What is a protected LM?

• A. Pre-existing bypass to left coronary system
• B. New bypass graft to left coronary artery
• C. Normal left main coronary artery anatomy
• D. Occlusion of the right coronary artery

Answer: (A)

A protected left main means there is a patent bypass graft to the left coronary circulation that can supply blood if the left main becomes compromised during intervention. This pre-existing graft provides protection to the left coronary system (LAD and LCx) during PCI of the left main, reducing the risk of catastrophic myocardial ischemia.

That’s why the description fits a pre-existing bypass to the left coronary system. A newly created bypass would not be considered the standard definition of a protected left main, and normal left main anatomy or occlusion of the right coronary artery do not provide this protective mechanism.