Resistance to conventional cardiopulmonary resuscitation in witnessed out-of-hospital cardiac arrest patients with shockable initial cardiac rhythm

BackgroundShockable initial cardiac rhythm is a key predictor of survival after out-of-hospital cardiac arrest (OHCA). However, not all patients with shockable OHCA achieve return of spontaneous circulation (ROSC) via conventional cardiopulmonary resuscitation (CPR). Therefore, we retrospectively analyzed patients with witnessed OHCA and shockable initial cardiac rhythm to identify the resistance factors for conventional CPR.MethodsWe retrospectively analyzed consecutive patients with witnessed OHCA and shockable initial cardiac rhythm who were admitted to our hospital between October 2009 and October 2014. We then compared the baseline characteristics, pre-hospital clinical course, and causes of the cardiopulmonary arrest among patients who achieved ROSC via conventional CPR and patients who did not achieve ROSC via conventional CPR and underwent extracorporeal CPR (ECPR).ResultsA total of 85 patients achieved ROSC via conventional CPR (non-ECPR group) and 40 patients did not achieve ROSC via conventional CPR and underwent ECPR (ECPR group). Among these 125 patients, 113 had known causes for their cardiopulmonary arrest, including 66 cases (53%) of acute myocardial infarction (AMI). There were no significant differences in the causes of arrest between the non-ECPR and ECPR cases. However, among the 66 cases of AMI (43 non-ECPR and 23 ECPR), the rate of non-recanalization during the initial coronary angiography was significantly higher among the ECPR cases (non-ECPR: 58% vs. ECPR: 87%; p = 0.03).ConclusionsThe major cause of witnessed OHCA with shockable initial cardiac rhythm was AMI, and resistance to conventional CPR was related to continuous myocardial ischemia.