The sooner cryopreservation is started, the better the expected outcome. Cryonics procedures should ideally begin within the first one or two minutes after the heart stops, after pronouncement of legal death, and preferably within 15 minutes. Longer delays place a greater burden on future technology to reverse injury and restore the brain to a healthy state. This makes it more uncertain that the correct original state can be determined. Exactly when such restoration is no longer feasible is a matter of some debate. The greatest impact of delay is that it degrades the circulatory system, reducing the ability to circulate chemicals that reduce freezing injury.