hi there, i am a 24year old female, i been experiencing sudden onset of palpitations that can last anywhere between 15minutes-a few hours. they make me feel dizzy, nausea, SOB and once resolved im feeling exhausted for a few hours. iv been to a cardiologist who put me on a holter monitor for 3 weeks but nothing showed up. i was recently taken to hospital for the palpitations but it only showed a sinus tachycardia of 145bpm. i was not anxious infact i get palpitations like this randomly i could be resting or at work. my grandmother and my uncle had cardiac ablasions for palpitations like mine, unfortunatly they are unable to remember the name of the arrhythmia they had. my cardiologist says to just take Propanolol when they come on to help bring down my heart rate otherwise the cause at present is unknown. what could be causing me to experience palpitations? i am one to beleive there is a cause for everything..