Questions about example sentences with, and the definition and usage of "Ventricular"

A: × Ventricular septal defect (VSD) is the most common congenital cardiovascular anomalies that the interventricular septum (the wall between two ventricles) has a hole, resulting in a shunt (an abnormal blood flow) between ventricles.
✓ Ventricular septal defect (VSD) is one of the most common congenital cardiovascular anomalies, in which the interventricular septum (the wall between the two ventricles) has a hole, resulting in a shunt (an abnormal blood flow) between the ventricles.

× In VSD, since the blood in the left ventricle flow into right ventricle, the pulmonary blood flow will increase and lead to expansion of the pulmonary artery, left atrium and left ventricle.
✓ In VSD, since the blood in the left ventricle flows into the right ventricle, the pulmonary blood flow will increase and lead to expansion of the pulmonary artery, left atrium and left ventricle.

× In long term, this shunt result in pulmonary artery hypertension, elevated pulmonary artery vascular resistance, right ventricular pressure overload, and right ventricular hypertrophy.
✓ In the long term, this shunt results in pulmonary artery hypertension, elevated pulmonary artery vascular resistance, right ventricular pressure overload, and right ventricular hypertrophy.

× Eisenmenger's syndrome occurs when the shunt direction is reversed (the blood in the right ventricle flow into left ventricle) because of the continuance of pulmonary artery hypertension.
✓ Eisenmenger's syndrome occurs when the shunt direction is reversed (the blood in the right ventricle flows into the left ventricle) because of the continuance of pulmonary artery hypertension.

× The blood which is not oxygenated circulate through body so that the patient will have hypoxemia including dyspnea, cyanosis and nail clubbing.
✓ The blood, which is not oxygenated, circulates through the body, causing the patient to have hypoxemia including dyspnea, cyanosis and nail clubbing.

× The VSD patients with Eisenmenger's syndrome have poor prognosis.
✓ VSD patients with Eisenmenger's syndrome have a poor prognosis.

× For the treatment of VSD, the patients will be administered diuretic or take surgery.
✓ For the treatment of VSD, patients will be administered a diuretic or receive surgery.

× However, the patients with small defect do not need treatment; some of hole can be naturally close.
✓ However, the patients with small defects do not need treatment; sometimes the hole can naturally close.

You seem to have a very high level of understanding already, so I tried to make as few changes as possible.