Diltiazem is the main ingredient of Hexinxiao, the effect of lowering the heart rate varies from person to person, and the dosage of the drug should be adjusted gradually in the process of taking the drug. Diltiazem is a calcium antagonist, in the dilation of blood vessels to improve myocardial blood supply at the same time, can play the effect of slowing down the heart rate, clinically can be used in the treatment of tachyarrhythmia, such as sinus tachycardia, paroxysmal supraventricular tachycardia, and so on. The effect of the drug varies from person to person and is related to the patient’s response to the drug, some patients are sensitive to the drug, after taking the drug can appear stable effect, a small number of patients are sensitive to the drug, a larger dose may not be able to play a significant effect. Adverse reactions of Diltiazem include dizziness, bradycardia, dyspnea, skin itching, dry mouth, constipation, dyspepsia, etc. It is contraindicated in severe bradycardia, allergy to the drug components, morbid sinus node syndrome, second and third-degree atrioventricular block, hypotension, and pregnant and lactating women. Fast heart rate patients in the control of the heart rate at the same time, but also to find the cause of the primary causes of rapid heart rate, active treatment of primary diseases, while under the guidance of the physician to give symptomatic treatment.