Is Nirvasc Advisable For A Child With Aortic Stenosis?

My 12 year old son has aortic stenosis, mitral valve regurgitation, hypertrophic cardiomyopathy, AV block type 2, LVH, and asthma! The only medicine he is on is Lisinopril 5 mg! He is very symptomatic! I just talked to his cardiologist and he wants to switch his medicine to Nirvasc because the other morning he had chest pains and his blood pressure was 178/118 and he of 122. Today it is 147/91 hr 118. I am worried because it said something about taking this medicine with aortic stenosis. He also has a lot of fluid in his feet.