Abstract P35: Incidence of Re-arrest After Return of Spontaneous Circulation in Out-of-Hospital Cardiac Arrest
BACKGROUND: Return of spontaneous circulation (ROSC) occurs in approximately 30% of EMS-treated out-of-hospital cardiac arrests (OOHCA). The incidence of re-arrest (RA) before reaching the hospital is unknown, and ECG waveform variability that precedes RA has not been described.
OBJECTIVES: We sought to determine the incidence of RA in OOHCA, to classify RA events by type, and to characterize the ECG waveforms preceding RA.
METHODS: The Pittsburgh Regional Clinical Center of the NHLBI-sponsored Resuscitation Outcomes Consortium (ROC) provided the non-clinical trial data for this study. We analyzed defibrillator-monitor ECG tracings (Philips MRX) from EMS-treated cases of OOHCA cases from 2006 – 08, patient care reports (PCR) and audio recordings. Cases had to have adequate ECG before and after each ROSC/RA event to be included. We defined ROSC as audibly noted pulses and/or ECG findings indicative of pulse corroborated by PCR. We defined RA as audibly noted loss of pulses, visually identified VF or asystole, or any rhythm with resumption of CPR. Results are reported in raw numbers, followed by percentage and 95% confidence intervals in parentheses.
RESULTS: ROSC occurred in 329/1199 patients (27.4%, 25.0– 30.0%). Of these, 117 had adequate ECG. 73/117 cases did not have RA (62%, 53- 71%). RA occurred in 44 patients (38%, 29- 47%), having total of 76 RA events. Of the 44 RA cases, 24 (55%, 40 – 69%) were alive upon hospital arrival. RA events by type were: 23 refibrillation (30%, 21– 41%), 19 pulseless VT (25%, 16– 36%), 9 PEA (12%, 6– 21%), 6 asystole (8%, 3– 16%), and 18 cases of probable PEA where pulselessness could not be confirmed (24%, 15%–34%). All cases of refibrillation were preceded by ectopy, (e.g. PVCs, runs of VT) often over the course of several minutes. T wave variability, R-R interval variability, and R-on-T phenomenon were also noted to precede refibrillation. Hypoventilation (based on ETCO2) was the suspected cause of 4 nonfibrillatory RA events.
CONCLUSION: In this sample, the incidence of RA was 38%. Of cases experiencing RA 55% survived to hospital admission. Refibrillation (35%) and pulseless VT (20%) accounted the majority of RA. All cases of VF and VT RA were preceded by ectopic activity. The ECG almost always provides evidence of impending RA.