Dear Irene,
I am sorry to hear about your recent symptoms of shortness of breath and chest discomfort. Mild tricuspid regurgitation and mild mitral regurgitation are very common in the general population and are very unlikely causes for your symptoms. It is possible that your pneumonectomy could be playing a part in your symptoms. However, I would ask your doctor whether or not your pacemaker's rate increases sufficiently when you exercise. Also, blockages in the heart arteries may cause similar symptoms and a stress test may be warranted. I would recommend seeing your cardiologist and discussing your symptoms along with the issues mentioned here. Hope this helps.
Thanks for your question,
CCF-MD-KE