abnormal symptoms

I am a 30 year old male, I do cardiovascular exercise 5 days per week.   Recently about 3 months ago I start having a heavy feeling in my chest and feel my chest flutter especially when I lay on my left side I can feel the flutter constantly even up near my left shoulder,   usually on my right side  I dont feel this and I can finally get some sleep.   I've noticed also that my resting pulse has dropped an average of 10 beats from  my usual 65 or so down to 55 and I've even seen it as low as 50,  I'm starting to wonder when I'm going to see it in the 40's or not soon...when it gets down in the low 50's I tend to feel a little sluggish and even dizzy.    
Do you know what any of this can mean?   I went to the doc, had an ekg, echo, blood tests and xray...normal.

[Darcy Green Conaway, MD]

Your heart rate has fallen because you are in good physical condition and that is a good thing! The heart rate alone is not necessarily concerning unless it consistently falls very low or makes you feel bad. Since you are describing feeling bad I would suggest a treadmill to evaluate for chronotropic incompetence (making sure your heart rate appropriately increases with exercise). As far as the fluttering goes, you can consider wearing an event monitor (a device which you wear for about 30 days)-- it is used to determine if your symptoms correlate with any cardiac issues, such as a very low heart rate or other arrhythmia.