Racing heart rate

Hi Doctor.  Thank you for this forum.
In the last week, at two seperate times, my heart rate started racing for no apparant reason.  Both times I was sitting still, at rest.  My heart rate had about 12-15 beats real fast, then when back to normal.
I've seen a cardiologist in the last year for irregular heart beats and had a angiogram and a stress echo.  He has told me that my heart is normal and that my arteries are wide open.
This racing heart rate occurance is new.  I am telling myself it is nothing to worry about, but I wanted to run it by you and see what your opinion is.
Thank you.

[CCF CARDIO MD JMF]

Dear Don,

I would recommend a holter monitor to characterize the frequency and cause of these beats. It is likely that this is nothing to worry about but important to know that for sure.

[ELLIEMAERUS]

A related discussion, RACING HEARTBEAT CAUSES was started.