Since your baby is only 20 days old, it is too soon to know if surgery will be required. A 6 mm posterior muscular VSD is moderate to large in size, so in the next month or so there could be signs of too much blood flow going across the VSD and out to the lungs: symptoms like breathing fast, not feeding well or not gaining weight well. If the VSDs are truly muscular types, they can decrease in size over time. The decision to do surgery in this case requires watching the baby's feeding and growth and rechecking to see if the VSD is getting smaller by echo. So this should be checked again by the cardiologist between 3 and 6 months of age. If the baby starts to develop the signs I mentioned, the doctor may decide to use a diuretic medication to help relieve the symptoms and give the baby more time to grow and see if the VSDs can get smaller on their own. Surgery is reserved for children who are failing to thrive, or have high pressure in the lungs. The doctor will be able to tell you about the lung pressure from examination and the echocardiogram. Good luck.
thank You Sir