How long can your heart be stopped before cpr will no longer be successful?

No Absolute Time Cap: As in respiratory failure, CPR results depend upon the condition of the patient, the cause of the problem, "time down", the end organ damage & the effectiveness & conditions of the resuscitation. Full recovery may be possible after minutes to hours of cpr. But, as a rule, after cardiac arrest, outcomes are not good, unless effective resuscitation is accomplished rapidly ... Within minutes.Mfm.

Fairly long: If CPR is being done correctly, that is the blood is being circulated through the lungs which are being ventilated, it can go on for some time depending on the reasons for the cardiac arrest. I have done CPR for up to an hour on some patients who have survived. Ultimately, a perfusing heart rhythm must be restored and the underlying process must be reversible.