Causes of Premature Ventricular Contractions (PVCs)
Premature ventricular contractions (PVCs) occur due to multiple etiologies including electrolyte abnormalities, structural heart disease, increased sympathetic tone, and idiopathic causes, with a PVC burden ≥10% being the minimum threshold that can result in cardiomyopathy. 1
Primary Causes of PVCs
Electrolyte Abnormalities
- Potassium imbalances: Hyperkalemia (especially >6.5 mmol/L) can trigger ventricular arrhythmias including PVCs 2
- Magnesium deficiency: Hypomagnesemia (<1.3 mEq/L) is associated with more frequent ventricular arrhythmias including PVCs 2
- Randomized controlled trials have demonstrated that magnesium supplementation significantly reduces PVC frequency in patients with heart failure 2
Structural Heart Disease
- Cardiomyopathies (dilated, hypertrophic, restrictive)
- Scarring from previous myocardial infarction
- Valvular heart disease
- Congenital heart abnormalities
- Myocarditis 3
Lifestyle and Environmental Factors
- Caffeine consumption
- Alcohol intake
- Stimulant use
- Stress and anxiety (increased sympathetic tone) 1
- Smoking 4
- Lack of physical activity 4
Medications and Toxins
- Drug overdose (prescribed, industrial, or recreational drugs) 2
- Psychotropic medications in toxic doses 2
Idiopathic PVCs
- Occur in structurally normal hearts without identifiable triggers
- Often originate from specific anatomical locations (e.g., right ventricular outflow tract - 52% of cases) 2
PVC-Induced Cardiomyopathy
An important bidirectional relationship exists between PVCs and cardiomyopathy:
- PVCs can be a result of underlying cardiomyopathy
- PVCs can cause cardiomyopathy (PVC-induced cardiomyopathy)
Risk factors for developing PVC-induced cardiomyopathy:
- PVC burden ≥10% appears to be the minimum threshold that can result in cardiomyopathy 1
- PVC burden ≥24% is independently associated with cardiomyopathy 2, 1
- In a referral heart failure population, tachycardia-induced cardiomyopathy was found in 6.8% of patients 2
- Among patients with idiopathic, frequent PVCs (>10/hour), 22% had left ventricular dysfunction 2
Clues That PVCs Are Causing Cardiomyopathy Rather Than Resulting From It
- Improvement of ejection fraction with treatment of the PVCs
- Presence of PVCs in a structurally normal heart followed by subsequent left ventricular dysfunction
- Normalization of ejection fraction after radiofrequency ablation (occurs in 82% of patients with LV dysfunction within 6 months) 2
Pathophysiological Mechanisms of PVCs
Three primary mechanisms can trigger PVCs:
- Triggered activity: Abnormal afterdepolarizations that reach threshold potential
- Enhanced automaticity: Accelerated spontaneous depolarization of ventricular cells
- Reentry: Circular electrical activity around a conduction barrier 4
Risk Stratification
PVC burden correlates with risk:
- <2,000 PVCs/24h: Very low risk
- 10-15% burden: Intermediate risk
15% burden: High risk
24% burden: Very high risk for cardiomyopathy 1
Clinical Implications
Understanding the causes of PVCs is crucial for appropriate management. While PVCs in structurally normal hearts are generally benign, they can indicate increased risk of sudden death in patients with structural heart disease 3. Additionally, high PVC burden may induce cardiomyopathy or worsen existing cardiac dysfunction 3.
The relationship between PVCs and cardiovascular outcomes is complex, with increasing evidence suggesting that even in apparently healthy individuals, a higher PVC frequency may be a risk factor for heart failure and death 4.