Due to high blood pressure and irregular heart beat, I have to have a heart scan in a few weeks. Can still I use treadmiill for 30mins every two days?

I would urge. You to postpone the treadmill until you are cleared by your cardiologist. The added stress could exacerbate your heart irregularities or elevated your blood pressure further.
If you are. Exercising on the treadmill at this moment for 30 minutes without any symptoms keep doing it. Now, I am sure your cardiologist or primary care doctor already know you are exercising. If you are talking about starting treadmill exercise now, i will advised to wait until the studies and evaluation finish. Good luck.