PVC Localization on ECG: A Quick Guide for Clinicians

PVC Localization on ECG: Lets start with this ECG Case:

Premature ventricular contractions (PVCs) are common arrhythmias often seen on routine ECGs or Holter monitors. While isolated PVCs are frequently benign, identifying their site of origin can be clinically important—especially in patients with symptoms, frequent ectopy, or underlying structural heart disease. ECG morphology offers valuable clues to help localize the origin of these ectopic beats within the ventricles.

Basic Principles:

PVCs originate from a single focus in the ventricular myocardium. Because of this, the activation spreads outside the normal conduction system, creating wide and bizarre QRS complexes. The QRS morphology and axis during a PVC provide hints about where in the ventricles the beat originates.

Key Clues to Localization:

1. Outflow Tract PVCs (RVOT/LVOT)

Most common type in structurally normal hearts.

LBBB pattern in V1 (dominant S wave).

Inferior axis (positive QRS in II, III, aVF) — indicating superior origin.

RVOT PVCs show early R-wave transition (V3 or later), whereas LVOT PVCs tend to transition earlier (V1–V2).

2. Fascicular PVCs (Left Ventricular Septum)

Seen in young patients; often idiopathic.

Relatively narrow QRS with RSR' or RBBB pattern.

Right axis deviation or superior axis in posterior fascicular origin.

3. Mitral/Tricuspid Annulus PVCs

Variable morphology, often with sharp notching and slightly wider QRS.

May mimic outflow tract PVCs but with different axis and transition patterns.

Often require detailed mapping for exact localization.

4. Epicardial Origin

Broader QRS, initial slurring (pseudo-delta wave), and delayed intrinsicoid deflection.

Precordial QRS transition is delayed (after V4).

Often found near coronary venous system or outflow tract region.

Clinical Pearls:

Always compare PVC morphology across multiple leads.

Look for axis, bundle branch pattern in V1, and precordial transition.

Outflow tract PVCs are most common—and usually benign.

Epicardial or multiple morphologies may suggest structural heart disease.

Understanding PVC localization can guide further testing (like cardiac MRI or electrophysiology study) and help determine suitability for catheter ablation.

Author’s Note:

ECG remains a powerful, low-cost tool. With practice, PVC localization can be quickly assessed at the bedside, giving deeper insights into patient management.