I had open heart surgery 8 years ago, I used to have AFIB but a valve replacement resolved it so far. I also have sleep apnea and use a cpap. Recently I have been getting up in the middle of the night once or twice to urinate and I am experiencing shortness of breadth. After I urinate it goes away. What could be causing this shortness of breadth? It seems to have gotten worse over the last couple of months