A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether it is acceptable to delay cardiopulmonary resuscitation if a patient arrests after cardiac surgery in order to attempt defibrillation or pacing, prior to performing external cardiac massage. Altogether 550 papers were found in Medline and 990 in Embase using the reported search, of which 22 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that current resuscitation guidelines state that there is no evidence to support or refute external cardiac massage prior to defibrillation in-hospital, although a benefit has been shown for patients out-of-hospital if the response time is over 4-5 min. In addition, four large studies including the AHA National Registry of Cardiopulmonary Resuscitation, who reported the findings of 6789 in-hospital arrests, emphasise the importance of early defibrillation within 1-2 min. More concerning in patients post-cardiac surgery are four case reports after cardiothoracic surgery and five in the non-surgical literature where significant harm has been caused from external cardiac massage, although equally we found cohort studies of cardiac surgical patients who had external cardiac massage followed by re-sternotomy and found no trauma due to external cardiac massage. We recommend that guidelines for immediate external massage should be adhered to currently as the evidence that these guidelines may do harm is not yet strong enough to recommend a change in practice. However, we acknowledge that there are no in-hospital data to support very short periods of external massage prior to defibrillation and there have been examples of damage to the myocardium due to external massage. This should be borne in mind when external massage is being performed on a patient after cardiac surgery.