@ashred The heart reacts to how well or poorly the lungs may be working, and the heart beat will increase if the lungs are not efficiently absorbing oxygen. This has happened to me because of excess phlegm that seemed to come from an infection. I went to the ER with a resting heart rate over 100 and they said it was bronchitis. A course of antibiotics fixed it and I was able to get rid of the phlegm from the infection and return to normal. I also have a physical problem in that I have thoracic outlet syndrome that makes one side of my chest too tight, so my left chest doesn't expand as much contributing to the problem. I have had ribs twist and pop out of position from TOS and work with a physical therapist who can resolve this. I have had chest pains when this happens or from extreme stress. That might be food for thought to see if allergies or a possible lung infection may be contributing to the issues of shortness of breath and affecting the heart.