 The population will be patients age 18 or older who present to the ED with LBBB and suspected ACS. The investigators expect the mean age of the study population to be approximately 60 years old, with most patients between 40 and 90. They anticipate that these patients will on average have multiple medical comorbidities given that those with LBBB and ACS are reported to be a sicker, older population with more cardiac risk factors than the usual ACS patient without LBBB. Patients under age 18 will be excluded because they extremely rarely have ACS andor LBBB. The investigators anticipate 300 subjects. 