What are the types of Premature Ventricular Contractions (PVCs)?

Types of Premature Ventricular Contractions (PVCs)

Premature ventricular contractions (PVCs) can be classified into several distinct types based on their morphology, origin, and pattern, with specific clinical implications for each type.

Classification by Morphology and Pattern

Based on QRS Morphology

• Monomorphic PVCs: PVCs with consistent QRS morphology from beat to beat, suggesting a single focus of origin
• Multifocal PVCs: PVCs with varying QRS morphologies, indicating multiple ventricular origins and associated with higher cardiovascular risk 1

Based on Frequency

• Isolated PVCs: Single premature beats occurring sporadically
• Frequent PVCs: Defined as >30 PVCs per hour or at least 1 PVC on a standard 12-lead ECG 1
• Very frequent PVCs: >10,000-20,000 PVCs per day, which may be associated with depressed left ventricular function 1

Based on Pattern

• Bigeminy: Pattern where every other beat is a PVC
• Trigeminy: Pattern where every third beat is a PVC
• Couplets: Two consecutive PVCs
• Nonsustained ventricular tachycardia (NSVT): Three or more consecutive PVCs that terminate spontaneously in less than 30 seconds 1

Classification by Anatomical Origin

• Right Ventricular Outflow Tract (RVOT) PVCs:

  • Most common site of idiopathic PVCs
  • Typically present with LBBB morphology and inferior axis on ECG
  • Generally considered benign but can cause symptoms and rarely may be an early sign of ARVC (arrhythmogenic right ventricular cardiomyopathy) when QRS exceeds 160 ms 1

• Left Ventricular Outflow Tract (LVOT) PVCs:

  • Second most common site of idiopathic PVCs
  • Include PVCs originating from the aortic root

• Fascicular PVCs:

  • Originate from the Purkinje system
  • Often have a relatively narrow QRS complex

• Papillary Muscle PVCs:

  • Originate from the papillary muscles of either ventricle
  • Can be challenging to ablate due to anatomical considerations

• Annular PVCs:

  • Originate from the tricuspid or mitral valve annulus

Clinical Significance

Risk Stratification

• Benign PVCs: Typically isolated, monomorphic PVCs in patients without structural heart disease
• Potentially harmful PVCs:
  • PVCs comprising >10% of total heartbeats may cause symptoms like fatigue and dyspnea
  • PVCs comprising >20% of heartbeats may lead to cardiomyopathy and heart failure 2
  • Multifocal PVCs are associated with increased risk of death and adverse cardiovascular outcomes 1

PVC-Induced Cardiomyopathy

PVCs can cause or worsen cardiomyopathy through several mechanisms:

• High PVC burden (typically >10,000-20,000/day)
• Ventricular dyssynchrony from abnormal activation patterns
• Abnormal calcium handling
• Suppression of PVCs can lead to improvement in left ventricular function in these cases 3

Management Considerations

The need for treatment depends on:

1. Presence of underlying structural heart disease
2. PVC frequency and burden
3. Symptom severity
4. Evidence of PVC-induced cardiomyopathy

For frequent, symptomatic PVCs or those associated with LV dysfunction, treatment options include:

• Catheter ablation - particularly effective for focal PVCs with discrete anatomical origins
• Antiarrhythmic medications - with careful consideration of potential side effects

Important Caveats

• Even seemingly benign PVCs should be evaluated in the context of the patient's overall cardiac health
• Multiple PVCs (≥2) on a standard ECG should prompt more extensive evaluation including Holter monitoring, echocardiography, and exercise stress testing 1
• PVCs that increase during exercise may indicate underlying structural heart disease and warrant further investigation
• Treatment of PVCs with class I antiarrhythmic medications in post-MI patients or those with reduced LVEF can increase mortality risk 1

Understanding the specific type of PVCs present helps guide appropriate diagnostic evaluation and treatment decisions to improve outcomes related to morbidity, mortality, and quality of life.