A heart catheterization is a heart test that is done by a cardiologist with the help of one or two technicians. Soft, thin plastic catheters are placed in the large blood vessels in the leg and threaded carefully to the heart. In this way, pictures of the heart can be taken and pressure measurements inside the heart's chambers can be made. Overall, this is a very safe test and children usually go home the same day. In Zachary's case, we were admitted to the hospital after the cath since his surgery was scheduled the next morning.