Patients with pre-existing Left Bundle Branch Block are a challenge when they present with chest pain. The Sgarbossa criteria are often cited, but are frequently used incorrectly. We look at the original Sgarbossa criteria as well as the Smith-modified Sgarbossa criteria and go over how they should be used. Chao-Wei Hwang, M.D., Ph.D. Johns Hopkins University School of Medicine Cardiac Cath Lab, Frederick Health Hospital