Complete left bundle branch block is an electrocardiographic manifestation in which ventricular excitation is delayed on the ECG. The true clinical significance of complete left bundle branch block is that once the block is complete, the left and right ventricular contractions become asynchronous, the ventricles contract uncoordinated, and heart failure occurs, especially when combined with organic heart disease, the ventricular wall excitation time in complete left bundle branch block can be delayed at 120-160 beats/min, or even 180 beats/min or 200 beats/min, resulting in asynchronous ventricular contractions. Ventricular contraction asynchrony can present with delayed or incomplete closure of the heart’s valves and mitral regurgitation of the atria, leading to heart failure. Uncoordinated ventricular contraction is also a form of the disease, and patients usually also present with heart failure, decreased exercise tolerance, and patients experience palpitations and dyspnea during exercise. Some patients experience recumbent dyspnea at night. In cases of coronary artery disease combined with complete left bundle branch block, this usually occurs acutely and signals the possibility of anterior descending vessel occlusion. The occurrence of complete left bundle branch block is usually an indication for thrombolysis, which may be a sign of acute myocardial infarction. Therefore, complete left bundle branch block must be treated according to the urgency of the block, the underlying pathology, and the presence or absence of heart failure.