subtle septal wall defect

I had a chemical stress test and the doctor said it was a little abnormal and wanted me to go into the hospital the next day for a heart cath.   All he would tell me was that I had a slight abnormal report.   After 3 weeks I get a partical report that says everything is normal except the resting images showed a subtle septal wall defect which partially reversed on resting images.  His conclusion Mild reversibility noted in the septal wall. Clinical correlational required.    Note: I have severe emphysema.   My doctor would not explain anything.

In plain ENglish, what does this mean and is it a serious thing?

THank you,
Kaylena