I think what you are asking is how long you'd still be conscious if your heart were instantly removed a la Apocalypto or that Indiana Jones movie with the human sacrifice. There were experiments conducted with those who were beheaded by a guillotine, coming out to something like 30 seconds consciousness post-separation to the extent that the disembodied head would react to stimuli. This situation doesn't really apply to heart removal. Keep in mind, there are people who have lived with a still heart, surviving solely on the muscle contractions of arteries to circulate blood. Since the great vessels at the heart would be open in the case of a removal, the victim would bleed out very quickly, but the muscle contractions of the Carotid artery feeding the brain would keep the brain supplied with blood for a little while until blood pressure was no longer sufficient for blood flow to take place. So, probably about a minute until the heartless one couldn't respond to stimuli and an unknown amount of time until consciousness faded and stimuli could no longer be sensed. If, on the other hand, the great vessels were instantly connected in such a way as to permit normal blood flow and zero blood loss, the contractions of arteries would allow the heartless one to live much longer, especially if they laid down to take the vertical pumping load away (the amount of energy required to pump blood from the bottoms of your feet to the top of your scalp is amazing).