It is not always a question of whether one can do something about a disease or not but also the disease merits anything to be done about it. A 50% blockage in the aorta, merits no treatment because it is not a flow limiting lesion. All that one should do by way of treatment is risk factor control so that disease does not progress any further but 50% blockage does not cause any restriction of flow to the organs of body that it is destined to supply and hence it doesn't call for any treatment. Certainly endovascular grafts can be placed to open that blockage but when a treatment is not indicated, it shall not be provided. I think your cardiologist is justified in saying that it needs no treatment but I don't think the wordings is correct that nothing can be done about it. You can log on to google search and type Aorta and Blockage as key words and you would have 100 of sites where you can read about the treatment for blocked aorta.