In a right bundle branch block, where would the R, R' be found?

In a right bundle branch block, where would the R, R' be found?

• A. Leads A and B
• B. Leads III and aVF
• C. Leads V1 and V2
• D. Leads V5 and V6

Answer: (C)

In a right bundle branch block (RBBB), the characteristic feature is the presence of a typical "bunny-ear" pattern in the QRS complex seen in specific leads. This pattern is predominantly observed in leads V1 and V2.

In these leads, the R wave is usually followed by a second R wave (R'), which contributes to the visual appearance of the double peaks. This occurs because the right ventricle is depolarized later than the left due to the blockage of conduction through the right bundle branch, leading to a prolonged QRS complex and the distinctive morphology.

Leads V1 and V2 are specifically positioned such that they can directly capture the electrical activity of the right ventricle, making them the most reliable for identifying this unusual pattern associated with RBBB. RBBB typically causes a widening of the QRS complex (greater than 120 ms) and the bifid R wave appearance, confirming the diagnosis in these leads.

Therefore, detecting the R and R' waves in leads V1 and V2 is crucial for diagnosing right bundle branch block.