First we need to understand how a heart murmur is produced? Generally speaking, murmurs occur when the blood in the heart flows too fast or with too much force between the parts of the heart and vibrates against the walls of the heart or the walls of the blood vessels. In addition, murmurs can occur when the normal channels between parts of the heart become too narrow or when there are abnormal channels in the heart that create abnormal “eddy currents” when blood flows through them. There is also a distinction between normal and abnormal murmurs that occur after heart surgery. The so-called normal murmur, which is bound to appear after certain surgeries, does not affect the correction of deformities and the recovery of heart function. 1, after surgery for valve disease. The most common is pulmonary valve stenosis, these children due to the thickening of the valve, fusion, resulting in narrow pulmonary artery outlet, surgery will be fused valve cut, the blood can be unobstructed. However, the thickening of the valve cannot be changed immediately; the valve after cutting will not be smooth and sealed like the normal valve part, so the blood flow through the valve will also produce a murmur, but this murmur will gradually become lighter with the growth of time after surgery. 2, due to intracardiac patch. The patch material is mostly pericardial or artificial, and the position of the patch can affect the blood flow and produce small eddies around the patch, which in turn produce a certain murmur. It is most common in the repair of subpulmonary septal defects. Reconstructed flow pathways are common in patients with complex precordial disease, such as pulmonary atresia, which requires the creation of a vascular bridge between the corpora arteriosa and pulmonary arteries and produces a murmur when blood flows through. A murmur may also occur in patients with tetralogy of Fallot with an enlarged right ventricular outflow tract due to pulmonary artery regurgitation. Abnormal murmurs are seen in the following conditions. 1. post-operative residual shunts, which produce an abnormal “vortex” of blood flow through them, resulting in a murmur. 2, residual obstruction after surgery, such as right ventricular outflow tract stenosis or obstruction patients, stenosis or obstruction is not completely lifted, blood flow through too fast, there will be murmurs. 3, valve stenosis or incomplete closure, most commonly in valve disease, valve plastic surgery, if there are still different degrees of stenosis or incomplete closure, will produce systolic or diastolic murmurs. Warm tip: The murmur produced after cardiac surgery is not necessarily abnormal. Doctors can often clarify whether the murmur is normal or abnormal through cardiac ultrasound or cardiac catheterization.