In diagnostic work-up for pulmonary stenosis (PS), cardiac catheterization generally is not needed to verify the findings of noninvasive tests (such as Trans esophageal echocardiography), except when a significant discrepancy is noted between clinical findings and echocardiographic findings. When performed, cardiac catheterization can diagnose PS by a pressure gradient from the pulmonary artery to the right ventricle on "pull-back" of the pulmonary artery catheter. Cardiac catheterization may be useful in assessing the presence of concomitant congenital abnormalities. So, findings of cardiac catheterization may be taken as diagnostic of PS. 

On the other hand, in the case of isolated Peripheral PS, pulmonary angiography may be needed to establish the diagnosis.

Ref.: Ren et al. Pulmonic stenosis. [Internet Article on Medscape].  http://emedicine.medscape.com/article/157737-workup#showall

indication of catheterisation over TTE specially needed in cases of severe pulmonary stenosis or atresia with collaterals and also to detect peripheral pulmonary artery stenosis. class I ACC AHA recommendation for PBV is1) asymptomatic 60 and symptomatic 50 mm Hg peak instantaneous gradient2) Asymptomatic 40 and symptomatic 30 mmHg mean doppler gradient

with less than moderate PR .

Plesae, see the following article which would be helpful in your case: 

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3611114/

for isolated PS diagnosis, cardiac catheterization is not required. Even TEE is not required. TTE is enough.