The alternating pulse is a pulse with regular rhythm and alternating strength and weakness, caused by alternating strength and weakness of the left ventricular contraction, if necessary, the patient is asked to hold his breath in the middle of expiration to exclude the possibility of respiratory changes, as one of the important signs of left heart failure, severe myocardial damage, seen in hypertensive heart disease, acute myocardial infarction, etc. X-ray examination of the enlarged heart shape, predominantly left heart, and pulmonary stasis suggests Left heart failure. The common tests for alternating veins are as follows: I. X-ray The enlarged heart shape, mainly the left heart, and pulmonary stasis suggest left heart failure. ECG A positive P-wave terminal vector (PtfV1) in lead V1 of ECG is a common and important indicator for the diagnosis of left heart insufficiency. In addition, ECG has specific diagnostic value for the diagnosis of digitalis toxicity, paroxysmal tachycardia and atrial flutter. Echocardiography Left ventricular enlargement is the main cause of left ventricular enlargement, and the decrease in the volume per beat (SV) and cardiac output (CO), and the decrease in the ejection fraction (EF) <0.50 indicate left heart insufficiency. Radionuclide and magnetic resonance imaging can measure end-systolic diastolic volume and ejection fraction of the left ventricle. V. Traumatic hemodynamic examination The floating catheter can measure pulmonary capillary wedge pressure cardiac output (CO) and cardiac index (CI), which are important indicators for the diagnosis of left heart insufficiency.