Which ECG characteristic is associated with a Lateral Left Bundle Branch Block?

The characteristic associated with a Lateral Left Bundle Branch Block (LBBB) is indeed a widened QRS complex, and this is typically shaped like an "M" in leads I and V6.

In Lateral LBBB, the conduction through the left bundle branch is impaired, leading to a delay in the activation of the left ventricle. This results in a prolonged QRS duration, often exceeding 120 milliseconds. The "M" shape observed in the leads, particularly in I and V6, indicates the pattern of ventricular depolarization where the left ventricle is depolarizing later than the right due to the block. This delayed activation contributes to the characteristic morphology of the QRS complex seen on the ECG.

Recognizing the typical "M" shape in the lateral leads is crucial for diagnosing LBBB, as it reflects the underlying electrical conduction issue in the heart. Understanding this characteristic appearance helps clinicians differentiate it from other types of bundle branch blocks or dysrhythmias.