Left Bundle Branch Block is abbreviated LBBB. Which option best describes this finding?

• A. Mitral Valve Prolapse
• B. Left Bundle Branch Block
• C. Myocardial Infarction
• D. Endocarditis

Answer: (B)

The key idea is that LBBB is a shorthand for a specific electrical problem in the heart: a block in the left bundle branch. This means the left ventricle doesn’t get activated promptly because the electrical impulse is delayed as it travels through the left bundle. On an ECG, this shows up as a widened QRS complex (typically over 120 ms) with distinctive patterns in the left-sided leads (broad, often notched R waves in lateral leads, and changes in the septal Q waves). The other options describe different heart conditions—a valve issue (mitral valve prolapse), tissue death from a heart attack (myocardial infarction), or infection of the heart valves or lining (endocarditis)—which are not what LBBB stands for. So the description that matches the abbreviation is Left Bundle Branch Block.