Abstract 20061: Towards Predicting the Rate and Rhythm of Rearrest After Out-of-hospital Cardiac Arrest

Background/Aims: Rearrest (RA) after resuscitation from out-of-hospital cardiac arrest (OHCA) has been shown to be an independent predictor of death before hospital discharge. The aim of this study was to understand how heart rate and rhythm transitions relate to the timing and presentation of rearrest. Methods: Case data for emergency medical services (EMS)-treated OHCA were obtained from the Resuscitation Outcomes Consortium (ROC) for the period 2006-2008. Cases with analyzable electrocardiogram (ECG) signals were included in the study. RA events were ascertained by an inferential scheme involving the presence of a life-threatening ECG rhythm and/or presence of chest compressions. ROSC-RA ECG intervals were extracted from defibrillator source files and imported into custom software for calculation of several heart rate characteristics for 30s, 1min, 3min, and 5min epochs beginning at the onset of ROSC, including: mean heart rate, standard deviation for heart rate (SD-HR), root mean square of the successive differences (RMSSD), and approximate entropy of heart rate (ApEn). Frequency-based heart rate variability measures including normalized high frequency power (HFN), normalized low frequency power (LFN), and ratio of low and high frequency power (LFHF) were calculated. Multivariable generalized estimating equations (GEE) were used to assess the relationship between heart rate characteristics and time-to-RA while controlling for RA event number, presenting OHCA ECG rhythm, and RA ECG rhythm. Rhythm transitions were assessed and compared with Fisher’s exact test. Results: In univariate analyses RMSSD in the 30s and 1-minute epoch epochs, SD-HR in the 5-minute epoch, ApEn in the 5-minute epoch, presenting ECG rhythm ventricular fibrillation / ventricular tachycardia (VF/VT), and RA event number were predictive of time-to-RA. In a multivariable model, only SD-HR in the 5-minute epoch was related to time-to-RA (coeff. = -764.16; 95%CI: -1405.92 , -122.40; p = 0.020). The most common first rhythm transition was from VF/VT to VF/VT. Conclusions: At least one heart rate-derived measure, SD-HR, was related to time-to-RA event, independent of RA ECG rhythm, presenting OHCA ECG rhythm or RA event number.