Background: Clinical manifestations of acute pulmonary embolism (PE) vary widely, making it challenging to diagnose. Differential diagnosis is crucial in patients with right ventricular (RV) pressure overload and dyspnea. Transthoracic echocardiography (TTE), although not the gold standard for PE diagnosis, is a valuable tool in differentiating PE in patients with dyspnea, such as pulmonary hypertension (PH), in real-world practice. Methods and Result: Between 2012 and 2019, 269 patients were enrolled based on specific criteria: 1) pulmonary artery systolic pressure >40 mmHg by TTE, 2) PE confirmed by chest contrast CT, and 3) TTE and CT conducted within a 72-hour interval. The study population was categorized into two groups: PE (n=149) and Non-PE (n=120). In the mitral inflow Doppler parameters, the PE group exhibited significantly lower mitral E velocity. The cutoff value of mitral E velocity (AUC 0.865, 95% CI 0.81-0.92, p<0.001) for diagnosing PE was 0.735 m/s (sensitivity 0.700, specificity 0.839, positive predictive value 77.36%, negative predictive value 76.36%). Conclusion: This study suggests that mitral E velocity is an independent predictor for diagnosing PE. The cutoff value of mitral E velocity is a practical tool for ruling out PE in patients with PH in real-world practice.