anyone extra atrial contractions

From the sounds of what you are describing you are having what is known as pre-atrial contractions or PAC's.  There are several types of ectopic beats possible in the heart.  This particular one affects the upper chamber (atrium) rather than the lower chamber (ventrical.)  It is an irritable focus in your heart causing the occasional uncoordinated beat between your atria and ventricles.  Nearly everyone has an occasional innocent episode here or there if you were to look long enough, some we may feel or notice, most we won't.   1000 individual episodes in 48 hours is excessive.   All the potential factors you listed could be the etiology of the errant beat.  Do not let any of your Physicians tell you not to worry, and simply disregard this.  While it is true it may never give you any problems, it could also be cause for concern of another greater problem later on down the road.  I dont want to worry you unneccessarily, but, get it checked out fully.  My best advice is seek multiple opinons from multiple independant sources.  Your Cardiologist should repeat the Halter to compare to the previous study, perform a stress test, possibly an echo, and send you for a complete metabolic panel (blood tests.)  If a heart defect is found DO NOT PANIC.  There are many different avenues of treatment that may fit your needs.  It may be something as simple as changing your diet, or you may need medication to stabilize the irritabilty within the heart.  Other therapies exist beyond that, but no need to worry about those yet.  Take one step at a time and get your tests and full cardiac work-up done.  We all have factors that may affect our health, some we can control others we cannot, such as genetics.  My family has a predisposition to hypertension and a heart condition called PSVT which is a disorder not dissimilar to yours.  The difference is that some day my heart will suddenly jump to greater than 180 beats per minute or more without warning due to a problem with the electrical conductivity within my heart.  Once again, there are many different therapies and treatment modalities to follow.  Go see your primary care doctor for a full physical, see your cardiologist and evaluate his/her recommendations.  Don't be afraid to seek second or third opinions.  Ask questions and get informed.  Best of luck to you, I hope there is a simple explanation to your current issue, with an equally simple remedy. 

*Disclosure, I am not a physician.  I am a Fireman and Paramedic with over 13 years of patient care experience.  I've done more CPR than I can to remember and have seen way too many people let simple medical issues become larger problems.