Goldhaber, an American, has suggested that the top 4 differential diagnoses for pulmonary embolism (PE) are myocardial infarction, pneumonia, congestive heart failure, and dilated cardiomyopathy, in that order. In this paper, the differential diagnosis of the top 4 misdiagnosed diseases (especially coronary heart disease) is made in order. Coronary artery disease Coronary artery disease presents with chest pain and tightness (angina pectoris) on exertion, and mostly shows left heart failure when complicated by heart failure, while pulmonary embolism shows exertional shortness of breath, with right heart failure predominating. Two prominent ECG manifestations may be important reasons for misdiagnosis of pulmonary embolism as coronary artery disease: ST-segment depression and V1-V6 T-wave inversion with dynamic changes in the chest leads, both seen in PE and coronary artery disease. Coronary artery disease is mostly characterized by left heart ischemic ST-T changes, evolution, and pathological Q waves on ECG, while pulmonary embolism is commonly characterized by rightward deviation of QRS electrical axis, T wave inversion in chest leads and leads II, III, and aVF, cis-clockwise transposition to V5, complete or incomplete right bundle branch block, emerging SⅠ (>0.15 mV), SⅠQIIITⅢ, or QIIITⅢ, P waves are hyperacute, and sometimes ECG changes are not typical and mild enough, or only V1-V3R-5R S waves are coarse and frustrated. Myocardial enzymes may also be elevated in pulmonary embolism, but show enzymatic changes typical of non-acute myocardial infarction. Echocardiography showing increased pulmonary artery pressure, right ventricular pressure overload, right ventricular to left ventricular end-systolic anterior-posterior diameter ratio greater than 0.5 and right-to-left diameter ratio greater than 1.0 is an important method for timely diagnosis of pulmonary embolism. For larger thrombi in the left and right pulmonary artery trunks, echocardiography can sometimes directly reveal them. McConnell et al. reported that localized abnormal right ventricular wall motion without affecting the apical portion of the right ventricular free wall is a specific sign of ultrasound in acute pulmonary embolism. In addition, further differentiation can be made on the basis of subtle differences in ECG changes between PE and coronary artery disease. Pulmonary embolism Pulmonary shadow X-ray chest radiographs may show lamellar faint shadow, wedge-shaped shadow, cord-like shadow, spherical shadow, etc., which are easily misdiagnosed as pneumonia, and the typical wedge-shaped shadow described in textbooks is not common in pulmonary embolism. The typical wedge-shaped shadow described in textbooks is not common in pulmonary embolism. X-ray signs such as pleural effusion, diaphragm elevation, sparse vascular texture in the lung field, and prominent pulmonary artery segment can also be seen in pulmonary embolism. In addition, there are obvious differences in the clinical manifestations of the two, with pneumonia mainly manifesting as cough, coughing sputum, fever, and also chest pain. Primary pulmonary hypertension (idiopathic pulmonary hypertension) Because the clinical manifestations and general laboratory test results of chronic embolic pulmonary hypertension and primary pulmonary hypertension are basically the same, the clinical diagnosis of the two is very easy to be confused. There is no obvious etiology, and the overall age of onset is early. Ultimately, it should be identified by enhanced CT, pulmonary ventilation/perfusion scan and/or pulmonary angiography. Cardiomyopathy, myocarditis Dilated cardiomyopathy or myocarditis and other types of cardiomyopathy complicated by heart failure are predominantly left-sided, with significant left heart enlargement and progression to total heart failure; it is rare to have significant pulmonary hypertension and right heart failure without significant changes in left heart function. Right ventricular cardiomyopathy is often associated with arrhythmias, mostly in young and middle-aged people, with palpitations, dizziness or syncope during exercise or emotional excitement as the main complaints. Pulmonary embolism, on the other hand, is characterized by right heart failure as the main clinical manifestation.