We aimed to identify the frequency of STEMI-equivalent in patients with suspected ACS and LBBB and determine the diagnostic value of electrocardiographic and echocardiographic features and propose the new algorithm. From the 793 patients performed emergent coronary angiography between 2012 and July 31, 2015, we examined data on 21 patients with LBBB. These patients classified into 3 groups according to the final diagnosis: (1) STEMI-equivalent, (6 patients, 28.6%), (2) non-ST-segment elevation myocardial infarction (NSTEMI) (6 patients, 28.6%), and (3) diagnoses other than myocardial infarction (non-MI) (9 patients, 42.8%). 6 patients with the ST-segment concordance criteria (score ≥3) were STEMI-equivalent. 7 patients with discordant ST-elevation of ≥5 mm (score=2) were NSTEMI or non-MI. Therefore ST-segment concordance was highly sensitive and specific for the diagnosis of STEMi-equivalent. Compared with NSTEMI patients, 9 non-Mi patients with normal angiogram had low EF (35.6±19.0 vs 56.0±13.0, p=0.04) and increased LV end-diastolic dimension (63.9±8.8 vs 51.7±6.4, p=0.012). Low EF and increased diastolic dimension of LV indicates normal coronary angiogram in patients without ST-segment concordance of Sgarbossa criteria. we propose the newly modified diagnostic algorithm in this population.