I think you should get a second opinion and if your worried talk to the doctor and ask him why he hasn't put you on medication at least as a prevention because I think three years is pushing it.
Pheles
By the way I have had cronic hypertension since the age of 9 and can not beleive that you doc hasn't put you on something.
What was your pulmonary pressure on the cardiac cath? You definitely need to be seeing a PH specialist and not just a cardiologist. If you had an ASD closure already that complicates the situation. If your pulmonary pressures are elevated now due to left heart problems, you could have serious problems if you are put on a med specifically for PH caused by right heart problems. Sometimes you might have to travel a couple of hours to find a true PH specialist but you do need one for sure. Try phassociation dot org, then click on newly diagnosed and then find a doctor. Good luck.