First of all, the prognosis
is very good, and that is most important. Yes, anxiety
can cause a tachycardia and arrhythmias, so if your internist does not have any other physiologic reason for the tachycardia, that is the best bet. Regarding sleep, yes, it can definetly wake you up, just like a scary nightmare can wake you up with a tachycardia, here you have the effect without any memory of the image that caused it.