Why Is the QRS Negative Near the Origin of PVCs and Ventricular Tachycardia? ECG Polarity Explained

A ventricular ectopic beat spreads away from its site of origin through the myocardium. The ECG polarity depends on the direction of depolarization relative to a lead.

If the electrical wavefront moves toward a lead → the QRS is positive.

If it moves away from a lead → the QRS is negative.

In PVCs or VT, the earliest activation begins at the ectopic focus. Therefore, leads “looking at” the site of origin see activation moving away from them, producing a predominantly negative QRS complex (QS or rS pattern).

Example:

A PVC arising from the right ventricle spreads mainly toward the left ventricle.

Right precordial leads like V1 are near the origin and see activation moving away → negative QRS in V1.

Left-sided leads may see activation moving toward them → positive QRS.

This principle is used for VT localization:

Negative inferior leads → inferiorly directed activation → superior origin.

LBBB morphology VT usually originates in the right ventricle.

RBBB morphology VT usually originates in the left ventricle.

Think of it like throwing a stone into water: the ripple moves outward from the origin. Any observer sitting near the starting point sees the wave moving away from them.

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