23-19: Right Bundle Branch Block

ECG Findings

• Wide QRS complex > 120 ms.

• rsR’ pattern in leads V₁ and V₂.

• Slurred S wave in lateral leads (I, aVL, V₅-V₆).

• ST depression and T-wave inversion is typical in the right precordial leads (V₁-V₃).

• When all of these criteria are met except that the QRS duration is < 120 ms, an incomplete right bundle branch block (RBBB) pattern is diagnosed.

Pearls

1. In RBBB, conduction through the right bundle is delayed, whereas depolarization through the left bundle occurs at normal speed. This creates a secondary R wave (an rsR’ pattern), ST depression, and T-wave inversion in the right precordial leads (V₁-V₃), as well as a slurred S wave in the lateral leads.

2. Acute right heart strain, as may occur with pulmonary embolism, may result in the appearance of an incomplete or complete RBBB pattern.