Willie,

Thanks for your question. 

With your history of supraventricular tachycardia (SVT) and two ablation procedures, you have to assume that any palpitations lasting more than a few minutes may be a recurrence of the arrhythmia.  You need to contact your doctor for an appointment to let him/her know of your symptoms.  If you are on medication, they may want to adjust the dosage, or they might request further studies. 

Why you're having these symptoms at 4:30 a.m. is unclear.  One explanation is that you are in a lighter sleep pattern at this time, and therefore the palpitations can awaken you more easily than the first few hours of sleep.  The panting could be secondary to the arrhythmia. 

If your doctor determines that this is not your SVT, then he direct his attention to other possible causes for your symptoms.

Best wishes.

Martin Cane, M.D.