heart failure
"I was exhausted and constantly gasping for breath.  My cardiologist put me on isosorbide mononitrate, one pill a day.  The difference was astounding.  I no longer was gasping for breath and no longer had to take naps.  The pill would wear off during the night so the doctor recently changed me to two/day.  Am experiencing some pretty severe headaches and dizziness when get up to fast.  Doctor had told me I would experience headaches but they would go away eventually."