What causes Premature Ventricular Contractions (PVCs)?

Causes of Premature Ventricular Contractions (PVCs)

Premature ventricular contractions (PVCs) are commonly caused by underlying cardiac disease, but can also occur in healthy individuals due to various physiological and environmental factors. 1

Common Causes of PVCs

Cardiac Structural Abnormalities

• Ischemic heart disease - Most life-threatening ventricular arrhythmias are associated with ischemic heart disease, particularly in older patients 1
• Cardiomyopathies - Including dilated, hypertrophic, and arrhythmogenic right ventricular cardiomyopathy
• Valvular heart disease - Particularly mitral valve prolapse 1
• Left ventricular dysfunction - PVCs can both result from and contribute to LV dysfunction 1
• Myocarditis - Inflammation of the heart muscle
• Congenital heart disease - Various structural abnormalities

Electrophysiological Disturbances

• Electrolyte abnormalities - Particularly potassium, magnesium, and calcium imbalances 1
• Acid-base disturbances - Can trigger electrical instability in the heart 1
• Prolonged QT interval - Can predispose to ventricular arrhythmias 1
• Purkinje fiber injury - Partially injured Purkinje fibers can trigger PVCs 1

Medications and Substances

• Stimulants - Caffeine, nicotine, alcohol, and illicit drugs
• Medications - Various drugs can trigger PVCs or worsen existing ones:
  • Certain antiarrhythmic drugs (paradoxically)
  • Digoxin toxicity (can cause bidirectional VT) 1
  • QT-prolonging medications (www.crediblemeds.org) 1
  • Medications that can induce Brugada pattern (www.brugadadrugs.org) 1

Physiological Factors

• Age - PVCs increase in frequency with age 1
• Height - Taller individuals have higher PVC frequency 2
• Hypertension - Higher blood pressure predicts greater PVC frequency 2
• Physical inactivity - Less physical activity is associated with more PVCs 2
• Smoking - Associated with increased PVC frequency 2
• Stress and anxiety - Heightened sympathetic tone
• Sleep apnea - Can manifest as nocturnal arrhythmias 1

Clinical Significance and Burden

PVCs are extremely common, occurring in approximately:

• 0.6% of those <20 years of age
• 2.7% of those >50 years of age on 12-lead ECGs
• About 50% of all people with or without heart disease on longer-term monitoring 1

The burden of PVCs can have significant implications:

• Very frequent PVCs (>10,000-20,000 per day) can be associated with depressed LV function 1
• PVC burden >24% can induce or contribute to cardiomyopathy 3
• Multifocal PVCs are associated with increased risk of death and cardiovascular adverse outcomes 1

Important Clinical Considerations

1. PVC-induced cardiomyopathy is an emerging entity where frequent PVCs can lead to reversible left ventricular dysfunction 4, 3, 5

2. PVC origin matters:

   • Right ventricular outflow tract (RVOT) PVCs typically have LBBB morphology with inferior axis and are generally considered benign 1
   • However, RVOT PVCs with QRS duration >160ms may suggest early arrhythmogenic right ventricular cardiomyopathy (ARVC) 1

3. Evaluation threshold:

   • Finding ≥2 PVCs on an ECG should prompt more extensive evaluation to exclude underlying structural heart disease 1
   • Patients with ≥2,000 PVCs per 24 hours have up to 30% likelihood of underlying structural heart disease 1

4. Treatment considerations:

   • Treatment of PVCs with antiarrhythmic medications has not been shown to reduce mortality 1
   • In post-MI patients, class I sodium channel blockers increase mortality despite PVC suppression 1
   • Catheter ablation can be highly effective for symptomatic or high-burden PVCs 4, 3

Clinical Pitfalls to Avoid

1. Don't assume all PVCs are benign - While often asymptomatic, they may indicate underlying heart disease or lead to cardiomyopathy if frequent

2. Don't overlook modifiable factors - Address electrolyte abnormalities, medication effects, and lifestyle factors before proceeding to invasive treatments

3. Don't underestimate PVC burden - Standard 12-lead ECGs may miss significant PVC burden; consider 24-hour Holter monitoring when clinically indicated

4. Don't use Class I antiarrhythmics in post-MI patients - These medications increase mortality despite PVC suppression 1

5. Don't miss PVC-induced cardiomyopathy - Consider this diagnosis in patients with unexplained cardiomyopathy and frequent PVCs, as it may be reversible with PVC suppression 4, 3, 5