Abstract 144: Differing Pattern of ECG Changes During Resuscitation From Pulseless Electrical Activity Depending on Etiology

Introduction: Pulseless electrical activity (PEA) is a frequent initial rhythm in in-hospital cardiac arrest. ECG changes during cardiopulmonary resuscitation (CPR) have been linked to prognosis; QRS complex narrowing and increase in QRS-rate/heart rate was observed before return of spontaneous circulation (ROSC). Our hypothesis was that ECG changes during CPR of patients with cardiac arrest with initial PEA could also be different depending on etiology of arrest. Methods: Patients with cardiac arrest with initial PEA at St. Olav University Hospital (Trondheim, Norway) between January 2009 and January 2012 were prospectively included. QRS duration and heart rate were measured at all pauses in chest compressions. Etiologies were categorized as ‘Cardiac’ or ‘Other’. Trends in the material were inspected using additive mixed effects models for the last 18 minutes before ROSC or end of CPR and development of QRS width was analyzed using linear mixed effects models based on these trends. Results: A total of 63 patients for whom a reliable cause of arrest could be identified retrospectively were included. 1844 combined measurements of QRS width and heart rate were made. According to the additive mixed effects model the development in heart rate was similar in both etiology groups. The change in QRS width differed in patients who obtained ROSC, with the Cardiac group narrowing more than the other group, and both groups ending at essentially the same QRS widths at ROSC (figure). By the linear mixed effects model this difference in change was statistically significant (p=0.04). In patients who did not have ROSC, the cardiac group had significantly (p=0.001, linear mixed effects model) wider QRS complexes, but the change towards ROSC was the same in both groups. Conclusion: During the last 18 minutes before ROSC ECG characteristics differed depending on etiology, with cardiac etiologies having wider QRS complexes in the no-ROSC groups and narrowing more towards ROSC in the ROSC groups.