Small pulse pressure is caused by reduced elasticity and compliance of the peripheral blood vessels. Reduced vascular elasticity is mainly caused by the presence of large deposits of lipids and calcium salts under the intima and hyperplasia of the smooth muscle layer in the intima. When the pulse pressure is low, in addition to the blood vessel examination, a cardiac sonogram is also performed in the clinical setting. The method of recording the vibrations generated by the heart during its activity through a special electronic instrument called a cardiogram machine, which changes the vibrations into line drawings from the chest wall, is called a cardiogram, and the recorded drawing is a body surface cardiogram, or a cardiogram for short. It can assist in the diagnosis of certain cardiovascular diseases and identify some intracardiac diseases with similar body surface murmurs but different lesions, such as coronary artery disease (changes in the 4th heart sound – S4 before and after exercise), estimation of mitral stenosis, pulmonary valve stenosis (valvular or funnel section), arteriovenous catheterization and distinction between main pulmonary artery defects, etc. 1. Precautions: Quiet must be maintained in the laboratory. The patient must eliminate tension and quietly cooperate with the medical staff to complete the examination. 2.Examination procedure: The examination is performed by a specially designed electronic instrument, i.e., a heart sound machine. 3.Indicator interpretation results: Normal The first heart sound (S) is equivalent to 0.02-0.04 seconds after the start of the QRS wave on the ECG, accounting for about 0.08-0.135 seconds. It is caused by ventricular contraction, mitral valve closure, and tricuspid valve closure with ventricular contraction when blood flow enters the great vessels. The second heart sound (S) is equivalent to the end of the T wave on the ECG. It is caused by the vibration of the ventricular wall during ventricular diastole, the closure of the aortic and pulmonary valves and the opening of the atrioventricular valve when blood flows from the atria into the ventricles. The third heart sound (S) is equivalent to the distance from S after the T wave on the ECG of 0.12 to 0.20 seconds, accounting for 0.05 seconds, with low frequency and amplitude. It is caused by the rapid filling of the ventricle and the vibration of the ventricular wall. The fourth heart sound (S) is equivalent to 0.18 to 0.14 seconds after the P wave on the ECG, with low amplitude, and is caused by rapid blood flow into the ventricle during atrial contraction, which vibrates the ventricular wall.