Attacks could last minutes or hours and
any combination of symptoms would happen. And
attacks, my heart would regularly do many strange things - tachy, brady, irregular rhythm, extremely forceful beats, 'flip-flopping' feelings, etc.
I also sometimes experienced a sensation of the heart stopping and restarting - immediately after the restart I would feel a MASSIVE, uncomfortable surge of adrenaline and the heart would beat very fast for a little while.