irregular heartbeat

I am a 42 year old male who has recently experienced some chest pain and pressure along with an irregular heartbeat.  I also have tenderness in my ribs right below my heart.  I have had an echocardiogram which was normal, as well as a stress test that was fine.  To regulate my heartbeat I am taking Cardizem (120mg)
and after my last episode I was also put on Naproxen(500 mg) for 10 days.  I still am feeling tired,lethargic,and lightheaded. The irregular heartbeat has decreased in frequency down to about 14 per 24 hours but the pain is still there and my cardiologist seems to feel that because of my test results that this may not be heart related.  I do have a thickened mitral-valve but my doctor does not seem to think that this is the problem.  Just wondering if you have any comments concerning this problem. Thank you for any information that you can provide me with.

[CCF CARDIO MD JMF]

Dear Kurt,

could you please clarify what your doctor told you your irregular heart beat was from? atrial fibrillation or PAC's and PVC's?