Pattern: Wide QRS with an rsR' in V1 and broad S waves in I and V6.

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Pattern: Wide QRS with an rsR' in V1 and broad S waves in I and V6.

Recognizing a right bundle branch block on ECG. The pattern described—a wide QRS complex, an rsR' pattern in V1, and broad S waves in leads I and V6—is classic for RBBB. The wide QRS (greater than 120 ms) shows that ventricular activation is prolonged because the impulse is not reaching the right ventriclethrough the normal pathway. In right bundle branch block, the left ventricle activates first via the normal left bundle, and the right ventricle is activated later, producing the rsR' configuration in V1 (often seen as the “bunny ears” with a second R wave). The broad, slurred S waves in the lateral leads I and V6 reflect the delayed activation of the right ventricle affecting those views. Left bundle branch block would present with a different pattern in the lateral leads—typically broad, notched R waves in I, aVL, V5–V6—and V1 often shows a wide, predominantly negative QRS or QS pattern rather than rsR'. Atrial flutter shows sawtooth flutter waves, not the described QRS morphology, and normal sinus rhythm would have a narrow QRS without rsR'.

Recognizing a right bundle branch block on ECG. The pattern described—a wide QRS complex, an rsR' pattern in V1, and broad S waves in leads I and V6—is classic for RBBB. The wide QRS (greater than 120 ms) shows that ventricular activation is prolonged because the impulse is not reaching the right ventriclethrough the normal pathway. In right bundle branch block, the left ventricle activates first via the normal left bundle, and the right ventricle is activated later, producing the rsR' configuration in V1 (often seen as the “bunny ears” with a second R wave). The broad, slurred S waves in the lateral leads I and V6 reflect the delayed activation of the right ventricle affecting those views.

Left bundle branch block would present with a different pattern in the lateral leads—typically broad, notched R waves in I, aVL, V5–V6—and V1 often shows a wide, predominantly negative QRS or QS pattern rather than rsR'. Atrial flutter shows sawtooth flutter waves, not the described QRS morphology, and normal sinus rhythm would have a narrow QRS without rsR'.

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