I have muscle weakness, fatigue, and shortness of breath when exercising or going up a flight of stairs. I am taking medicine for high blood pressure, acid reflux, and cholesterol. I have one stent in my heart blood vessels and have a pace maker implanted. I had a stress test which showed a shadow on the lower vessels of my heart, but a heart catherization today showed the blood was flowing well through my heart and to my body. What else might be causing these symptoms?