The heart stun technique was an arcane skill practiced by the Sith. This technique, when implemented properly, halted the heart's beating, allowing the organ to maintain a type of stasis. The idea was to allow for a Sith to capture a target without having to engage them in battle. It had been rumored that Count Dooku used the heart stun technique to keep General Grievous alive after the wreck of the Martyr. Also Darth Maul used this technique on a Moorjhone elder who had discovered Maul's true identity, only at a more fatal level.