An infant with a large VSD will fail to thrive and become sweaty and tachypnoeic (breathe faster) with feeds.The restrictive ventricular septal defects (smaller defects) are associated with a louder murmur and more palpable thrill (grade IV murmur). Larger defects may eventually be associated with pulmonary hypertension due to the increased blood flow. Over time this may lead to an Eisenmengers syndrome the original VSD operating with a left-to-right shunt, now becomes a right-to-left shunt because of the increased pressures in the pulmonary vascular bed. Cause
Congenital VSDs are frequently associated with other congenital conditions, such as Down syndrome.A VSD can also form a few days after a myocardial infarction (heart attack) due to mechanical tearing of the septal wall, before scar tissue forms, when macrophages start remodeling the dead heart tissue. A congenital VSD can result from a disturbance in the morphogenesis of the heart in its embryonic stages. In the fifth week of gestation, the heart undergoes multiple processes of septation and forming a dextral loop. Interfering with the latter leads to insufficient leftward movement of the ventricular outflow tract over the atrioventricular canal, which in turn can result in a VSD or, in the most extreme cases, a double outlet right ventricle with one.A ventricular septal defect arises when the superior part of the interventricular septum, which separates the right and left ventricles of the heart, fails to fully develop.
Auscultation is generally considered sufficient for detecting a significant VSD. The murmur depends on the abnormal flow of blood from the left ventricle, through the VSD, to the right ventricle. If there is not much difference in pressure between the left and right ventricles, then the flow of blood through the VSD will not be very great and the VSD may be silent. This situation occurs a) in the fetus (when the right and left ventricular pressures are essentially equal), b) for a short time after birth (before the right ventricular pressure has decreased), and c) as a late complication of unrepaired VSD. Confirmation of cardiac auscultation can be obtained by non-invasive cardiac ultrasound (echocardiography). To more accurately measure ventricular pressures, cardiac catheterization, can be performed. Classification
Although there are several classifications for VSD, the most accepted and unified classification is that of Congenital Heart Surgery Nomenclature and Database Project. The classification is based on the location of the VSD on the right ventricular surface of the inter ventricular septum and is as follows:

Multiple
Type 1
Type 1 is sub aortic

Type 2
Type 2 also known as perimembranous, paramembranous, conoventricular, membranous septal defect, and subaortic. Most common variety found in 70%

Type 3
Type 3 also known as inlet (or AV canal type). Commonly associated with atrioventricular septal defect, found in about 5%

Type 4
Type 4 also known as muscular (trabecular)

Located in the muscular septum, found in 20%.