What are extrasystoles?

Extrasystoles: Definition, Types, and Clinical Significance

Extrasystoles are premature heartbeats that occur when cardiac cells are activated earlier than expected in the normal cardiac cycle, originating from sites outside the normal conduction pathway. These early beats can originate from either the atria (supraventricular extrasystoles) or ventricles (ventricular extrasystoles) and represent one of the most common cardiac rhythm disturbances encountered in clinical practice.

Types of Extrasystoles

1. Ventricular Extrasystoles (VEs)

• Also called premature ventricular contractions (PVCs)
• Originate from a site beyond the bifurcation of the bundle of His 1
• Characterized by:
  • Wide QRS complex (typically >120 ms)
  • Usually followed by a compensatory pause
  • May appear in patterns: isolated, bigeminy (every other beat), trigeminy (every third beat)
  • Can be monomorphic (same morphology) or polymorphic (different morphologies)

2. Supraventricular Extrasystoles (SVEs)

• Also called premature atrial contractions (PACs)
• Originate from the atria or AV junction
• Characterized by:
  • Premature P wave with abnormal morphology
  • Normal or near-normal QRS complex (unless aberrantly conducted)
  • Usually followed by an incomplete compensatory pause

3. His Bundle Extrasystoles

• Less common but clinically important
• Can manifest as premature atrial, junctional, or ventricular beats 2
• May mimic second-degree AV block patterns

Diagnostic Approach

1. ECG Findings:

   • Premature beats with abnormal morphology
   • For VEs: wide QRS complex, often with compensatory pause
   • For SVEs: premature P wave with abnormal morphology, usually normal QRS

2. 24-hour Holter Monitoring:

   • Quantifies extrasystole burden (percentage of total beats)
   • Identifies patterns (isolated, couplets, runs)
   • Helps determine if extrasystoles are exercise-induced or occur at rest

3. Exercise Testing:

   • Useful to determine if extrasystoles increase or decrease with exercise
   • Exercise-induced extrasystoles may suggest underlying ischemia
   • Exercise-suppressed extrasystoles often suggest benign origin

4. Echocardiography:

   • Essential to rule out structural heart disease
   • Particularly important in patients with frequent VEs (>10,000/day)

Clinical Significance

Ventricular Extrasystoles

• In Healthy Hearts:

  • Common finding (5% of normal population) 3
  • Usually benign when isolated and monomorphic
  • Asymptomatic individuals with VE burden <5% generally require no further investigation 4

• In Structural Heart Disease:

  • May indicate increased risk for sustained ventricular arrhythmias
  • Particularly concerning after myocardial infarction
  • Risk factors include: left ventricular dysfunction and complex/repetitive VEs 3

Supraventricular Extrasystoles

• Generally considered benign when isolated
• Frequent SVEs may be associated with increased risk of developing atrial fibrillation
• Early detection of frequent SVEs in patients with cardiovascular risk factors may help reduce risk of stroke and other complications 4

Management Approach

When to Treat

1. Symptomatic Patients:

   • Treatment primarily for symptom relief
   • Consider treatment when symptoms significantly affect quality of life

2. Patients with Structural Heart Disease:

   • More aggressive approach warranted
   • VEs >10 per hour in heart disease patients may require treatment 3
   • Repetitive or complex VEs in post-MI patients require urgent treatment

3. Asymptomatic Patients without Heart Disease:

   • Generally no treatment required
   • Monitor if VE burden is high (>10,000/24 hours) due to risk of tachycardia-induced cardiomyopathy

Treatment Options

1. Conservative Management:

   • Lifestyle modifications (reduce caffeine, alcohol, stress)
   • Correction of electrolyte abnormalities
   • Discontinuation of offending medications

2. Pharmacological Treatment:

   • Beta-blockers: first-line for symptomatic patients
   • Non-dihydropyridine calcium channel blockers: alternative for SVEs
   • Class III antiarrhythmics: for refractory cases with structural heart disease
   • Lidocaine: drug of choice for ventricular ectopy in acute myocardial infarction 5

3. Catheter Ablation:

   • First-line treatment for symptomatic, idiopathic ventricular extrasystoles from the RVOT and left bundle branch 4
   • Consider when extrasystoles are highly symptomatic despite medical therapy
   • Success rates >80% for focal sources

Special Considerations

1. Post-Myocardial Infarction:

   • VEs increase risk of sudden cardiac death
   • Lidocaine is the drug of choice for management of ventricular ectopy 5
   • Initial IV bolus of 1 mg/kg (max 100 mg) followed by maintenance infusion

2. Tachycardia-Induced Cardiomyopathy:

   • Can develop with very frequent extrasystoles (typically >15% of total beats)
   • Often reversible with successful treatment of extrasystoles

3. Diagnostic Pitfalls:

   • His bundle extrasystoles can mimic various arrhythmias and conduction disorders 2
   • Distinguishing benign from pathological extrasystoles requires comprehensive evaluation

Remember that while many extrasystoles are benign, their clinical significance depends heavily on the presence of underlying heart disease, symptoms, and extrasystole burden. Proper evaluation is essential for appropriate management decisions.