The severity of left bundle branch block depends on the cause of the left bundle branch block. If there is no organic heart disease, it is usually not serious, but if there is a combination of severe coronary artery stenosis, myocarditis, and cardiac insufficiency, it suggests a more serious condition. Normally, electrical activity of the heart is emitted from the sinus node, conducted through the interjunctional bundle to the atrioventricular node, then through the Hitchcock’s bundle to the left and right bundle branches, and then to the ventricular myocytes through the Purkinje fiber network. When structural or other changes occur in the left bundle branch, its conduction slows down and left bundle branch block occurs. Organic heart disease can cause left ventricular hypertrophy and ischemia, the left bundle branch is pulled by the left ventricle and damaged or broken, resulting in left conduction block, and in severe cases, chest pain, shortness of breath, palpitations, dizziness, and edema of the lower extremities, etc., and there are no obvious symptoms in those without organic heart disease changes. In the case of left bundle branch block, the heart has a compensatory function and can transmit current through the right bundle branch to fulfill the physiological function of the heart. If left bundle branch conduction block occurs, it is necessary to consult a doctor in time, under the guidance of the doctor for examination, to find out the cause and treatment.