To investigate the clinical manifestations of a pulmonary embolism (PE) in patients visiting the Emergency Department (ED) and to identify possible prognostic factors among the patients. Patients who suspected as PE and presented to the ED with chest tightness, chest pain, or syncope were enrolled. Wells score, revised Geneva score, and PE severity Index (PESI) were all recorded for analysis. Twelve patients who were diagnosed with a PE after a serial work-up were further analyzed for possible prognostic factors. The demographic characteristics, serum lab data, clinical presentations, management strategies, computed tomography (CT) angiography findings, and final outcomes were analyzed retrospectively. Chi-squared tests with Fisher's exact tests, and t-test analyses were applied to evaluate the prognostic factors. Among the 763 patients enrolled, poor prediction effectiveness of Geneva score and Wells score were noticed, and PESI was also found with no significant predictive value in our study group. The initial vital signs, syncope, chest pain, leg edematous changes, dyspnea, D-dimer levels, CT angiography-measured thrombus diameter, the presence of a right atrium (RA) or right ventricular (RV) thrombus, and presence of lung consolidations all revealed no predictive values in this study (p > 0.05). Notably, the presence of a cardiac disease history showed possible prognostic factors for satisfactorily predicting patient outcomes (p = 0.02). The presence of left atrium (LA) thrombus showed a border significant differences in comparison (p = 0.05). Although the number of patients analyzed was relatively low, our findings suggest that a history of cardiac disease is predictive of a relatively lethal or severe condition in patients with a PE. The diagnosis and prediction of outcomes for patients with a PE remains a challenge and further study is necessary in the future.