Doctor Please Let Me Explain: I Am An 87 Yr

Doctor please let me explain: I am an 87 yr old male with Afib although my cardiologist says it is Aflutter as the ventricular rate u sually doesn't go above about 70BPM when the episode occurs which is every few days
when i can usually end it in about 4 to 5 hrs with 150mls of flecainide - orally ~
My problem is - and has ben for about 9 yrs is that I suffer from light headedness accompanied by a sick feeling that i would describe as a malaise ! Please note that I have had Echograms, Event Monitors and so many checks for possible causes that I can no longer remember each one - al lto no avail !
Let me offer that my thyroid T4's are at the lower end of the scale with the TSH's more than double the reference levels however; when I take about 0.25 of Synthroid it ccauses my Afib or flutter to worsen which makes the lightheadedness and malaise even worse !
Let me add that I have had a pacemaker for about 17 y rs - recently replaced with a Biotronik - German sourced!
So, my problem is: i have had this lightheadedness and malaise for about 9yrs now which robs me of the quality of everyday life Beause of it I'm unable to function very little without lying down to rest even though I'm not short of breath !
The electophysiologists say they can offer nothing as they have provided the Flecainide and Deltierzem that controls the Aflutter - or fib however it may be defined !
I am inclined to wonder if the Afib is confined to the Atria - not getting through the node intothe ventricle only when the episoders show up by the way I feel and shown on the monitor with BPM of 70 - 80 ??
Any thought or comment on this that you might offer , I would deeply appreciate it as it is a virtual scourge taking away the quality of life for me during the last almost 9 yrs - with no help forthcoming !!
Stan burnham
I thank y ou inadvance !