1.Heart auscultation: A loud and rough all-systolic murmur with tremor can be heard in the 3rd and 4th ribs of the left sternal margin. The second heart sound can be heard in the pulmonary valve area with a larger fractional flow. (2) X-ray chest film: (1) small fractional flow ventricular septal defect: X-ray shows mild increase of pulmonary texture; (2) large fractional flow ventricular septal defect: significant increase of pulmonary texture, protruding pulmonary artery segment with dilated pulmonary hilar artery, or even “pulmonary hilar dance” sign, enlarged left and right ventricles; (3) combined with severe pulmonary hypertension: significant protrusion of pulmonary artery segment, or even tumor-like dilatation; (3) combined with severe pulmonary hypertension: significant protrusion of pulmonary artery segment, or even tumor-like dilatation (3) combined with severe pulmonary hypertension: protrusion of the pulmonary artery segment, or even tumor-like expansion, the pulmonary vessels are stump-like and the peripheral vessels in the lung field are slender. (3) Electrocardiographic manifestations: (1) Most electrocardiograms of small defects are normal or have left ventricular high voltage; (2) Electrocardiograms of moderate defects show left ventricular hypertrophy and change from left ventricular hypertrophy to biventricular hypertrophy as pulmonary vascular resistance gradually increases; (3) Electrocardiograms of large defects show right ventricular hypertrophy, atrial enlargement, and right bundle branch block; (4) Patients with subseptal defects often have incomplete right bundle branch conduction (4) Patients with subseptal defects often have incomplete right bundle branch conduction block and specific ECG manifestations similar to those of endocardial cushion defects.