How serious is subaortic vsd (1.1 cm)? The mitral and tricuspid valves show redundant leaflets with evidences of prolapse and the left ventricle is slightly dilated.

May need surgery. Typically, a 1.1 cm diameter vsd will need surgery in the first few months of life. However, in high quality pediatric heart surgery programs, the risks of repair of an isolated vsd are low and the long-term outcome should be excellent.
Probable for surgery. A vsd that size may cause lv overload, which would need anticongestive meds & might need surgery-->lv enlargement would be unsurprising. We will often wait to see if a vsd will shrink or close on its own, but a subaortic vsd may distort the aortic valve, causing aortic prolapse & regurgitation (bad problems). Often will require earlier surgery to protect aortic valve. Close follow up is important.
Requires surgery. Assuming we are talking about an infant: a vsd of this size is large enough to warrant open heart surgical repair in infancy. Dilation of the left ventricle with congestive heart failure due to pulmonary over-circulation is expected. If it is repaired early, it is hoped that the effect on the valves will be minimal, and there should be a good prognosis.