What is a common characteristic of left bundle branch block on an EKG?

What is a common characteristic of left bundle branch block on an EKG?

• A. Widened QRS complexes
• B. Shortened PR interval
• C. Deep Q waves in leads I and aVL
• D. Inverted T waves in precordial leads

Answer: (A)

A common characteristic of left bundle branch block (LBBB) on an EKG is the presence of widened QRS complexes. In LBBB, there is a delay or blockage in the conduction through the left bundle branch of the heart's electrical conduction system, resulting in a prolonged QRS duration typically greater than 120 milliseconds. This widening occurs because the left ventricle depolarizes later than the right ventricle, leading to a distinctive appearance on the EKG. The QRS complexes often show a characteristic "M" shape in leads like V5 and V6.

Understanding that widening of the QRS complex is the hallmark of LBBB is essential for interpreting EKGs accurately, as it informs clinicians about potential underlying cardiac conditions and guides their diagnostic and therapeutic decisions.