDR) placement for symptomatic patients. 1

Clinical Presentation

Common Manifestations

• Electrocardiographic findings:

  • Sinus bradycardia
  • Sinus arrest
  • Sinoatrial block
  • Tachy-brady syndrome (alternating patterns of bradycardia and tachycardia) in at least 50% of patients 1

• Symptoms related to end-organ hypoperfusion:

  • Syncope (occurs in ~50% of patients)
  • Pre-syncope
  • Dizziness
  • Palpitations
  • Fatigue
  • Exercise intolerance 1, 2

Important Clinical Considerations

• Symptoms are often subtle early on and become more obvious as the disease progresses 1
• Many patients may be asymptomatic or have nonspecific symptoms, making diagnosis challenging 2
• SSS predominantly affects older adults 1
• Symptoms must correlate with bradyarrhythmia for diagnosis of symptomatic SSS 3

Diagnostic Approach

1. Initial ECG evaluation - May show:

   • Sinus bradycardia
   • Sinus pauses/arrest
   • Sinoatrial block
   • Alternating bradycardia and tachycardia 1, 2

2. Extended monitoring when initial ECG is non-diagnostic:

   • 24-hour Holter monitoring
   • Outpatient event monitoring
   • Implantable loop recorder
   • Inpatient telemetry monitoring 3

3. Electrophysiologic studies (EPS) in selected patients:

   • Consider when non-invasive evaluation is non-diagnostic
   • Assesses sinus node recovery time (SNRT) and sinoatrial conduction time (SACT) 3

4. Correlation of symptoms with arrhythmias is essential for diagnosis 3

Management

Pacemaker Therapy

• Primary treatment: Dual-chamber rate-adaptive pacing (DDDR) is preferred over single-chamber pacing 3
• Benefits of pacemaker therapy:
  • Decreases syncope episodes 4
  • Lowers incidence of heart failure 4
  • Reduces incidence of paroxysmal atrial fibrillation 3
  • Decreases need for reoperation 3
  • Improves quality of life 1, 2
  • Preserves optimal atrioventricular coupling 3

Medication Management

1. Review and discontinue bradycardia-inducing medications when appropriate 3

2. For tachycardia component of tachy-brady syndrome:

   • Beta-blockers as first-line for adrenergically mediated tachycardia 3
   • Non-dihydropyridine calcium channel blockers (use with caution in hypotension or heart failure) 3
   • For patients with heart disease: consider digitalis or amiodarone 3
   • For patients with minimal/no heart disease: consider flecainide, propafenone, or sotalol 3

3. For vagally-mediated sinus arrhythmia:

   • Anticholinergic agents like disopyramide may be considered 3

4. Theophylline:

   • May reduce heart failure incidence but less effective than pacemakers for preventing syncope 4
   • Not commonly used in current practice

Special Considerations

• Anticoagulation: Should be considered in patients with SSS and atrial fibrillation due to increased thromboembolic risk (15.2% risk in unpaced patients vs 1.3% in age-matched controls) 3

• Monitoring for atrial fibrillation: Patients with SSS have high incidence of developing AF (8.2% at diagnosis, increasing to 15.8% during follow-up) 3

• Atrial flutter: Associated with increased risk of incident SSS and its complications, especially in patients with coexisting atrial fibrillation 5

Follow-up Care

• Regular assessment of symptom control
• ECG monitoring to evaluate treatment efficacy
• Regular device checks for patients with pacemakers
• Continued monitoring for development of atrial fibrillation 3

Clinical Pitfalls to Avoid

• Misdiagnosis: Due to nonspecific symptoms and elusive findings on ECG or Holter monitor 2
• Inadequate monitoring: Symptoms may be intermittent, requiring extended monitoring periods
• Focusing only on bradycardia: Tachy-brady syndrome requires management of both components
• Overlooking extrinsic causes: Medication effects, metabolic disorders, or autonomic dysfunction may mimic or exacerbate SSS 1
• Single-chamber ventricular pacing: Associated with higher incidence of atrial fibrillation and thromboembolic events compared to dual-chamber pacing 2