What are the causes of premature ventricular contractions (PVCs)?

Causes of Premature Ventricular Contractions (PVCs)

The primary causes of premature ventricular contractions (PVCs) include structural heart disease, electrolyte abnormalities, thyroid dysfunction, stimulant use, and high levels of physical or emotional stress. 1

Common Etiologies of PVCs

Cardiac Causes

• Structural heart disease:
  • Coronary artery disease
  • Cardiomyopathies (dilated, hypertrophic, arrhythmogenic)
  • Valvular heart disease
  • Myocarditis
  • Congenital heart defects

Metabolic and Systemic Causes

• Electrolyte abnormalities:
  • Hypokalemia
  • Hypomagnesemia
  • Hypocalcemia
• Thyroid dysfunction (particularly hyperthyroidism)
• Acid-base disturbances

External and Lifestyle Factors

• Stimulant use:
  • Caffeine
  • Alcohol
  • Tobacco
  • Recreational drugs (cocaine, amphetamines)
• Medications:
  • Sympathomimetics
  • Certain antiarrhythmics (proarrhythmic effect)
  • Digoxin toxicity
• High levels of physical or emotional stress 1, 2

Risk Factors for PVCs

• Advancing age (prevalence increases with age)
• Taller height
• Higher blood pressure
• History of heart disease
• Reduced physical activity
• Smoking 2

Clinical Significance Based on PVC Burden

The clinical significance of PVCs varies depending on their frequency (burden):

PVC Burden	Risk Level	Clinical Significance
<2,000/24h or <1%	Very Low	Generally benign
2,000-10%	Low to Intermediate	May require monitoring
10-15%	High	Minimum threshold that can result in cardiomyopathy
>15%	Very High	Strong association with adverse outcomes
≥24%	Extremely High	Independently associated with cardiomyopathy

1, 3

Pathophysiological Mechanisms

PVCs can arise through several mechanisms:

• Triggered activity (early or delayed afterdepolarizations)
• Enhanced automaticity (abnormal impulse generation)
• Reentry (abnormal conduction pathways) 2

Important Clinical Considerations

• While often considered benign, PVCs can be a marker for underlying cardiac disease and require appropriate evaluation 4, 5
• When PVCs exceed 10% of total heartbeats, patients may experience fatigue and exertional dyspnea 3
• PVC burden >20% is associated with development of cardiomyopathy and heart failure (PVC-induced cardiomyopathy) 3, 6
• Polymorphic PVCs warrant more thorough investigation as they may indicate more serious underlying pathology 5

Diagnostic Approach for Identifying Causes

• 12-lead ECG to assess PVC morphology and identify patterns suggesting specific origins
• 24-hour Holter monitoring to quantify PVC burden
• Echocardiography to evaluate for structural heart disease
• Cardiac magnetic resonance imaging when structural heart disease is suspected
• Laboratory testing for electrolyte abnormalities and thyroid function
• Exercise stress testing to assess relationship between PVCs and exertion 1, 2

Clinical Pitfalls to Avoid

• Dismissing frequent PVCs (>10%) as benign without adequate evaluation
• Failing to identify reversible causes (electrolyte abnormalities, medication effects, stimulant use)
• Not recognizing the potential for PVC-induced cardiomyopathy in patients with high PVC burden
• Overlooking polymorphic PVCs, which may indicate underlying myocardial ischemia or other serious pathology 1, 5