A ventricular septal defect (VSD) is an opening that exists between the two lower chambers of the heart. Some of the blood returning from the lungs and into the left ventricle flows to the right ventricle through the hole instead of being pumped into the aorta. Because the heart has to pump extra blood and is overworked, it may enlarge.
If the opening is small, very little extra blood is pumped to the lungs, and the left heart is nearly normal in size. In that case, the only abnormal finding is a loud murmur typically heard in a VSD. These small holes are usually left alone unless they cause other problems with the heart due to their location (some holes are close to the aortic valve and may suck the leaflet into the hole causing progressive leakiness of the aortic valve).
If the hole is large, a lot of extra blood is pumped to the lungs and back to the left ventricle so that the left ventricle is enlarged. Also, with larger holes, the pressures in the left and right ventricles become equal. In infants and children with large holes, symptoms develop such as breathing quickly, sweating with feeds, poor growth or exercise intolerance. Medications may help with these symptoms and give the time for the hole to close or get smaller on its own (50% of VSDs close spontaneously), but with a large hole, closure is usually recommended. If large holes are untreated, the large amount of extra blood and the elevated pressures in the lungs causes injury to the small arteries going to the lungs known as pulmonary vascular disease. Sometimes this is reversible, but after many years, it becomes irreversible and causes Eisenmenger syndrome.
Heart with Ventricular Septal Defect