Yes, I Have Pacemaker That I Have Had For 5

Yes, I have pacemaker that I have had for 5 years. I have periodic but very significant shortness of breath especially when climbing stairs but sometimes I am just walking and become short of breath.
I have seen electro-cardiologists, had stress testes etc and no definitive answers. I should mention that I have always been active and continue to work out every most days.