For the past month I've been experiencing a cough, occasional palpitations, and sometimes having trouble taking very deep breaths and upon Googling (not the best idea, i know) I saw that congestive heart failure was a possibility. I was also born with Pulmonary Stenosis and am overweight. I went to the doctor today and he listened to my lungs and said they sounded great and he did an EKG which came back normal. I read online though that EKGs can miss heart failure. What are the chances of that?