Aneurysmal Atrial Septum

I am a 50 yo male in good health, exercise daily, trail runner, have had an exercise intolerance, i.e. shortness of breath and "out of gas" feeling during high levels of exercise.  I can tolerate a high intensity walk on a treadmill--say 2 hours at 15 degrees, however, if I try to run for a mile, I get short of breath and out of gas.  Having trouble deciding if this is physical or mental.  I am a cardiac sonographer and during a product demo, it was realized that I have an aneurysmal septum, and a pfo was present during the echo.  Could the aneurysmal septum become even more mobile during high exercise loads thus increasing the flow across the septum?   The right side of the heart looked normal, but I did have possibly more than trace or even mild pulmonary regurgitation.  Rt sided pressures were not acquired.