If QRS is wide in V1, which lead should also be checked to confirm findings?

When the QRS complex is wide in lead V1, it is essential to check lead V6 to confirm the findings because lead V6 is positioned laterally in the precordial lead system, and a wide QRS in both V1 (which provides information about the right side of the heart) and V6 (which provides information about the left side) can help differentiate between certain types of conduction abnormalities.

A wide QRS complex can indicate various conditions, such as a bundle branch block or a ventricular rhythm. Observing the QRS duration and morphology in V6 can provide critical insights into whether the wide complex originates from a ventricular source or is related to a specific bundle branch conduction delay. If both V1 and V6 demonstrate a wide QRS, it could suggest a more extensive conduction problem, whereas a narrow QRS in V6 may indicate an isolated right-sided issue.

Comparatively, leads like II and III are primarily limb leads that reflect different angles of the heart's electrical activity and may not provide the same regional insights regarding right versus left ventricular conduction as the precordial leads do. Lead V5 follows a similar rationale as V6, but V6 tends to better confirm lateral wall versus right wall conduction issues when considering the