It is very common to find low voltage in the thoracic leads when examining ECG, especially in some patients who are obese, because of more subcutaneous fat. If the patient is obese but has no other clinical symptoms, it usually does not matter. Patients suffering from other diseases may also cause low voltage in the thoracic leads, such as patients suffering from coronary atherosclerotic heart disease or rheumatic heart disease, which may lead to heart failure and thus pulmonary edema, and may also have low voltage in the thoracic leads when the ECG is examined, but it is usually accompanied by other ECG abnormalities. Other diseases that cause pleural effusion may also cause low voltage in the thoracic leads. In order to make a definite diagnosis, it is necessary to improve the relevant examinations according to the clinical symptoms of the patient, and if other diseases cause low voltage in the thoracic leads, it is necessary to carry out targeted treatment according to the cause.