lanna,
To give some insight, one can have a heart attack (MI anterior infarct, heart muscle damage) and not have any symptoms or have had symptoms that were temporary. If untreated from an MI, the heart will eventually fail or cause arrhythmia. Normal blood count helps determine if there was heart damage within the last few hours or so..
Peripheral edema can be due to the heart's right side failure to pump the blood received from the vessels to the lungs. This can cause fluids to back up and leak into the tissues. Usually, right-side failure involves edema to both legs and abdomen. One leg edema could be caused by a blood clot?!
You should verify if there is or is not and what degree of heart muscle damage if any.
Did the ER do a blood test for cardiac enzymes? That is one test for an MI that tells the whole story, if done quickly enough. There are 3 blood samples taken at 8 hour intervals. The first one is usually slightly elevated. The second one is higher, and then it drops, as the third one usually indicates.
When you have this type of pain, you really need to go to the ER immediately, and do not drive but call an ambulance.