I believe that you are correct in assuming that the bigeminy is either caused by or aggravated by low blood oxygen levels. Hypothyroidism and B-12 deficiency could all play a role. Each of these is treatable and correctable and to do so is important, independently of their possible effect on your heart rhythm.
An oxygen saturation of 72% is indicative of significant oxygen deprivation. If not already prescribed, you should be using supplementary oxygen, definitely during sleep and most likely, continuously, 24 hours a day. Also if the cause of the low oxygen, other than that attributable to sleep apnea, has not adequately been determined and treated if treatable, that too should be done without delay.
“How long can I live?” That is impossible to say and may continue to be impossible after your oxygen deprivation is corrected.
Good luck
Thank you so much! every morning I have been struggling to awake because I am so extremely swollen. My eyes swollen shut, my fingers so swollen they are shiny, headaches....I feel awful upon awaking. I will be headed back to the doc very soon and will be tested for hypoxemia and I believe he will be sending me out for another sleep study as an update as he mentioned before. Thanks again so much for taking the time to answer my question Dr Tinkelman =]