If you experiencd sudden,
rapid heartbeat, events which seem to start immediately, and end in a similar fashion, you could be experiencing SVT. Supra ventricular tachycardia is often hidden and doesn't reveal itself until an event occurs. When your in norman sinus rhythm, ypur hearts electrical activity and waveform looks perfectly normal. Bodily functions like sneezing, coughing, BM's, and even passing gas cas cause sudden pressure changes within you.