Does NSVT necessitate a Cardiac Cath?

Hi,
My husband has been having some dizziness when he stands from a squatting position and only then. He had an endoscopy done  not to long ago and his pulse rate was low and in the 40's. As his wife and a healthcare person I thought since he is 54 he should be worked up . So he had a stress echo and that was normal. He had a 24 hr halter monitor and the report was that they saw some irregular heart beats and dx him with NSVT. So now they want him to have a cardiac cath. I am quite upset about this. Unfortunaltely I was not at the consultation when this information was explained  to my husband. Would this be the next step or should I get another opinion? I will speak with the cardioligist about this but they are pushing to have this done.Can you help me understand this condition. Thank ou so much.