<s>[INST] Hello, I am 59, weight 159 lbs, moderately active.  I have a very low pulse rate (around 45).  I getdiscomforting pain (not overly sharp or stabbing, but still more than a mild discomfort) on my left side and upper back.  I get it only when I lie down and only when I breatheout.  It goes away if I breathe in and hold my breath.  It eventually subsides. [/INST] Hello, I have gone through your query. Thanks for using Chat Doctor. Your low heart rate may not be related to your chest pain. You must get one Resting ECG to determine type of rhythm you have. Depending upon on your baseline ECG you may need exercise stress testing to rule our blocks in heart arteries causing chest pain. If your heart check up turns to be normal you should consult a physician to evaluate you for acid reflux and any other cause of your pain, My best wishes Chat Doctor.  </s>