Enlarged heart valve in a 6 year old?

We took Nic to the doctor on Wed. He has bronchitis, but they did an xray to rule out Pneumonia. Last night he got really really pale and had really dark circles under his eyes, so i called Dr. Coward this morning. They called to get the radiologists full report from the x-ray and saw a "prominent pulmonary outflow" (i have no idea what that is) but they wanted him to go to the hospital and get a CT scan of his chest . They called this afternoon and told me that he had an enlarged valve in his heart. We have to call monday to schedule and appointment with a cardiac cardiologist to see if he has Heart Valve Disease. can anyone tell me what this means??? is surgery common??? He does get winded easily when playing and occasionally complains of dizziness, but not on a daily basis....any info is appreciated!