I seem to be experiencing the exact same thing. The first time it occurred (around 1am I was awakened from my sleep) I was worried it was a heart attack because there was some numbness in my arms, but the incident soon passed after 5 minutes, and there wasn't any pain. Over the next couple of days, however, there was pain that sort of roamed my left chest area, and when that failed to go away, I went to the ER.
After running a couple of tests, including checking the enzyme levels around the heart and clotting risk, the ER said the cause was probably not serious. All they had found was low potassium levels.They referred me to an internist and cardiologist.
The internist was fairly convinced it was a muscular problem, but scheduled and ECG anyway last Tuesday (I'm currently awaiting results).
Since then, it's occurred twice more. Both occurred at night while I was sleeping (one episode just occurred, prompting this post). I'm fairly sure it might not be related to the potassium levels, since I took a fair amount potassium supplements today. Also my blood pressure is always normal when tested (but I must admit that I'm not sure of it's level when these episodes occur).
Does anyone have any idea? It seems my internist is clearly wrong, but it may be awhile before I can get a cardiologist appointment.
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Develop rapid heart rate while sleeping.