It is difficult to say exactly what is going on. It is normal for heart rates to get lower during sleep. However, I would not say that supraventricular tachycardia is normal. If your arm feels weak or numb, this could certainly be a sign of stroke or mini-stroke and you should seek emergency medical attention. Certain tachycardias do predispose to stroke.
I hope this has been useful. I wish you the best of luck. Feel free to write back.
Information provided here is for general purposes only. Specific questions should be addressed to your own doctor. If you would like to make an appointment at the Cleveland Clinic Heart Center, please call 1-800-CCF-CARE or inquire online by using the Heart Center website at www.ccf.org/heartcenter. The Heart Center website contains a directory of the cardiology staff that can be used to select the physician best suited to address your cardiac problem.