Hello...
I'm wondering how you know for sure that you have been in asystole...Has this been seen on an EKG or another form of monitoring? Since your question is "what's wrong with me?" I gather that you haven't seen a Dr about this or been yet diagnosed with an arrhythmia. This needs to be addressed ASAP!
Do you have any other cardiac related history?
I would most defiantly see a doctor about this, if you can not see one right away, maybe a trip to the ER would be helpful.
Have you seen a Dr about this?
I think you should consider seeking medical help/advice.