Dear middenjm,
The symptoms that you describe (i.e. the sensation that your heart is skipping, shortness of breath) can be caused by an irregular heart beat or extra heart beats, commonly called prematuure atrial or ventricular contractions (PAC's or PVC's). However, it sounds lik you have had a thorough cardiovascular workup looking for a heart related cause of your symptoms. It is less likely that the feelings you describe are related to your heart since your EKG, echocardiogram, and stress test, and blood work are all normal. There is a small possibility that you may have periods of irregular heart beats or extra heart beats that were not seen at the time of testing. For this a 48 hour holter monitor might be an option. This type of test monitors your heart beat for an extended period of time and woudl be more likely to capture any extra beats if they tend to occur only in brief episodes. In addition to 48 hr monitoring, there are other types of extended heart monitors that you can ask your doctor about. There is always the possibility that these symptoms are not related to your heart, particularly if your testing and heart monitor are all normal.
I get heart beat skips to and mines from an anxiety disorder tht i piked up a year ago from a stressful period of time