I too had about a month of pulsatile tinnitus at the end of last year. I had a carotid artery duplex scan which was fine and BP was very low. It infuriated me as it kept me awake and was intrusive but, courage, it went as mysteriously as it had come and I have had no trouble since except a bit of more "orthodox" ringing in my left ear when I yawn or stretch. Liveable with.
Many cases of pulsatile tinnitus are nothing to worry about but you are doing the right thing to have further checks. If these come back negative that will help you relax and may, in turn, help you with the problem.
Good luck and let us know how you go.