The risk of aortic root/ascending aorta rupture or dissection increases considerably after about 5 cm at which point we recommend corrective surgery. I would recommend close follow up with your cardiologist with a repeat study in about a year. In the mean time you should be on a beta blocker regardless of your blood pressure, unless of course if it is very low.
Read my previous posts about ARBs and ACEi's with respect to aortic dilatation/aneurysms.