Should I have a cardiologist?

I have a 4.5 TAA that stretches from the aortic root to past the aortic arch. My PCP is monitoring it with a CTA every 6 months. He says he will refer me to someone when my aneurysm reaches 4.9 or so. I also have recently started having bouts of extreme fatigue and a pounding pulse. I will lie down and it goes away after a bit. It happens every 2-1/2 - 3 weeks. I have also begun having vague neck pain and one incident of my pulse LOUDLY booming in my left ear waking me up from sleep and resolved after about 10 minutes.

I see my PCP 09/05 and will ask these questions but I would like to know who is following everyone’s aneurysm?

Also, is the measurement of 5 set in stone or are there other variables?